2005 : WHAT DO YOU BELIEVE IS TRUE EVEN THOUGH YOU CANNOT PROVE IT?

Science Historian; Author, Turing's Cathedral: The Origins of the Digital Universe; Darwin Among the Machines
Science Historian; Author, Project Orion

Interspecies coevolution of languages on the Northwest Coast.

During the years I spent kayaking along the coast of British Columbia and Southeast Alaska, I observed that the local raven populations spoke in distinct dialects, corresponding surprisingly closely to the geographic divisions between the indigenous human language groups. Ravens from Kwakiutl, Tsimshian, Haida, or Tlingit territory sounded different, especially in their characteristic "tok" and "tlik."

I believe this correspondence between human language and raven language is more than coincidence, though this would be difficult to prove.

Professor of Psychology at Harvard University
Psychologist, Harvard University

In the not too distant future, we will be able to construct artificial systems that give every appearance of consciousness—systems that act like us in every way. These systems will talk, walk, wink, lie, and appear distressed by close elections. They will swear up and down that they are conscious and they will demand their civil rights. But we will have no way
to know whether their behavior is more than a clever trick—more than the pecking of a pigeon that has been trained to type "I am, I am!"

We take each other's consciousness on faith because we must, but after two thousand years of worrying about this issue, no one has ever devised a definitive test of its existence. Most cognitive scientists believe that consciousness is a phenomenon that emerges from the complex interaction of decidedly nonconscious parts (neurons), but even when we finally understand the nature of that complex interaction, we still won't be able to prove that it produces the phenomenon in question. And yet, I haven't the slightest doubt that everyone I know has an inner life, a subjective experience, a sense of self, that is very much like mine.

What do I believe is true but cannot prove? The answer is: You!

Psychologist and Biologist, Harvard University: Author, Moral Minds
Psychologist, Harvard University: Author, Wild Minds

What makes humans uniquely smart?

Here's my best guess: we alone evolved a simple computational trick with far reaching implications for every aspect of our life, from language and mathematics to art, music and morality. The trick: the capacity to take as input any set of discrete entities and recombine them into an infinite variety of meaningful expressions.

Thus, we take meaningless phonemes and combine them into words, words into phrases, and phrases into Shakespeare. We take meaningless strokes of paint and combine them into shapes, shapes into flowers, and flowers into Matisse's water lilies. And we take meaningless actions and combine them into action sequences, sequences into events, and events into homicide and heroic rescues.

I'll go one step further: I bet that when we discover life on other planets, that although the materials may be different for running the computation, that they will create open ended systems of expression by means of the same trick, thereby giving birth to the process of universal computation.

Emeritus Professor of Psychology, London School of Economics; Visiting Professor of Philosophy, New College of the Humanities; Senior Member, Darwin College, Cambridge; Author, Soul Dust
Psychologist, London School of Economics; Author, The Mind Made Flesh

I believe that human consciousness is a conjuring trick, designed to fool us into thinking we are in the presence of an inexplicable mystery. Who is the conjuror and why is s/he doing it? The conjuror is natural selection, and the purpose has been to bolster human self-confidence and self-importance—so as to increase the value we each place on our own and others' lives.

If this is right, it provides a simple explanation for why we, as scientists or laymen, find the "hard problem" of consciousness just so hard. Nature has meant it to be hard. Indeed "mysterian" philosophers—from Colin McGinn to the Pope—who bow down before the apparent miracle and declare that it's impossible in principle to understand how consciousness could arise in a material brain, are responding exactly as Nature hoped they would, with shock and awe.

Can I prove it? It's difficult to prove any adaptationist account of why humans experience things the way they do. But here there is an added catch. The Catch-22 is that, just to the extent that Nature has succeeded in putting consciousness beyond the reach of rational explanation, she must have undermined the very possibility of showing that this is what she's done.

But nothing's perfect. There may be a loophole. While it may seem—and even be—impossible for us to explain how a brain process could have the quality of consciousness, it may not be at all impossible to explain how a brain process could (be designed to) give rise to the impression of having this quality. (Consider: we could never explain why 2 + 2 = 5, but we might relatively easily be able to explain why someone should be under the illusion that 2 + 2 = 5).

Do I want to prove it? That's a difficult one. If the belief that consciousness is a mystery is a source of human hope, there may be a real danger that exposing the trick could send us all to hell.

Hobbs Professor of Cognition and Education, Harvard Graduate School of Education; Author,Truth, Beauty, and Goodness Reframed
Psychologist, Harvard University; Author, Changing Minds

The Brain Basis of Talent

I believe that human talents are based on distinct patterns of brain connectivity. These patterns can be observed as the individual encounters and ultimately masters an organized activity or domain in his/her culture.

Consider three competing accounts:

#1 Talent is a question of practice. We could all become Mozarts or Einsteins if we persevered.

#2 Talents are fungible. A person who is good in one thing could be good in everything. 

#3 The basis of talents is genetic. While true, this account misleadingly implies that a person with a "musical gene" will necessarily evince her musicianship, just as she evinces her eye color or, less happily, Huntington's disease.

My Account: The most apt analogy is language learning. Nearly all of us can easily master natural languages in the first years of life. We might say that nearly all of us are talented speakers. An analogous process occurs with respect to various talents, with two differences:

1. There is greater genetic variance in the potential to evince talent in areas like music, chess, golf, mathematics, leadership, written (as opposed to oral) language, etc. 

2. Compared to language, the set of relevant activities is more variable within and across cultures. Consider the set of games. A person who masters chess easily in culture l, would not necessarily master poker or 'go' in culture 2.

As we attempt to master an activity, neural connections of varying degrees of utility or disutility form. Certain of us have nervous systems that are predisposed to develop quickly along the lines needed to master specific activities (chess) or classes of activities (mathematics) that happen to be available in one or more cultures. Accordingly, assuming such exposure, we will appear talented and become experts quickly. The rest of us can still achieve some expertise, but it will take longer, require more effective teaching, and draw on intellectual faculties and brain networks that the talented person does not have to use.

This hypothesis is currently being tested by Ellen Winner and Gottfried Schlaug. These investigators are imaging the brains of young students before they begin music lessons and for several years thereafter. They also are imaging control groups and administering control (non-music) tasks. After several years of music lessons, judges will determine which students have musical "talent." The researchers will document the brains of musically talented children before training, and how these brains develop.

If Account #1 is true, hours of practice will explain all. If #2 is true, those best at music should excel at all activities. If #3 is true, individual brain differences should be observable from the start. If my account is true, the most talented students will be distinguished not by differences observable prior to training but rather by the ways in which their neural connections alter during the first years of training.

Executive Director, H-STAR Institute, Stanford University; Author, The Man of Numbers: Fibonacci's Arithmetic Revolution
Mathematician, Stanford University; Author, The Millennium Problems

Before we can answer this question we need to agree what we mean by proof. (This is one of the reasons why its good to have mathematicians around. We like to begin by giving precise definitions of what we are going to talk about, a pedantic tendency that sometimes drives our physicist and engineering colleagues crazy.) For instance, following Descartes, I can prove to myself that I exist, but I can't prove it to anyone else. Even to those who know me well there is always the possibility, however remote, that I am merely a figment of their imagination. If it's rock solid certainty you want from a proof, there's almost nothing beyond our own existence (whatever that means and whatever we exist as) that we can prove to ourselves, and nothing at all we can prove to anyone else. 

Mathematical proof is generally regarded as the most certain form of proof there is, and in the days when Euclid was writing his great geometry textElements that was surely true in an ideal sense. But many of the proofs of geometric theorems Euclid gave were subsequently found out to be incorrect—David Hilbert corrected many of them in the late nineteenth century, after centuries of mathematicians had believed them and passed them on to their students—so even in the case of a ten line proof in geometry it can be hard to tell right from wrong.

When you look at some of the proofs that have been developed in the last fifty years or so, using incredibly complicated reasoning that can stretch into hundreds of pages or more, certainty is even harder to maintain. Most mathematicians (including me) believe that Andrew Wiles proved Fermat's Last Theorem in 1994, but did he really? (I believe it because the experts in that branch of mathematics tell me they do.)

In late 2002, the Russian mathematician Grigori Perelman posted on the Internet what he claimed was an outline for a proof of the Poincare Conjecture, a famous, century old problem of the branch of mathematics known as topology. After examining the argument for two years now, mathematicians are still unsure whether it is right or not. (They think it "probably is.")

Or consider Thomas Hales, who has been waiting for six years to hear if the mathematical community accepts his 1998 proof of astronomer Johannes Keplers 360-year-old conjecture that the most efficient way to pack equal sized spheres (such as cannonballs on a ship, which is how the question arose) is to stack them in the familiar pyramid-like fashion that greengrocers use to stack oranges on a counter. After examining Hales' argument (part of which was carried out by computer) for five years, in spring of 2003 a panel of world experts declared that, whereas they had not found any irreparable error in the proof, they were still not sure it was correct.

With the idea of proof so shaky—in practice—even in mathematics,answering this year's Edge question becomes a tricky business. The best we can do is come up with something that we believe but cannot prove to our own satisfaction. Others will accept or reject what we say depending on how much credence they give us as a scientist, philosopher, or whatever, generally basing that decision on our scientific reputation and record of previous work. At times it can be hard to avoid the whole thing degenerating into a slanging match. For instance, I happen to believe, firmly, that staples of popular-science-books and breathless TV-specials such as ESP and morphic resonance are complete nonsense, but I can't prove they are false. (Nor, despite their repeated claims to the contrary, have the proponents of those crackpot theories proved they are true, or even worth serious study, and if they want the scientific community to take them seriously then the onus if very much on them to make a strong case, which they have so far failed to do.)

Once you recognize that proof is, in practical terms, an unachievable ideal, even the old mathematicians standby of GÏdel's Incompleteness Theorem (which on first blush would allow me to answer the Edge question with a statement of my belief that arithmetic is free of internal contradictions) is no longer available. GÏdel's theorem showed that you cannot prove an axiomatically based theory like arithmetic is free of contradiction within that theory itself. But that doesn't mean you can't prove it in some larger, richer theory. In fact, in the standard axiomatic set theory, you can prove arithmetic is free of contradictions. And personally, I buy that proof. For me, as a living, human mathematician, the consistency of arithmetic has beenproved—to my complete satisfaction.

So to answer the Edge question, you have to take a common sense approach to proof—in this case proof being, I suppose, an argument that would convince the intelligent, professionally skeptical, trained expert in the appropriate field. In that spirit, I could give any number of specific mathematical problems that I believe are true but cannot prove, starting with the famous Riemann Hypothesis. But I think I can be of more use by using my mathematician's perspective to point out the uncertainties in the idea of proof. Which I believe (but cannot prove) I have.

Physicist, Columbia University; Author, A Madman Dreams of Turing Machines
Physicist, Columbia University; Author, How The Universe Got Its Spots

I believe there is an external reality and you are not all figments of my imagination. My friend asks me through the steam he blows off the surface of his coffee, how I can trust the laws of physics back to the origins of the universe. I ask him how he can trust the laws of physics down to his cup of coffee. He shows every confidence that the scalding liquid will not spontaneously defy gravity and fly up in his eyes. He lives with this confidence born of his empirical experience of the world. His experiments with gravity, heat, and light began in childhood when he palpated the world to test its materials. Now he has a refined and well-developed theory of physics, whether expressed in equations or not.

I simultaneously believe more and less than he does. It is rational to believe what all of my empirical and logical tests of the world confirm—that there is a reality that exists independent of me. That the coffee will not fly upwards. But it is a belief nonetheless. Once I've gone that far, why stop at the perimeter of mundane experience? Just as we can test the temperature of a hot beverage with a tongue, or a thermometer, we can test the temperature of the primordial light left over from the big bang. One is no less real than the other simply because it is remarkable.

But how do I really know? If I measure the temperature of boiling water, all I really know is that mercury climbs a glass tube. Not even that, all I really know is that I see mercury climb a glass tube. But maybe the image in my mind's eye isn't real. Maybe nothing is real, not the mercury, not the glass, not the coffee, not my friend. They are all products of a florid imagination. There is no external reality, just me. Einstein? My creation. Picasso? My mind's forgery. But this solopsism is ugly and arrogant. How can I know that mathematics and the laws of physics can be reasoned down to the moment of creation of time, space, the entire universe? In the very same way that my friend believes in the reality of the second double cappuccino he orders. In formulating our beliefs, we are honest and critical and able to admit when we are wrong—and these are the cornerstones of truth.

When I leave the café, I believe the room of couches and tables is still on the block at 122nd Street, that it is still full of people, and that they haven't evaporated when my attention drifts away. But if I am wrong and there is no external reality, then not only is this essay my invention, but so is the web,edge.org, all of its participants and their ingenious ideas. And if you are reading this, I have created you too. But if I am wrong and there is no external reality, then maybe it is me who is a figment of your imagination and the cosmos outside your door is your magnificent creation.

Physicist; Cosmologist, ASU; Author, A Universe from Nothing
Physicist, Case Western Reserve University; Author, Atom

I believe our universe is not unique. As science has evolved, our place within the universe has continued to diminish in significance.

First it was felt that the Earth was the center of the universe, then that our Sun was the center, and so on. Ultimately we now realize that we are located at the edge of a random galaxy that is itself located nowhere special in a large, potentially infinite universe full of other galaxies. Moreover, we now know that even the stars and visible galaxies themselves are but an insignificant bit of visible pollution in a universe that is otherwise dominated by 'stuff' that doesn't shine.

Dark matter dominates the masses of galaxies and clusters by a factor of 10 compared to normal matter. And now we have discovered that even matter itself is almost insignificant. Instead empty space itself contains more than twice as much energy as that associated with all matter, including dark matter, in the universe. Further, as we ponder the origin of our universe, and the nature of the strange dark energy that dominates it, every plausible theory that I know of suggests that the Big Bang that created our visible universe was not unique. There are likely to be a large, and possibly infinite number of other universes out there, some of which may be experiencing Big Bangs at the current moment, and some of which may have already collapsed inward into Big Crunches. From a philosophical perspective this may be satisfying to some, who find a universe with a definite beginning but no definite end dissatisfying. In this case, in the 'metaverse', or 'multiverse' things may seem much more uniform in time.

At every instant there may be many universes being born, and others dying. But philosophy aside, the existence of many different causally disconnected universes—regions with which we will never ever be able to have direct communication, and thus which will forever be out of reach of direct empirical verification—may have significant impacts on our understanding of our own universe. Their existence may help explain why our own universe has certain otherwise unexpected features, because in a metaverse with a possibly infinite number of different universes, which may themselves vary in their fundamental features, it could be that life like our own would evolve in only universes with a special set of characteristics.

Whether or not this anthropic type of argument is necessary to understand our universe—and I personally hope it isn't—I nevertheless find it satisfying to think that it is likely that not only are we not located in a particularly special place in our universe, but that our universe itself may be relatively insignificant on a larger cosmic scale. It represents perhaps the ultimate Copernican Revolution.

Felix Bloch Professor in Theoretical Physics, Stanford; Author, The Cosmic Landscape; The Black Hole Wars
Physicist, Stanford University

Conversation With a Slow Student

Student: Hi Prof. I've got a problem. I decided to do a little probability experiment—you know, coin flipping—and check some of the stuff you taught us. But it didn't work.

Professor: Well I'm glad to hear that you're interested. What did you do?

Student: I flipped this coin 1,000 times. You remember, you taught us that the probability to flip heads is one half. I figured that meant that if I flip 1,000 times I ought to get 500 heads. But it didn't work. I got 513. What's wrong?

Professor: Yeah, but you forgot about the margin of error. If you flip a certain number of times then the margin of error is about the square root of the number of flips. For 1,000 flips the margin of error is about 30. So you were within the margin of error.

Student: Ah, now I get if. Every time I flip 1,000 times I will always get something between 970 and 1,030 heads. Every single time! Wow, now that's a fact I can count on.

Professor: No, no! What it means is that you will probably get between 970 and 1,030.

Student: You mean I could get 200 heads? Or 850 heads? Or even all heads?

Professor: Probably not.

Student: Maybe the problem is that I didn't make enough flips. Should I go home and try it 1,000,000 times? Will it work better?

Professor: Probably.

Student: Aw come on Prof. Tell me something I can trust. You keep telling me what probably means by giving me more probablies. Tell me what probability means without using the word probably.

Professor: Hmmm. Well how about this: It means I would be surprised if the answer were outside the margin of error.

Student: My god! You mean all that stuff you taught us about statistical mechanics and quantum mechanics and mathematical probability: all it means is that you'd personally be surprised if it didn't work?

Professor: Well, uh...

If I were to flip a coin a million times I'd be damn sure I wasn't going to get all heads. I'm not a betting man but I'd be so sure that I'd bet my life or my soul. I'd even go the whole way and bet a year's salary. I'm absolutely certain the laws of large numbers—probability theory—will work and protect me. All of science is based on it. But, I can't prove it and I don't really know why it works. That may be the reason why Einstein said, "God doesn't play dice." It probably is.

Physicist, former President, Weizmann Institute of Science; Author, A View from the Eye of the Storm
Physicist, former President, Weizmann Institute of Science

The electron has been with us for over a century, laying the foundations to the electronic revolution and all of information technology. It is believed to be a point-like, elementary and indivisible particle. Is it?

The neutrino, more than a million times lighter than the electron, was predicted in the 1920's and discovered in the 1950's. It plays a crucial role in the creation of the stars, the sun and the heavy elements. It is elusive, invisible and weakly interacting. It is also considered fundamental and indivisible. Is it?

Quarks do not exist as free objects, except at extremely tiny distances, deep within the confines of the particles which are constructed from them. Since the 1960's we believe that they are the most fundamental indivisible building blocks of protons, neutrons and nuclei. Are they?

Nature has created two additional, totally unexplained, replicas of the electron, the neutrino and the most abundant quarks, u and d, forming three "generations" of fundamental particles. Each "generation" of particles is identical to the other two in all properties, except that the particle masses are radically different. Since each "generation" includes four fundamental particles, we end up with 12 different particles, which are allegedly indivisible, point-like and elementary. Are they?

The Atom, the nucleus and the proton, each in its own time, were considered elementary and indivisible, only to be replaced later by smaller objects as the fundamental building blocks. How can we be so arrogant as to exclude the possibility that this will happen again? Why would nature arbitrarily produce 12 different objects, with a very orderly pattern of electric charges and "color forces", with simple charge ratios between seemingly unrelated particles (such as the electron and the quark) and with a pattern of masses, which appears to be taken from the results of a lottery? Doesn't this "smell" again of further sub-particle structure?

There is absolutely no experimental evidence for a further substructure within all of these particles. There is no completely satisfactory theory which might explain how such light and tiny particles can contain objects moving with enormous energies, a requirement of quantum mechanics. This is, presumably, why the accepted "party line" of particle physicists is to assume that we already have reached the most fundamental level of the structure of matter.

For over twenty years, the hope has been that the rich spectrum of so-called fundamental particles will be explained as various modes of string vibrations and excitations. The astonishingly tiny string or membrane, rather than the point-like object, is allegedly at the bottom of the ladder describing the structure of matter. However, in spite of absolutely brilliant and ingenious mathematical work, not one experimental number has been explained in more than twenty years, on the basis of the string hypothesis.

Based on common sense and on an observation of the pattern of the known particles, without any experimental evidence and without any comprehensive theory, I have believed for many years, and I continue to believe, that the electron, the neutrino and the quarks are divisible. They are presumably made of different combinations of the same small number (two?) of more fundamental sub-particles. The latter may or may not have the string structure, and may or may not be themselves composites.

Will we live to see the components of the electron?

Neuroscientist; Affiliate Professor Emeritus, University of Washington; Author, Global Fever
Neurobiologist, University of Washington; Author, A Brief History of the Mind

Dan Dennett has it right in his comments below when he puts the emphasis on acquiring language, not having language, as a precondition for our kind of consciousness. For what it's worth, I have some (likely unproveable) beliefs about why the preschooler's acquisition of a structured language is so important for all the rest of her higher intellectual function. Besides syntax, intellect includes structured stuff such as multistage contingent planning, chains of logic, games with arbitrary rules, and our passion for discovering "how things hang together."

Many animals have some version of a critical period for tuning up sensory perception. Humans also seem to have one for structured language, judging from the experience with the deaf children of hearing parents who are not exposed to a rich sign language during the preschool years. Oliver Sacks in "Seeing Voices" described an 11-year-old boy who had been thought to be retarded but proved to be merely deaf. After a year of ASL instruction, Sacks interviewed him:

"Joseph saw, distinguished, categorized, used; he had no problems with perceptual categorization or generalization, but he could not, it seemed, go much beyond this, hold abstract ideas in mind, reflect, play, plan. He seemed completely literal—unable to juggle images or hypotheses or possibilities, unable to enter an imaginative or figurative realm.... He seemed, like an animal, or an infant, to be stuck in the present, to be confined to literal and immediate perception..."

In the first year, an infant is busy creating categories for the speech sounds she hears. By the second year, the toddler is busy picking up new words, each composed of a series of those phoneme building blocks. In the third year, she starts picking up on those typical combinations of words that we call grammar or syntax. She soon graduates to speaking long structured sentences. In the fourth year, she infers a patterning to the sentences and starts demanding proper endings for her bedtime stories. It is pyramiding, using the building blocks at the immediately subjacent level. Four levels in four years!

These years see a lot of softwiring via the pruning and enhancement of the prenatal connections between cortical neurons, partly on the basis of how useful a connection has been so far in life. Some such connections help you assemble a novel combination of words, check them for nonsense via some sort of quality control, and then—mirabile dictu—speak a sentence you've never uttered before. Some must be in workspaces that could plan not only sentences but an agenda for the weekend or a chain of logic or check out a chess move before you make it—even be tickled by structured music with its multiple interwoven melodies.

Then tuning up the workspace for structured language in the preschool years would likely carry over to those other structured aspects of intellect. That's why I like the emphasis on acquiring language as a precondition for consciousness: tuning up to sentence structure might make the child better able to perform at nonlanguage tasks which also need some structuring. Improve one, improve them all?

Is that what boosts our cleverness and intelligence? Is "our kind of consciousness" nothing but structured intellect with good quality control? Can't prove it, but it sure looks like a good candidate.

Neuroscientist, Stanford University; Author, Monkeyluv
Neuroscientist, Stanford University, Author, A Primate's Memoir

Well, of course, it is tempting to go for something like, "That the wheel, agriculture, and the Macarena were all actually invented by yetis." Or to do the sophomoric pseudo-ironic logic twist of, "That every truth can eventually be proven." Or to get up my hackles, draw up to my full height and intone, "Sir, we scientists believe in nothing that cannot be proven by the whetstone of science, verily our faith is our lack of faith," and then go off in a lab coat and a huff.

The first two aren't worth the words, and the third just isn't so. No matter how many times we read Arrowsmith, scientists are subjective humans operating in an ostensibly objective business, so there 's probably lots of things we take on faith.

So mine would be a fairly simple, straightforward case of an unjustifiable belief, namely that there is no god(s) or such a thing as a soul (whatever the religiously inclined of the right persuasion mean by that word). I'm very impressed, moved, by one approach of people on the other side of the fence. These are the believers who argue that it would be a disaster, would be the very work of Beelzebub, for it to be proven that god exists. What good would religiosity be if it came with a transparently clear contract, instead of requiring the leap of faith into an unknowable void?

So I'm taken with religious folks who argue that you not only can, but should believe without requiring proof. Mine is to not believe without requiring proof. Mind you, it would be perfectly fine with me if there were a proof that there is no god. Some might view this as a potential public health problem, given the number of people who would then run damagingly amok. But it's obvious that there's no shortage of folks running amok thanks to their belief. So that wouldn 't be a problem and, all things considered, such a proof would be a relief—many physicists, especially astrophysicists, seem weirdly willing to go on about their communing with god about the Big Bang, but in my world of biologists, the god concept gets mighty infuriating when you spend your time thinking about, say, untreatably aggressive childhood leukemia.

Finally, just to undo any semblance of logic here, I might even continue to believe there is no god, even if it was proven that there is one. A religious friend of mine once said to me that the concept of god is very useful, so that you can berate god during the bad times. But it is clear to me that I don't need to believe that there is a god in order to berate him.

Theoretical physicist; cosmologist; astro-biologist; co-Director of BEYOND, Arizona State University; principle investigator, Center for the Convergence of Physical Sciences and Cancer Biology; author, The Eerie Silence and The Cosmic Jackpot
Physicist, Macquarie University, Sydney; Author, How to Build a Time Machine

One of the biggest of the Big Questions of existence is, Are we alone in the universe? Science has provided no convincing evidence one way or the other. It is certainly possible that life began with a bizarre quirk of chemistry, an accident so improbable that it happened only once in the entire observable universe—and we are it. On the other hand, maybe life gets going wherever there are earthlike planets. We just don't know, because we have a sample of only one. However, no known scientific principle suggests an inbuilt drive from matter to life. No known law of physics or chemistry favors the emergence of the living state over other states. Physics and chemistry are, as far as we can tell, "life blind."

Yet I don't believe that life is a freak event. I think the universe is teeming with it. I can't prove it; indeed, it could be that mankind will never know the answer for sure. If we find life in our solar system, it most likely got there from Earth (or vice versa) in rocks kicked off planets by comet impacts. And to go beyond the solar system is the stuff of dreams. The best hope is that we develop instruments sensitive enough to detect life on extra-solar planets from Earth orbit. But, whilst not impossible, this is a formidable technical challenge.

So why do I think we are not alone, when we have no evidence for life beyond Earth? Not for the fallacious popular reason: "the universe is so big there must be life out there somewhere." Simple statistics shows this argument to be bogus. If life is in fact a freak chemical event, it would be so unlikely to occur that it wouldn't happen twice among a trillion trillion trillion planets. Rather, I believe we are not alone because life seems to be a fundamental, and not merely an incidental, property of nature. It is built into the great cosmic scheme at the deepest level, and therefore likely to be pervasive. I make this sweeping claim because life has produced mind, and through mind, beings who do not merely observe the universe, but have come to understand it through science, mathematics and reasoning. This is hardly an insignificant embellishment on the cosmic drama, but a stunning and unexpected bonus. Somehow life is able to link up with the basic workings of the cosmos, resonating with the hidden mathematical order that makes it tick. And that's a quirk too far for me.

Philosopher; Austin B. Fletcher Professor of Philosophy, Co-Director, Center for Cognitive Studies, Tufts University; Author, Intuition Pumps
Philosopher, Tufts University Author, Freedom Evolves

I believe, but cannot yet prove, that acquiring a human language (an oral or sign language) is a necessary precondition for consciousness–in the strong sense of there being a subject, an I, a 'something it is like something to be.' It would follow that non-human animals and pre-linguistic children, although they can be sensitive, alert, responsive to pain and suffering, and cognitively competent in many remarkable ways–including ways that exceed normal adult human competence–are not really conscious (in this strong sense): there is no organized subject (yet) to be the enjoyer or sufferer, no owner of theexperiences as contrasted with a mere cerebral locus of effects.

This assertion is shocking to many people, who fear that it would demote animals and pre-linguistic children from moral protection, but this would not follow. Whose pain is the pain occurring in the newborn infant? There is not yet anybody whose pain it is, but that fact would not license us to inflict painful stimuli on babies or animals any more than we are licensed to abuse the living bodies of people in comas who are definitely not conscious. If selfhood develops gradually, then certain types of events only gradually become experiences, and there will be no sharp line between unconscious pains (if we may call them that) and conscious pains, and both will merit moral attention. (And, of course, the truth of the empirical hypothesis is in any case strictly independent of its ethical implications, whatever they are. Those who shun the hypothesis on purely moral grounds are letting wishful thinking overrule a properly inquisitive scientific attitude. I am happy to give animals and small children "the benefit of the doubt" for moral purposes, but not for scientific purposes. Those who are shocked by my hypothesis should pause, if they can bear it, to notice that it is as just as difficult to prove its denial as its assertion. But it can, I think, be proven eventually. Here's what it will take, one way or the other:

(1) a well-confirmed model of the functional architecture of adult human consciousness, showing how long-distance pathways of re-entrant or reverberant interactions have to be laid down andsustained by the sorts of self-stimulation cascades that entrain language use;

(2) an interpretation of the dynamics of the model that explains why, absent these well-traveled pathways of neural micro habit, there is no functional unity to the nervous system–no unity to distinguish an I from a we (or a multitude) as the candidate subject(s) subserved by that nervous system;

(3) a host of further experimental work demonstrating the importance of what Thomas Metzinger calls the phenomenal model of the intentionality relation (PMIR) in enabling the sorts of experiences we consider central to our own adult consciousness. This work will demonstrate that animal cleverness never requires the abilities thus identified in humans, and that animals are in fact incapable of appreciating many things we normally take for granted as aspects of our conscious experience.

This is an empirical hypothesis, and it could just as well be proven false. It could be proven false by showing that in fact the necessary pathways functionally uniting the relevant brain systems (in the ways I claim are required for consciousness) are already provided in normal infant or fetal development, and are in fact present in, say, all mammalian nervous systems of a certain maturity. I doubt that this is true because it seems clear to me that evolution has already demonstrated that remarkable varieties of adaptive coordination can be accomplished without such hyper-unifying meta-systems, by colonies of social insects, for instance. What is it like to be an ant colony? Nothing, I submit, and I think most would agree intuitively. What is it like to be a brace of oxen? Nothing (even if it is like something to be a single ox). But then we have to take seriously the extent to which animals–not just insect colonies and reptiles, but rabbits, whales, and, yes, bats and chimpanzees–can get by with somewhat disunified brains.

Evolution will not have provided for the further abilities where they were not necessary for members of these species to accomplish the tasks their lives actually pose them. If animals were like the imaginary creatures in the fictions of Beatrix Potter or Walt Disney, they would have to be conscious pretty much the way we are. But animals are more different from us than we usually imagine, enticed as we are by these charming anthropomorphic fictions. We need these abilities to become persons, communicating individuals capable of asking and answering, requesting and forbidding and promising (and lying). But we don't need to be born with these abilities, since normal rearing will entrain the requisite neural dispositions. Human subjectivity, I am proposing, is thus a remarkable byproduct of human language, and no version of it should be extrapolated to any other species by default, any more than we should assume that the rudimentary communication systems of other species have verbs and nouns, prepositions and tenses.

Finally, since there is often misunderstanding on this score, I am not saying that all human consciousness consists in talking to oneself silently, although a great deal of it does. I am saying that the ability to talk to yourself silently, as it develops, also brings along with it the abilities to review, to muse, to rehearse, recollect, and in general engage the contents of events in one's nervous system that would otherwise have their effects in a purely "ballistic" fashion, leaving no memories in their wake, and hence contributing to one's guidance in ways that are well described as unconscious. If a nervous system can come to sustain all these abilities without having language then I am wrong.

Psychologist & Computer Scientist; Engines for Education Inc.; Author, Teaching Minds: How Cognitive Science Can Save Our Schools
Psychologist & Computer Scientist; Author, Designing World-Class E-Learning

Irrational choices.

I do not believe that people are capable of rational thought when it comes to making decisions in their own lives. People believe that are behaving rationally and have thought things out, of course, but when major decisions are made—who to marry, where to live, what career to pursue, what college to attend, people's minds simply cannot cope with the complexity. When they try to rationally analyze potential options, their unconscious, emotional thoughts take over and make the choice for them.

As an example of what I mean consider a friend of mine who was told to select a boat as a wedding present by his father in law. He chose a very peculiar boat which caused a real rift between him and his bride. She had expected a luxury cruiser, which is what his father in law had intended. Instead he selected a very rough boat that he could fashion as he chose. As he was an engineer his primary concern was how it would handle open ocean and he made sure the engines were special ones that could be easily gotten at and that the boat rode very low in the water. When he was finished he created a very functional but very ugly and uncomfortable boat.

Now I have ridden with him on his boat many times. Always he tells me about its wonderful features that make it a rugged and very useful boat. But, the other day, as we were about to start a trip, he started talking about how pretty he thought his boat was, how he liked the wood, the general placement of things, and the way the rooms fit together. I asked him if he was describing a boat that he had been familiar with as a child and suggested that maybe this boat was really a copy of some boat he knew as a kid. He said, after some thought, that that was exactly the case, there had been a boat like in his childhood and he had liked it a great deal.

While he was arguing with his father in law, his wife, and nearly everyone he knew about his boat, defending his decision with all the logic he could muster, destroying the very conceptions of boats they had in mind, the simple truth was his unconscious mind was ruling the decision making process. It wanted what it knew and loved, too bad for the conscious which had to figure how to explain this to everybody else.

Of course, psychoanalysts have made a living on trying to figure out why people make the decisions they do. The problem with psychoanalysis is that it purports to be able to cure people. This possibility I doubt very much. Freud was a doctor so I guess he got paid to fix things and got carried away. But his view of the unconscious basis of decision making was essentially correct. We do not know how we decide things, and in a sense we don't really care. Decisions are made for us by our unconscious, the conscious is in charge of making up reasons for those decisions which sound rational. We can, on the other hand, think rationally about the choices that other people make. We can do this because we do not know and are not trying to satisfy unconscious needs and childhood fantasies. As for making good decisions in our lives, when we do it is mostly random. We are always operating with too little information consciously and way too much unconsciously.

Professor of Physics, Institute for Advanced Study; Author, Many Colored Glass; The Scientist as Rebel
Physicist, Institute of Advanced Study, Author, Disturbing the Universe

Since I am a mathematician, I give a precise answer to this question. Thanks to Kurt Gödel, we know that there are true mathematical statements that cannot be proved. But I want a little more than this. I want a statement that is true, unprovable, and simple enough to be understood by people who are not mathematicians. Here it is.

Numbers that are exact powers of two are 2, 4, 8, 16, 32, 64, 128 and so on. Numbers that are exact powers of five are 5, 25, 125, 625 and so on. Given any number such as 131072 (which happens to be a power of two), the reverse of it is 270131, with the same digits taken in the opposite order. Now my statement is: it never happens that the reverse of a power of two is a power of five.

The digits in a big power of two seem to occur in a random way without any regular pattern. If it ever happened that the reverse of a power of two was a power of five, this would be an unlikely accident, and the chance of it happening grows rapidly smaller as the numbers grow bigger. If we assume that the digits occur at random, then the chance of the accident happening for any power of two greater than a billion is less than one in a billion. It is easy to check that it does not happen for powers of two smaller than a billion. So the chance that it ever happens at all is less than one in a billion. That is why I believe the statement is true.

But the assumption that digits in a big power of two occur at random also implies that the statement is unprovable. Any proof of the statement would have to be based on some non-random property of the digits. The assumption of randomness means that the statement is true just because the odds are in its favor. It cannot be proved because there is no deep mathematical reason why it has to be true. (Note for experts: this argument does not work if we use powers of three instead of powers of five. In that case the statement is easy to prove because the reverse of a number divisible by three is also divisible by three. Divisibility by three happens to be a non-random property of the digits).

It is easy to find other examples of statements that are likely to be true but unprovable. The essential trick is to find an infinite sequence of events, each of which might happen by accident, but with a small total probability for even one of them happening. Then the statement that none of the events ever happens is probably true but cannot be proved.

Senior Maverick, Wired, Author, Cool Tools; What Technology Wants; "The Three Breakthroughs That Have Finally Unleashed AI on the World" (Wired)
Editor-At-Large, Wired; Author, New Rules for the New Economy

The orthodoxy in biology states that every cell in your body shares exactly the same DNA. It's your identity, your indelible fingerprint, and since all the cells in your body have been duplicated from your initial unique stem cell these zillion of offspring cells all maintain your singular DNA sequence. It follows then that when you submit a tissue sample for genetic analysis it doesn't matter where it comes from. Normally technicians grab some from the easily accessible pars of your mouth, but they could just as well take some from your big toe, or your liver, or eyelash and get the same results.

I believe, but cannot prove, that the DNA in your body (and all bodies) varies from part to part. I make this prediction based on what we know about biology, which is that natures abhors uniformity. No where else in nature do we see identity maintained to such exactness. No where else is there such fixity.

I do not expect intra-soma variation to diverge very much. Indeed the genetic variation among individual humans is already relatively mild, among the least of all animals, so the diversity within a human body is unlikely to be greater than among human bodies—although that may be possible. More likely, intra-soma variation will be less than racial diversity but greater than zero.

Biologists already know (even if the public doesn't) that the full sequence of DNA in your cells changes over time as your chromosomes are shorten each time they divide in growth. Because of a bug in the system, DNA is unable to duplicate itself when it gets to the very very tip of its chain, so at each division it winds up a few hundred bases short. This slight reduction after each of the cell's scores of divisions is currently seen as the chief culprit in cell death and thus your own death. But the variation I believe is happening is more fundamental. My guess is that DNA mutates in a population of the cells in your body much as it does in a population of bodies.

The consequences are more than just curious. At the trivial end, if my belief were true, it would matter where you selected to sample your DNA from. And it might also affect when you get it, as this variation could change over time. If true, this variation might have some effect on locating the correct seminal cells for growing replacement organs and tissues.

While I have no evidence for my belief right now, it is a provable assertion. It will be shown to be true or false as soon as we have ubiquitous cheap full-genome sequences at discount mall prices. That is, pretty soon. I believe that once we have a constant reading of our individual full DNA (many times over our lives) we will have no end of surprises. I would not be surprised to discover that pet owners accumulate some tiny fragments of their pet's DNA,which has somehow been laterally transferred via viruses to their own cellular DNA. Or that diary farmers amass noticeable fragments of bovine DNA. Or that the DNA in our limbs somehow drift genetically in a "limby" way, distinct from the variation in the cells in our nervous systems.

But I consider all this minor compared to a possible major breakthrough in understanding. We have a pretty good idea of how the "selection" in natural selection works: less fit organisms die. But when it comes to understanding how variation arises in Darwinian evolution all we can say is "random mutation" which is another way of saying "we don't know exactly." If there were intra-somatic variation and if we could easily observe it via massive constant full-genome sequencing then we might be able to figure out exactly how a mutation occurs, and whether there are patterns to those mutations, and to what extant such variation is induced or influenced by the body or the environment—all ideas which currently challenge the Darwinian wisdom that the body does not directly influence the genetic makeup of a cell. Monitoring genetic drift within a body may be a window into the origins of mutation itself.

Even if these larger ideas don't pan out, the simple fact that DNA in each cell of your body is not 100% identical would be worth investigating. Such a fact would be a surprise, except to me.

Professor of Physics & Astronomy, University of Pennsylvania; Author, Ordinary Geniuses
Physicist, University of Pennsylvania; Author, A Matter of Degrees

The Big Bang, that giant explosion of more than 13 billion years ago, provides the accepted description of our Universe's beginning. We can trace with exquisite precision what happened during the expansion and cooling that followed that cataclysm, but the presence of neutrinos in that earliest phase continues to elude direct experimental confirmation.

Neutrinos, once in thermal equilibrium, were supposedly freed from their bonds to other particles about two seconds after the Big Bang. Since then they should have been roaming undisturbed through intergalactic space, some 200 of them in every cubic centimeter of our Universe, altogether a billion of them for every single atom. Their presence is noted indirectly in the Universe's expansion. However, though they are presumably by far the most numerous type of material particle in existence, not a single one of those primordial neutrinos has ever been detected. It is not for want of trying, but the necessary experiments are almost unimaginably difficult. And yet those neutrinos must be there. If they are not, our whole picture of the early Universe will have to be totally reconfigured.

Wolfgang Pauli's original 1930 proposal of the neutrino's existence was so daring he didn't publish it. Enrico Fermi's brilliant 1934 theory of how neutrinos are produced in nuclear events was rejected for publication byNature magazine as being too speculative. In the 1950s neutrinos were detected in nuclear reactors and soon afterwards in particle accelerators. Starting in the 1960s, an experimental tour de force revealed their existence in the solar core. Finally, in1987 a ten second burst of neutrinos was observed radiating outward from a supernova collapse that had occurred almost 200,000 years ago. When they reached the Earth and were observed, one prominent physicist quipped that extra-solar neutrino astronomy "had gone in ten seconds from science fiction to science fact". These are some of the milestones of 20th century neutrino physics.

In the 21st century we eagerly await another one, the observation of neutrinos produced in the first seconds after the Big Bang. We have been able to identify them, infer their presence, but will we be able to actually see these minute and elusive particles? They must be everywhere around us, even though we still cannot prove it.

Professor of Linguistics and Western Civilization, Columbia University; Cultural Commentator; Author, Doing Our Own Thing
Linguist, Senior Fellow, Manhattan Institute; Author, Doing Our Own Thing

This year, researching the languages of Indonesia for an upcoming book, I happened to find out about a few very obscure languages spoken on one island that are much simpler than one would expect.

Most languages are much, much more complicated than they need to be. They take on needless baggage over the millennia simply because they can. So, for instance, most languages of Indonesia have a good number of prefixes and/or suffixes. Their grammars often force the speaker to attend to nuances of difference between active and passive much more than a European languages does, etc.

But here were a few languages that had no prefixes or suffixes at all. Nor do they have any tones, like many languages in the world. For one thing, languages that have been around forever that have no prefixes, suffixes, or tones are very rare worldwide. But then, where we do find them, they are whole little subfamilies, related variations on one another. Here, though, is a handful of small languages that contrast bizarrely with hundreds of surrounding relatives.

One school of thought in how language changes says that this kind of thing just happens by chance. But my work has been showing me that contrasts like this are due to sociohistory. Saying that naked languages like this are spoken alongside ones as bedecked as Italian is rather like saying that kiwis are flightless just "because," rather than because their environment divested them of the need to fly.

But for months I scratched my head over these languages. Why just them? Why there?

So isn't it interesting that the island these languages is spoken on is none other than Flores, which has had its fifteen minutes of fame this year as the site where skeletons of the "little people" were found. Anthropologists have hypothesized that this was a different species of Homo. While the skeletons date back 13,000 years ago or more, local legend recalls "little people" living alongside modern humans, ones who had some kind of language of their own and could "repeat back" in modern humans' language.

The legends suggest that the little people only had primitive language abilities, but we can't be sure here: to the untutored layman who hasn't taken any twentieth-century anthropology or linguistics classes, it is easy to suppose that an incomprehensible language is merely babbling.

Now, I can only venture this highly tentatively now. But what I "know" but cannot prove this year is: the reason languages like Keo and Ngada are so strangely streamlined on Flores is that an earlier ancestor of these languages, just as complex as its family members tend to be, was used as second language by these other people and simplified. Just as our classroom French and Spanish avoids or streamlines a lot of the "hard stuff," people who learn a language as adults usually do not master it entirely.

Specifically, I would hypothesize that the little people were gradually incorporated into modern human society over time—perhaps subordinated in some way—such that modern human children were hearing the little people's rendition of the language as much as a native one.

This kind of process is why, for example, Afrikaans is a slightly simplified version of Dutch. Dutch colonists took on Bushmen as herders and nurses, and their children often heard second-language Dutch as much as their parents. Pretty soon, this new kind of Dutch was everyone's everyday language, and Afrikaans was born.

Much has been made over the parallels between the evolution of languages and the evolution of animals and plants. However, I believe that one important difference is that while animals and plants can evolve towards simplicity as well as complexity depending on conditions, languages do not evolve towards simplicity in any significant, overall sense—unless there is some sociohistorical factor that puts a spoke in the wheel.

So normally, languages are always drifting into being like Russian or Chinese or Navajo. They only become like Keo and Ngada—or Afrikaans, or creole languages like Papiamentu and Haitian, or even, I believe, English—because of the intervention of factors like forced labor and population relocation. Just maybe, we can now add interspecies contact to the list!

Nobel laureate physicist, Princeton
Physicist and Nobel laureate, Princeton University

Is string theory a futile exercise as physics, as I believe it to be? It is an interesting mathematical specialty and has produced and will produce mathematics useful in other contexts, but it seems no more vital as mathematics than other areas of very abstract or specialized math, and doesn't on that basis justify the incredible amount of effort expended on it.

My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance. It proposes that Nature is the way we would like it to be rather than the way we see it to be; and it is improbable that Nature thinks the same way we do.

The sad thing is that, as several young would-be theorists have explained to me, it is so highly developed that it is a full-time job just to keep up with it. That means that other avenues are not being explored by the bright, imaginative young people, and that alternative career paths are blocked.

professor of astrophysics at the Institute for Advanced Study, in Princeton
Astrophysicist, Institute of Advanced Study

Science, like most human activities, is based on a belief, namely the assumption that nature is understandable.

If we are faced with a puzzling experimental result, we first try harder to understand it with currently available theory, using more clever ways to apply that theory. If that really doesn't work, we try to improve or perhaps even replace the theory. We never conclude that a not-yet understood result is in principle un-understandable.

While some philosophers might draw a different conclusion—see the contribution by Nicholas Humphrey—as a scientist I strongly believe that Nature is understandable. And such a belief can neither be proved nor disproved.

Note: undoubtedly, the notion of what counts as "understandable" will continue to change. What physicists consider to be understandable now is very different from what had been regarded as such one hundred years ago. For example, quantum mechanics tells us that repeating the same experiment will give different results. The discovery of quantum mechanics led us to relax the rigid requirement of a deterministic objective reality to a statistical agreement with a not fully determinable reality. Although at first sight such a restriction might seem to limit our understanding, we in fact have gained a far deeper understanding of matter through the use of quantum mechanics than we could possibly have obtained using only classical mechanics.

Zellerbach Family Professor of Psychology, University of Pennsylvania; best-selling author
Psychologist, University of Pennsylvania, Author, Authentic Happiness

The "rotten-to-the-core" assumption about human nature espoused so widely in the social sciences and the humanities is wrong. This premise has its origins in the religious dogma of original sin and was dragged into the secular twentieth century by Freud, reinforced by two world wars, the Great Depression, the cold war, and genocides too numerous to list. The premise holds that virtue, nobility, meaning, and positive human motivation generally are reducible to, parasitic upon, and compensations for what is really authentic about human nature: selfishness, greed, indifference, corruption and savagery. The only reason that I am sitting in front of this computer typing away rather than running out to rape and kill is that I am "compensated," zipped up, and successfully defending myself against these fundamental underlying impulses.

In spite of its widespread acceptance in the religious and academic world, there is not a shred of evidence, not an iota of data, which compels us to believe that nobility and virtue are somehow derived from negative motivation. On the contrary, I believe that evolution has favored both positive and negative traits, and many niches have selected for morality, co-operation, altruism, and goodness, just as many have also selected for murder, theft, self-seeking, and terrorism.

More plausible than the rotten-to-the-core theory of human nature is the dual aspect theory that the strengths and the virtues are just as basic to human nature as the negative traits: that negative motivation and emotion have been selected for by zero-sum-game survival struggles, while virtue and positive emotion have been selected for by positive sum game sexual selection. These two overarching systems sit side by side in our central nervous system ready to be activated by privation and thwarting, on the one hand, or by abundance and the prospect of success, on the other.

Founding Dean, Minerva Schools at the Keck Graduate Institute
Psychologist, Harvard University; Author, Wet Mind

Mental processes: An out-of-body existence?

These days, it seems obvious that the mind arises from the b rain (not the heart, liver, or some other organ). In fact, I personally have gone so far as to claim that "the mind is what the brain does." But this notion does not preclude an unconventional idea: Your mind may arise not simply from your own brain, but in part from the brains of other people.

Let me explain. This idea rests on three key observations.

The first is that our brains are limited, and so we use crutches to supplement and extend our abilities. For example, try to multiply 756 by 312 in your head. Difficult, right? You would be happier with a pencil and piece of paper—or, better yet, an electronic calculator. These devices serve as prosthetic systems, making up for cognitive deficiencies (just as a wooden leg would make up for a physical deficiency).

The second observation is that the major prosthetic system we use is other people. We set up what I call "Social Prosthetic Systems" (SPSs), in which we rely on others to extend our reasoning abilities and to help us regulate and constructively employ our emotions. A good marriage may arise in part because two people can serve as effective SPSs for each other.

The third observation is that a key element of serving as a SPS is learning how best to help someone. Others who function as your SPSs adapt to your particular needs, desires and predilections. And the act of learning changes the brain. By becoming your SPS, a person literally lends you part of his or her brain!

In short, parts of other people's brains come to serve as extensions of your own brain. And if the mind is "what the brain does," then your mind in fact arises from the activity of not only your own brain, but those of your SPSs.

There are many implications of these ideas, ranging from reasons why we behave in certain ways toward others to foundations of ethics and even to religion. In fact, one could even argue that when your body dies, part of your mind may survive. But before getting into such dark and dusty corners, it would be nice to have firm footing—to collect evidence that these speculations are in fact worth taking seriously.

Author, The Math Book, The Physics Book, and The Medical Book Trilogy
Computer scientist, IBM's T. J. Watson Research Center; Author, Calculus and Pizza

If we believe that consciousness is the result of patterns of neurons in the brain, our thoughts, emotions, and memories could be replicated in moving assemblies of Tinkertoys. The Tinkertoy minds would have to be very big to represent the complexity of our minds, but it nevertheless could be done, in the same way people have made computers out of 10,000 Tinkertoys. In principle, our minds could be hypostatized in patterns of twigs, in the movements of leaves, or in the flocking of birds. The philosopher and mathematician Gottfried Leibniz liked to imagine a machine capable of conscious experiences and perceptions. He said that even if this machine were as big as a mill and we could explore inside, we would find "nothing but pieces which push one against the other and never anything to account for a perception."

If our thoughts and consciousness do not depend on the actual substances in our brains but rather on the structures, patterns, and relationships between parts, then Tinkertoy minds could think. If you could make a copy of your brain with the same structure but using different materials, the copy would think it was you. This seemingly materialistic approach to mind does not diminish the hope of an afterlife, of transcendence, of communion with entities from parallel universes, or even of God. Even Tinkertoy minds can dream, seek salvation and bliss—and pray.

Psychologist, UC, Berkeley; Author, The Philosophical Baby
Psychologist, UC-Berkeley; Coauthor, The Scientist In the Crib

I believe, but cannot prove, that babies and young children are actually more conscious, more vividly aware of their external world and internal life, than adults are. I believe this because there is strong evidence for a functional trade-off with development. Young children are much better than adults at learning new things and flexibly changing what they think about the world. On the other hand, they are much worse at using their knowledge to act in a swift, efficient and automatic way. They can learn three languages at once but they can't tie their shoelaces. 

This trade-off makes sense from an evolutionary perspective. Our species relies more on learning than any other, and has a longer childhood than any other. Human childhood is a protected period in which we are free to learn without being forced to act. There is even some neurological evidence for this. Young children actually have substantially more neural connections than adults—more potential to put different kinds of information together. With experience, some connections are strengthened and many others disappear entirely. As the neuroscientists say, we gain conductive efficiency but lose plasticity.

What does this have to do with consciousness? Consider the experiences we adults associate with these two kinds of functions. When we know how to do something really well and efficiently, we typically lose, or at least, reduce, our conscious awareness of that action. We literally don't see the familiar houses and streets on the well-worn route home, although, of course, in some functional sense we must be visually taking them in. In contrast, as adults when we are faced with the unfamiliar, when we fall in love with someone new, or when we travel to a new place, our consciousness of what is around us and inside us suddenly becomes far more vivid and intense. In fact, we are willing to expend lots of money, and lots of emotional energy, for those few intensely alive days in Paris or Beijing that we will remember long after months of everyday life have vanished.

Similarly, as adults when we need to learn something new, say when we learn to skydive, or work out a new scientific idea, or even deal with a new computer, we become vividly, even painfully, conscious of what we are doing—we need, as we say, to pay attention. As we become expert we need less and less attention, and we experience the actual movements and thoughts and keystrokes less and less. We sometimes say that adults are better at paying attention than children, but really we mean just the opposite. Adults are better at not paying attention. They're better at screening out everything else and restricting their consciousness to a single focus. Again there is a certain amount of brain evidence for this. Some brain areas, like the dorsolateral prefrontal cortex, consistently light up for adults when they are deeply engaged in learning something new. But for more everyday tasks, these areas light up much less. For children, though the pattern is different—these areas light up even for mundane tasks. 

I think that, for babies, every day is first love in Paris. Every wobbly step is skydiving, every game of hide and seek is Einstein in 1905.

The astute reader will note that this is just the opposite of what Dan Dennett believes but cannot prove. And this brings me to a second thing I believe but cannot prove. I believe that the problem of capital-C Consciousness will disappear in psychology just as the problem of Life disappeared in biology. Instead we'll develop much more complex, fine-grained and theoretically driven accounts of the connections between particular types of phenomenological experience and particular functional and neurological phenomena. The vividness and intensity of our attentive awareness, for example, may be completely divorced from our experience of a constant first-person I. Babies may be more conscious in one way and less in the other. The consciousness of pain may be entirely different from the consciousness of red which may be entirely different from the babbling stream of Joyce and Woolf.

Neuroscientist, New York University; Author, Synaptic Self
Neuroscientist, New York University; Author, The Synaptic Self

For me, this is an easy question. I believe that animals have feelings and other states of consciousness, but neither I, nor anyone else, has been able to prove it. We can't even prove that other people are conscious, much less other animals. In the case of other people, though, we at least can have a little confidence since all people have brains with the same basic configurations. But as soon as we turn to other species and start asking questions about feelings, and consciousness in general, we are in risky territory because the hardware is different.

When a rat is in danger, it does things that many other animals do. That is, it either freezes, runs away or fights back. People pretty much do the same things. Some scientists say that because a rat and a person act the same in similar situations, they have the same kinds of subjective experiences. I don't think we can really say this.

There are two aspects of brain hardware that make it difficult for us to generalize from our personal subjective experiences to the experiences of other animals. One is the fact that the circuits most often associated with human consciousness involve the lateral prefrontal cortex (via its role in working memory and executive control functions). This broad zone is much more highly developed in people than in other primates, and whether it exists at all in non-primates is questionable. So certainly for those aspects of consciousness that depend on the prefrontal cortex, including aspects that allow us to know who we are and to make plans and decisions, there is reason to believe that even other primates might be different than people. The other aspect of the brain that differs dramatically is that humans have natural language. Because so much of human experience is tied up with language, consciousness is often said to depend on language. If so, then most other animals are ruled out of the consciousness game. But even if consciousness doesn't depend on language, language certainly changes consciousness so that whatever consciousness another animal has it is likely to differ from most of our states of consciousness.

For these reasons, I think it is hard to know what consciousness might be like in another animal. If we can't measure it (because it is internal and subjective) and can't use our own experience to frame questions about it (because the hardware that makes it possible is different), it become difficult to study.

Most of what I have said applies mainly to the content of conscious experience. But there is another aspect of consciousness that is less problematic scientifically. It is possible to study the processes that make consciousness possible even if we can't study the content of consciousness in other animals. This is exactly what is done in studies of working memory in non-human primates. One approach by that has had some success in the area of conscious content in non-human primates has focused on a limited kind of consciousness, visual awareness. But this approach, by Koch and Crick, mainly gets at the neural correlates of consciousness rather than the causal mechanisms. The correlates and the mechanisms may be the same, but they may not. Interestingly, this approach also emphasizes the importance of prefrontal cortex in making visual awareness possible.

So what about feelings? My view is that a feeling is what happens when an emotion system, like the fear system, is active in a brain that can be aware of its own activities. That is, what we call "fear" is the mental state that we are in when the activity of the defense system of the brain (or the consequences of its activity, such as bodily responses) is what is occupying working memory. Viewed this way, feelings are strongly tied to those areas of the cortex that are fairly unique to primates and especially well developed in people. When you add natural language to the brain, in addition to getting fairly basic feelings you also get fine gradations due to the ability to use words and grammar to discriminate and categorize states and to attribute them not just to ourselves but to others.

There are other views about feelings. Damasio argues that feelings are due to more primitive activity in body sensing areas of the cortex and brainstem. Pankseep has a similar view, though he focuses more on the brainstem. Because this network has not changed much in the course of human evolution, it could therefore be involved in feelings that are shared across species. I don't object to this on theoretical grounds, but I don't think it can be proven because feelings can't be measured in other animals. Pankseep argues that if it looks like fear in rats and people, it probably feels like fear in both species. But how do you know that rats and people feel the same when they behave the same? A cockroach will escape from danger--does it, too, feel fear as it runs away? I don't think behavioral similarity is sufficient grounds for proving experiential similarity. Neural similarity helps—rats and people have similar brainstems, and a roach doesn't even have a brain. But is the brainstem responsible for feelings? Even if it were proven in people, how would you prove it in a rat?

So now we're back where we started. I think rats and other mammals, and maybe even roaches (who knows?), have feelings. But I don't know how to prove it. And because I have reason to think that their feelings might be different than ours, I prefer to study emotional behavior in rats rather than emotional feelings. I study rats because you can make progress at the neural level, provided that the thing you measure is the same in rats and people. I wouldn't study language and consciousness in rats, so I don't study feelings either, because I don't know that they exist. I may be accused of being short-sighted for this, but I'd rather make progress on something I can study in rats than beat my head against the consciousness wall in these creatures.

There's lots to learn about emotion through rats that can help people with emotional disorders. And there's lots we can learn about feelings from studying humans, especially now that we have powerful function imaging techniques. I'm not a radical behaviorist. I'm just a practical emotionalist.

Psychologist; Author, Consciousness: An Introduction
Psychologist, Visiting Lecturer, University of the West of England, Bristol; Author The Meme Machine

It is possible to live happily and morally without believing in free will. As Samuel Johnson said "All theory is against the freedom of the will; all experience is for it." With recent developments in neuroscience and theories of consciousness, theory is even more against it than it was in his time, more than 200 years ago. So I long ago set about systematically changing the experience. I now have no feeling of acting with free will, although the feeling took many years to ebb away.

But what happens? People say I'm lying! They say it's impossible and so I must be deluding myself to preserve my theory. And what can I do or say to challenge them? I have no idea—other than to suggest that other people try the exercise, demanding as it is.

When the feeling is gone, decisions just happen with no sense of anyone making them, but then a new question arises—will the decisions be morally acceptable? Here I have made a great leap of faith (or the memes and genes and world have done so). It seems that when people throw out the illusion of an inner self who acts, as many mystics and Buddhist practitioners have done, they generally do behave in ways that we think of as moral or good. So perhaps giving up free will is not as dangerous as it sounds—but this too I cannot prove.

As for giving up the sense of an inner conscious self altogether—this is very much harder. I just keep on seeming to exist. But though I cannot prove it—I think it is true that I don't.

Johnstone Family Professor, Department of Psychology; Harvard University; Author, The Better Angels of Our Nature
Psychologist, Harvard University; Author, The Blank Slate

In 1974, Marvin Minsky wrote that "there is room in the anatomy and genetics of the brain for much more mechanism than anyone today is prepared to propose." Today, many advocates of evolutionary and domain-specific psychology are in fact willing to propose the richness of mechanism that Minsky called for thirty years ago. For example, I believe that the mind is organized into cognitive systems specialized for reasoning about object, space, numbers, living things, and other minds; that we are equipped with emotions triggered by other people (sympathy, guilt, anger, gratitude) and by the physical world (fear, disgust, awe); that we have different ways for thinking and feeling about people in different kinds of relationships to us (parents, siblings, other kin, friends, spouses, lovers, allies, rivals, enemies); and several peripheral drivers for communicating with others (language, gesture, facial expression).

When I say I believe this but cannot prove it, I don't mean that it's a matter of raw faith or even an idiosyncratic hunch. In each case I can provide reasons for my belief, both empirical and theoretical. But I certainly can't prove it, or even demonstrate it in the way that molecular biologists demonstrate their claims, namely in a form so persuasive that skeptics can't reasonably attack it, and a consensus is rapidly achieved. The idea of a richly endowed human nature is still unpersuasive to many reasonable people, who often point to certain aspects of neuroanatomy, genetics, and evolution that appear to speak against it. I believe, but cannot prove, that these objections will be met as the sciences progress.

At the level of neuroanatomy and neurophysiology, critics have pointed to the apparent homogeneity of the cerebral cortex and of the seeming interchangeability of cortical tissue in experiments in which patches of cortex are rewired or transplanted in animals. I believe that the homogeneity is an illusion, owing to the fact that the brain is a system for information processing. Just as all books look the same to someone who does not understand the language in which they are written (since they are all composed of different arrangements of the same alphanumeric characters), and the DVD's of all movies look the same under a microscope, the cortex may look homogeneous to the eye but nonetheless contain different patterns of connectivity and synaptic biases that allow it to compute very different functions. I believe this these differences will be revealed in different patterns of gene expression in the developing cortex. I also believe that the apparent interchangeability of cortex occurs only in early stages of sensory systems that happen to have similar computational demands, such as isolating sharp signal transitions in time and space.

At the level of genetics, critics have pointed to the small number of genes in the human genome (now thought to be less than 25,000) and to their similarity to those of other animals. I believe that geneticists will find that there is a large store of information in the noncoding regions of the genome (the so-called junk DNA), whose size, spacing, and composition could have large effects on how genes are expressed. That is, the genes themselves may code largely for the meat and juices of the organism, which are pretty much the same across species, whereas how they are sculpted into brain circuits may depend on a much larger body of genetic information. I also believe that many examples of what we call "the same genes" in different species may differ in tiny ways at the sequence level that have large consequences for how the organism is put together.

And at the level of evolution, critics have pointed to how difficult it is to establish the adaptive function of a psychological trait. I believe this will change as we come to understand the genetic basis of psychological traits in more detail. New techniques in genomic analysis, which look for statistical fingerprints of selection in the genome, will show that many genes involved in cognition and emotion were specifically selected for in the primate, and in many cases the human, lineage.

Physicist, Director, MIT's Center for Bits and Atoms; Author, FAB
Physicist, MIT; Author, When Things Start to Think

What do you believe is true even though you cannot prove it?

Progress. 

The enterprise that employs me, seeking to understand and apply insight into how the world works, is ultimately based on the belief that this is a good thing to do. But it's something of a leap of faith to believe that that will leave the world a better place—the evidence to date is mixed for technical advances monotonically mapping onto human advances.

Naturally, this question has a technical spin for me. My current passion is the creation of tools for personal fabrication based on additive digital assembly, so that the uses of advanced technologies can be defined by their users. It's still no more than an assumption that that will lead to more good things than bad things being made, but, like the accumulated experience that democracy works better than monarchy, I have more faith in a future based on widespread access to the means for invention than one based on technocracy.

Computer Scientist; Musician; Author, Who Owns The Future?
Computer Scientist and Musician

My career has been guided by just the sort of unproven guess this year's question seeks.

My belief is that the potential for expanded communication between people far exceeds the potential both of language as we think of it (the stuff we say, read and write) and of all the other communication forms we already use.

Suppose for a moment that children in the future will grow up with an easy and intimate virtual reality technology and that their use of it will become focused on invention and design instead of the consumption of pre-created holo-video games, surround movies, or other content.

Maybe these future children will play virtual musical instrument-like things that cause simulated trees and spiders and seasons and odors and ecologies to spring up just as manipulating a pencil causes words to appear on a page. If people grew up with a virtuosic ability to improvise the contents of a shared virtual world, a new sort of communication might also appear.

It's barely possible to imagine what a "reality conversation" would be like. Each person would be changing the shared world at the speed of language, all at once, an image that suggests chaos, but often there would be a coherence, which would indicate meaning. A kid becomes a monster, eats his little brother, who becomes a vitriolic turd, and so on.

This is what I've called "Post-symbolic communication," though really it won't exist in isolation of or in opposition to symbolic communication techniques. It will be something different, however, and will expand what people can mean to each other.

Post-symbolic communication will be like a shared, waking state, intentional dream. Instead of the word "house", you will express a particular house and be able to walk into it, and instead of the category "house" you will peer into an apparently small bucket that is big enough inside to hold all the universe's houses so you can assess what they have in common directly. It will be a fluid form of experiential concreteness providing similar but divergent expressive power to that of abstraction.

Why care? The acquisition of post-symbolic communication will be a centuries-long adventure, an expansion of meaning, something beautiful, and a way to seek cool, advanced technology that focuses on connection instead of mere power. It will be a form of beauty which also enhances survivability; Since the drive for "cool tech" is unstoppable, the invention of provocative cool tech that is lovely enough to seduce the attention of young smart men away from arms races is a prerequisite to the survival of the species.

Some of the examples above (houses, spiders) are of people improvising the external environment, but post-symbolic communication might typically look a lot more like people morphing themselves into varied forms. Experiments have already been conducted with kids wearing special body suits and goggles "turning into" triangles to learn trigonometry, or molecules to learn chemistry.

It's not only the narcissism of the young (and not so young) human mind or the primality of the control of one's own body that makes self-transformation compelling. Evolution, as generous as she ended up being with us humans, was stingy with potential means of expression. Compare us with the mimic octopus which can morph into all sorts of creatures and objects, and can animate its skin. An advanced civilization of cephalopods might develop words as we know them, but probably only as an adjunct to a natural form of post-symbolic communication.

We humans can control precious little of the world with enough agility to keep up with our thoughts and feelings. The fingers and the tongue are the about it. Symbols as we know them in language are a trick, or what programmers call a "hack," that expands the power of little appendage wiggles to refer to all that we can't instantly become or create. Another belief: The tongue that can speak could also someday control fantastic forms beyond our current imaginings. (Some early experiments along these lines have been done, using ultrasound sensing through the cheek. and the results are at least not terrible.)

While we're confessing unprovable beliefs, here's another one: The study of the genetic components of pecking order behavior, group belief cues, and clan identification leading to inter-clan hostility will be the core of psychology and sociology for the next few generations, and it will turn out we can't turn off or control these elements of human character without losing other qualities we love, like creativity. If this dark guess is correct, then the means to survival is to create societies with a huge variety of paths to success and a multitude of overlapping, intertwined clans and pecking orders, so that everyone can be a winner from equally valid individual perspectives. When the American experiment has worked best, it has approximated this level of variety. The virtual worlds of post-symbolic communication can provide the highest level of variety to satisfy the dangerous psychic inheritance I'm guessing we suffer as a species.

Implicit in the futures I am imagining here is a solution to the software crisis. If children are breathing out fully realized creatures and skies just as they form sentences today, there must be software present which isn't crashing and is marvelously flexible and responsive, yet free of limiting pre-conceptions, which would revive symbolism. Can such software exist? Ah! Another belief! My guess is it can exist, but not anytime soon. The only two good examples of software we have at this time are evolution and the brain, and they both are quite good, so why not be encouraged?

The beliefs I chose for this response are not fundamentally untestable. They might be tested someday, perhaps in a few centuries. It's not impossible that medical progress could keep me alive long enough to participate in testing them, so strictly speaking I can't guarantee that I can't ever prove these beliefs to be true.

There are not too many potential beliefs that could really never be tested by anyone ever. 

Consciousness, meaning, truth, and free will and their endless permutations just about complete the list. The reason philosophy is so much harder to talk about than science is that there's so little to talk about. It quickly becomes almost impossible to distinguish repetition from resonance.

Proposals like post-symbolic communication, however, frame questions about meaning that are small enough to be fresh and useful. Am I right that there can be meaning outside of words, or are the word-as-center-of-meaning folks correct?

Research Associate & Lecturer, Harvard; Adjunct Associate Professor, Brandeis; Author, Alex & Me
Research Scientist, MIT School of Architecture and Planning; Author, The Alex Studies

I believe, but can't prove, that human language evolved from a combination of gesture and innate vocalizations, via the concomitant evolution of mirror neurons, and that birds will provide the best model for language evolution.  

Work on mirror neurons over the past decade has provided intriguing evidence, although no solid proof, for the gestural origins of speech. What can be called the mirror neuron hypothesis(MNH) suggests that only a small re-organization of the nonhuman primate brain was needed to create the wiring that underlies speech acquisition/learning. What is missing from the MNH is a model of the development of language from speech; it is here that I believe that a model based on avian vocalizations is most valuable.

First, some background. Passerine birds can be divided into two groups: the oscines, who learn their songs, and the sub-oscines, who have a limited number of what seem to be innately-specified songs; the former have a well-defined neural architectures and mechanisms for song acquisition; the latter lack brain structures for song acquisition, although they obviously have brain and vocal tract structures for producing song. The sub-oscines, in parallel with nonhuman primates, often use various activities or gestures (posture, numbers of repetitions of songs, feather erectness, types of flights, etc) to provide additional information about the meaning of their utterances. W. John Smith, for example, can predict a flycatchers actions by the combination of posture, flight, and singing pattern he observes. The songbirds, like human children learning language, will not learn their vocalizations if deafened, and need to hear, babble and practice songs before attaining adult competence; very recent work by Rose et al. demonstrate that even the syntax of their song is learned through early exposure to paired phrases, which are then combined to create the adult vocalizations. Such data, demonstrating how sparrows integrate information about temporally-related events and how they use that information to develop sequential vocal behavior, is a viable model for human syntax acquisition.

Now, no one knows if any birds have any mirror neurons, and how their mirror neurons would function if they did exist; some neural data on responses to self-song provide intriguing hints but go no further. I predict (a) the existence of such neurons in oscines and (b) that such neurons will have a robust role in oscine song development, but (c) that only more primitively-functioning mirror neurons (akin to the differences separating monkey and human MNs) will be found in sub-oscines.

Now, what about the so-called missing link between learned and unlearned vocal behavior? No one has found such a missing link in the primate line. But Donald Kroodsma has recently discovered a flycatcher (a supposedly sub-oscine bird) that apparently learns its song. The song is simple, but has variations among groups of birds that constitute dialects. No one yet knows if these birds have brain mechanisms for song learning, or what these mechanisms might be. But I predict that Kroodsma's flycatchers will have mirror neurons that function in intermediate manner, between those of the oscines and sub-oscines, and will provide a model for the missing link between nonhuman primate and human communication.

Independent Investigator and Theoretician; Author, The Nurture Assumption; No Two Alike: Human Nature and Human Individuality
Writer and Developmental Psychologist; Author, The Nurture Assumption

I believe, though I cannot prove it, that three—not two—selection processes were involved in human evolution.

The first two are familiar: natural selection, which selects for fitness, and sexual selection, which selects for sexiness.

The third process selects for beauty, but not sexual beauty—not adult beauty. The ones doing the selecting weren't potential mates: they were parents. Parental selection, I call it.

What gave me the idea was a passage from a book titled Nisa: The Life and Words of a !Kung Woman, by the anthropologist Marjorie Shostak. Nisa was about fifty years old when she recounted to Shostak, in remarkable detail, the story of her life as a member of a hunter-gatherer group.

One of the incidents described by Nisa occurred when she was a child. She had a brother named Kumsa, about four years younger than herself. When Kumsa was around three, and still nursing, their mother realized she was pregnant again. She explained to Nisa that she was planning to "kill"—that is, abandon at birth—the new baby, so that Kumsa could continue to nurse. But when the baby was born, Nisa's mother had a change of heart. "I don't want to kill her," she told Nisa. "This little girl is too beautiful. See how lovely and fair her skin is?"

Standards of beauty differ in some respects among human societies; the !Kung are lighter-skinned than most Africans and perhaps they pride themselves on this feature. But Nisa's story provides a insight into two practices that used to be widespread and that I believe played an important role in human evolution: the abandonment of newborns that arrived at inopportune times (this practice has been documented in many human societies by anthropologists), and the use of aesthetic criteria to tip the scales in doubtful cases.

Coupled with sexual selection, parental selection could have produced certain kinds of evolutionary changes very quickly, even if the heartbreaking decision of whether to rear or abandon a newborn was made in only a small percentage of births. The characteristics that could be affected by parental selection would have to be apparent even in a newborn baby. Two such characteristics are skin color and hairiness.

Parental selection can help to explain how the Europeans, who are descended from Africans, developed white skin over such a short period of time. In Africa, a cultural preference for light skin (such as Nisa's mother expressed) would have been counteracted by other factors that made light skin impractical. But in less sunny Europe, light skin may actually have increased fitness, which means that all three selection processes might have worked together to produce the rapid change in skin color.

Parental selection coupled with sexual selection can also account for our hairlessness. In this case, I very much doubt that fitness played a role; other mammals of similar size—leopards, lions, zebras, gazelle, baboons, chimpanzees, and gorillas—get along fine with fur in Africa, where the change to hairlessness presumably took place. I believe (though I cannot prove it) that the transition to hairlessness took place quickly, over a short evolutionary time period, and involved only Homo sapiens or its immediate precursor.

It was a cultural thing. Our ancestors thought of themselves as "people" and thought of fur-bearing creatures as "animals," just as we do. A baby born too hairy would have been distinctly less appealing to its parents.

If I am right that the transition to hairlessness occurred very late in the sequence of evolutionary changes that led to us, then this can explain two of the mysteries of paleoanthropology: the survival of the Neanderthals in Ice Age Europe, and their disappearance about 30,000 years ago.

I believe, though I cannot prove it, that Neanderthals were covered with a heavy coat of fur, and that Homo erectus, their ancestor, was as hairy as the modern chimpanzee. A naked Neanderthal could never have made it through the Ice Age. Sure, he had fire, but a blazing hearth couldn't keep him from freezing when he was out on a hunt. Nor could a deerskin slung over his shoulders, and there is no evidence that Neanderthals could sew. They lived mostly on game, so they had to go out to hunt often, no matter how rotten the weather. And the game didn't hang around conveniently close to the entrance to their cozy cave.

The Neanderthals disappeared when Homo sapiens, who by then had learned the art of sewing, took over Europe and Asia. This new species, descended from a southern branch of Homo erectus, was unique among primates in being hairless. In their view, anything with fur on it could be classified as "animal"—or, to put it more bluntly, game. Neanderthal disappeared in Europe for the same reason the woolly mammoth disappeared there: the ancestors of the modern Europeans ate them. In Africa today, hungry humans eat the meat of chimpanzees and gorillas.

At present, I admit, there is insufficient evidence either to confirm or disconfirm these suppositions. However, evidence to support my belief in the furriness of Neanderthals may someday be found. Everything we currently know about this species comes from hard stuff like rocks and bones. But softer things, such as fur, can be preserved in glaciers, and the glaciers are melting. Someday a hiker may come across the well-preserved corpse of a furry Neanderthal.

Computer Scientist, Yale University; Chief Scientist, Mirror Worlds Technologies; Author, America-Lite: How Imperial Academia Dismantled our Culture (and ushered in the Obamacrats)
Computer Scientist, Yale University; Chief Scientist, Mirror Worlds Technologies; Author, Drawing Life

I believe (I know—but can't prove!) that scientists will soon understand the physiological basis of the "cognitive spectrum," from the bright violet of tightly-focused analytic thought all the way down to the long, slow red of low-focus sleep thought—also known as "dreaming." Once they understand the spectrum, they'll know how to treat insomnia, will understand analogy-discovery (and therefore creativity), and the role of emotion in thought—and will understand that thought takes place not only when you solve a math problem but when you look out the window and let your mind wander. Computer scientists will finally understand the missing mystery ingredient that made all their efforts to simulate human thought such naive, static failures, and turned this once-thriving research field into a ghost town. (Their failures were "static" insofar as people think in different ways at different times—your energetic, wide-awake mind works very differently from your tired, soon-to-be-sleeping mind; but artificial intelligence programs always "thought" in the same way all the time.)

And scientists will understand why we can't force ourselves to fall asleep orto "be creative"—and how those two facts are related. They'll understand why so many people report being most creative while driving, shaving or doing some other activity that keeps the mind's foreground occupied and lets it approach open problems in a "low focus" way. In short, they'll understand the mind as an integrated dynamic process that changes over a day and a lifetime, but is characterized always by one continuous spectrum.

Here's what we know about the cognitive spectrum: every human being traces out some version of the spectrum every day. You're most capable of analysis when you are most awake. As you grow less wide-awake, your thinking grows more concrete. As you start to fall asleep, you begin to free associate. (Cognitive psychologists have known for years that you begin to dream before you fall asleep.) We know also that to grow up intellectually means to trace out the cognitive spectrum in reverse: infants and children think concretely; as they grow up, they're increasingly capable of analysis. (Not incidentally, newborns spend nearly all their time asleep.)

Here's what we suspect about the cognitive spectrum: as you move down-spectrum, as your thinking grows less analytic and more concrete and finally bottoms on the wholly non-logical, highly concrete type of thought we call dreaming, emotions function increasingly as the "glue" of thought. I can't prove (but I believe) that "emotion coding" explains the problem of analogy. Scientists and philosophers have knocked their head against this particular brick wall for years: how can people say "a brick wall and a hard problem seem wholly different yet I can draw an analogy between them?" If we knew that, we'd understand the essence of creativity. The answer is: we are able to draw an analogy between two seemingly unlike things because the twoare associated in our minds with the same emotion. And that emotion acts as a connecting bridge between them. Each memory comes with a characteristic emotion; similar emotions allow us to connect two otherwise-unlike memories. An emotion (NB!) isn't the crude, simple thing we make it out to be in speaking or writing—"happy," "sad," etc.; an emotion can be the delicate, complex, nuanced, inexpressible feeling you get on the first warm day in spring.

And here's what we don't know: what's the physiological mechanism of the cognitive spectrum? What's the genetic basis? Within a generation, we'll have the answers.

Cosmologist; Physicist; Professor of Mathematical Science, Director, Millennium Mathematics Project, University of Cambridge; Author, The Book of Universes
Cosmologist, Cambridge University; Author, The Infinite Book

That our universe is infinite in size, finite in age, and just one among many. Not only can I not prove it but I believe that these statements will prove to be unprovable in principle and we will eventually hold that principle to be self-evident.

M.D. is Associate Professor of Neurology and Psychiatry at Albert Einstein College of Medicine and Chief of the Yarmon Neurobehavior and Alzheimer's Disease Center, Beth Israel Medical Center in New York City
Psychiatrist and Neurologist, Albert Einstein College of Medicine; Author, Altered Egos

I believe the human race will never decide that an advanced computer possesses consciousness. Only in science fiction will a person be charged with murder if they unplug a PC. I believe this because I hold, but cannot yet prove, that in order for an entity to be consciousness and possess a mind, it has to be a living being.

Being alive, of course, does not guarantee the presence of a mind. For example, a plant carries on the necessary metabolic functions to be alive, but still does not possess a mind. A chimpanzee, on the other hand, is a different story. All the behavioral features we share with chimps in addition to life, such as intelligence, the ability to deceive, mirror self-recognition, some individual social identity, make chimps seem so much like us that many in the scientific community intuitively grant chimps "beinghood" and consciousness. 

In addition to being alive, therefore, it appears that a living thing must be a being, must possess a self, to possess a mind. But silicon chips are not alive, and computers are not beings. I argue that this is so because the particular material substance and arrangement of the brain is essential to the creation of consciousness and "beinghood." Computers will never achieve consciousness because in order for a computer to be "conscious like us" it will need to be made of living stuff like us, to grow like us, and unfortunately, to be able to die like us. 

Science Fiction and Fantasy Writers of America
Novelist; Author, Globalhead

I can sum my intuition up in five words: we're in for climatic mayhem.

Science writings program at the Stevens Institute of Technology
Science Writer; Author, Rational Mysticism

I believe neuroscientists will never have enough understanding of the neural code, the secret language of the brain, to read peoples' thoughts without their consent.

The neural code is the software, algorithm, or set of rules whereby the brain transforms raw sensory data into perceptions, memories, decisions, meanings. A complete solution to the neural code could, in principle, allow scientists to monitor and manipulate minds with exquisite precision; you might, for example, probe the mind of a suspected terrorist for memories of past attacks or plans for future ones. The problem is, although all brains operate according to certain general principles, each person's neural code is to a certain extent idiosyncratic, shaped by his or her unique life history.

The neural pattern that underpins my concept of "George Bush" or "Heathrow Airport" or "surface-to-air missile" differs from yours. The only way to know how my brain encodes this kind of specific information would be to monitor its activity—ideally with thousands or even millions of implanted electrodes, which can detect the chatter of individual neurons—while I tell you as precisely as possible what I am thinking. But data you glean from studying me will be of no use for interpreting the signals of any other person. For ill or good, our minds will always remain hidden to some extent from Big Brother.

principal developer of the first omni-font optical character recognition
Inventor and Technologist; Author, The Age of Spiritual Machines

We will find ways to circumvent the speed of light as a limit on the communication of information.

We are expanding our computers and communication systems both inwardly and outwardly. Our chips use every smaller feature sizes, while at the same time we deploy greater amounts of matter and energy for computation and communication (for example, we're making a larger number of chips each year). In one to two decades, we will progress from two-dimensional chips to three-dimensional self-organizing circuits built out of molecules. Ultimately, we will approach the limits of matter and energy to support computation and communication. 

As we approach an asymptote in our ability to expand inwardly (that is, using finer features), computation will continue to expand outwardly, using readily available materials on Earth such as carbon. But we will eventually reach the limits of the resources available on our planet, and will expand outwardly to the rest of the solar system and beyond. 

So how quickly will we be able to do this? We could send tiny self-replicating robots at close to the speed of light along with electromagnetic transmissions containing the needed software. These nanobots could then colonize far-away planets. 

At this point, we run up against a seemingly intractable limit: the speed of light. Although a billion feet per second may seem fast, the Universe is spread out over such vast distances that this appears to represent a fundamental limit on how quickly an advanced civilization (such as we hope to become) can spread its influence. 

There are suggestions, however, that this limit is not as immutable as it may appear. Physicists Steve Lamoreaux and Justin Torgerson of the Los Alamos National Laboratory have analyzed data from an old natural nuclear reactor that two billion years ago produced a fission reaction lasting several hundred thousand years in what is now West Africa. Analyzing radioactive isotopes left over from the reactor and comparing them to isotopes from similar nuclear reactions today, they determined that the physics constant "alpha" (also called the fine structure constant), which determines the strength of the electromagnetic force apparently has changed since two billion years ago. The speed of light is inversely proportional to alpha, and both have been considered unchangeable constants. Alpha appears to have decreased by 4.5 parts out of 108. If confirmed, this would imply that the speed of light has increased. There are other studies with similar suggestions, and there is a table top experiment now under way at Cambridge University to test the ability to engineer a small change in the speed of light. 

Of course, these results will need to be carefully verified. If true, it may hold great importance for the future of our civilization. If the speed of light has increased, it has presumably done so not just because of the passage of time, but because certain conditions have changed. This is the type of scientific insight that technologists can exploit. It is the nature of engineering to take a natural, often subtle, scientific effect, and control it with a view towards greatly leveraging and magnifying it. If the speed of light has changed due to changing circumstances, that cracks open the door just enough for the capabilities of our future intelligence and technology to swing the door widely open. That is the nature of engineering. As one of many examples, consider how we have focused and amplified the subtle properties of Bernoulli's principle (that air rushing over a curved surface has a slightly lower air pressure than over a flat surface) to create the whole world of aviation. 

If it turns out that we are unable to actually change the speed of light, we may nonetheless circumvent it by using wormholes (which can be thought of as folds of the universe in dimensions beyond the three visible ones) as short cuts to far away places. 

In 1935, Einstein and physicist Nathan Rosen described "Einstein-Rosen" bridges as a way of describing electrons and other particles in terms of tiny space-time tunnels. In 1955, physicist John Wheeler described these tunnels as "wormholes," introducing the term for the first time. His analysis of wormholes showed them to be fully consistent with the theory of general relativity, which describes space as essentially curved in another dimension. 

In 1988, California Institute of Technology physicists Michael Morris, Kip Thorne, and Uri Yertsever described in some detail how such wormholes could be engineered. Based on quantum fluctuation, so-called "empty" space is continually generating tiny wormholes the size of subatomic particles. By adding energy and following other requirements of both quantum physics and general relativity (two fields that have been notoriously difficult to integrate), these wormholes could in theory be expanded in size to allow objects larger than subatomic particles to travel through them. Sending humans would not be impossible, but extremely difficult. However, as I pointed out above, we really only need to send nanobots plus information, which could go through wormholes measured in microns rather than meters. Anders Sandberg estimates that a one-nanometer wormhole could transmit a formidable 10^69 bits per second. 

Thorne and his Ph.D. students, Morris and Yertsever, also describe a method consistent with general relativity and quantum mechanics that could establish wormholes between Earth and far-away locations quickly even if the destination were many light-years away. 

Physicist David Hochberg and Vanderbilt University's Thomas Kephart point out that shortly after the Big Bang, gravity was strong enough to have provided the energy required to spontaneously create massive numbers of self-stabilizing wormholes. A significant portion of these wormholes are likely to still be around, and may be pervasive, providing a vast network of corridors that reach far and wide throughout the Universe. It might be easier to discover and use these natural wormholes than to create new ones. 

Would anyone be shocked if some subtle ways of getting around the speed of light were discovered? The point is that if there are even subtle ways around this limit, the technological powers that our future human-machine civilization will achieve will discover these means and leverage them to great effect. 

Software Pioneer; Philosopher; Author, "The History of the Future", "Frax—the first Realtime Fractals", "Chron—A Timeline of Literature"
Software: Concepts, Artwork & Interface Design; Byteburg Research Lab above the Rhein River

I always felt, but can't prove outright: Zen is wrong. Then is right. Everything is not about the now, as in the "here and how", "living for the moment" On the contrary: I believe everything is about the before then and the back then.

It is about the anticipation of the moment and the memory of the moment, but not the moment.

In German there is a beautiful little word for it: "Vorfreude", which still is a shade different from "delight" or "pleasure" or even "anticipation". It is the "Pre-Delight", the "Before-Joy", or as a little linguistic concoction: the "ForeFun"; in a single word trying to express the relationship of time, the pleasure of waiting for the moment to arrive, the can't wait moments of elation, of hoping for some thing, some one, some event to happen.

Whether it's on a small scale like that special taste of your favorite food, waiting to see a loved one, that one moment in a piece of music, a sequence in a movie....or the larger versions: the expectation of a beautiful vacation, the birth of a baby, your acceptance of an Oscar.

We have been told by wise men, Dalais and Maharishis that it is supposedly all about those moments, to cherish the second it happens and never mind the continuance of time...

But for me, since early childhood days, I realized somehow: the beauty lies in the time before, the hope for, the waiting for, the imaginary picture painted in perfection of that instant in time. And then, once it passes, in the blink of an eye, it will be the memory which really stays with you, the reflection, the remembrance of that time. Cherish the thought..., remember how....

Nothing ever is as beautiful as its abstraction through the rose-colored glasses of anticipation...The toddlers hope for Santa Claus on Christmas eve turns out to be a fat guy with a fashion issue. Waiting for the first kiss can give you waves of emotional shivers up your spine, but when it then actually happens, it's a bunch of molecules colliding, a bit of a mess, really.  It is not the real moment that matters. In Anticipation the moment will be glorified by innocence, not knowing yet. In Remembrance the moment will be sanctified by memory filters, not knowing any more.

In the Zen version, trying to uphold the beauty of the moment in that moment is in my eyes a sad undertaking. Not so much because it can be done, all manner of techniques have been put forth how to be a happy human by mastering the art of it.  But it also implies, by definition, that all those other moments live just as much under the spotlight: the mundane, the lame, the gross, the everyday routines of dealing with life's mere mechanics.

In the Then version, it is quite the opposite: the long phases before and after last hundreds or thousands of times longer than the moment, and drown out the everyday humdrum entirely.

Bluntly put: spend your life in the eternal bliss of always having something to hope for, something to wait for, plans not realized, dreams not come true.... Make sure you have new points on the horizon, that you purposely create. And at the same time, relive your memories, uphold and cherish them, keep them alive and share them, talk about them.

Make plans and take pictures.

I have no way of proving such a lofty philosophical theory, but I greatly anticipate the moment that I might... and once I have done it, I will, most certainly, never forget.

Founding member of Xerox PARC; President of Viewpoints Research Institute, Inc
Computer Scientist; Personal Computer Visionary, Senior Fellow, HP Labs

Einstein said "You must learn to distinguish between what is true and what is real". An apt longer quote of his is: "As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality". I.e. it is "true" that the three angles of a triangle add up to 180 in Euclidean geometry of the plane, but it is not known how to show that this could hold in our physical universe (if there is any mass or energy in our universe then it doesn't seem to hold, and it is not actually known what our universe would be like without any mass or energy).

So, science is a relationship between what we can represent and are able to think about, and "what's out there": it's an extension of good map making, most often using various forms of mathematics as the mapping languages. When we guess in science we are guessing about approximations and mappings to languages, we are not guessing about "the truth" (and we are not in a good state of mind for doing science if we think we are guessing "the truth" or "finding the truth"). This is not at all well understood outside of science, and there are unfortunately a few people with degrees in science who don't seem to understand it either.

Sometimes in math one can guess a theorem that can be proved true. This is a useful process even if one's batting average is less than .500. Guessing in science is done all the time, and the difference between what is real and what is true is not a big factor in the guessing stage, but makes all the difference epistemologically later in the process.

One corner of computing is a kind of mathematics (other corners include design, engineering, etc.). But there are very few interesting actual proofs in computing. A good Don Knuth quote is: "Beware of bugs in the above code; I have only proved it correct, not tried it."

An analogy for why this is so is to the n-body problems (and other chaotic systems behaviors) in physics. An explosion of degrees of freedom (3 bodies and gravity is enough) make a perfectly deterministic model impossible to solve analytically for a future state. However, we can compute any future state by brute force simulation and see what happens. By analogy, we'd like to prove useful programs correct, but we either have intractable degrees of freedom, or as in the Knuth quote, it is very difficult to know if we've actually gathered all the cases when we do a "proof".

So a guess in computing is often architectural or a collection of "covering heuristics". An example of the latter is TCP/IP which has allowed "the world's largest and most scalable artifact—The Internet—to be successfully built. An example of the former is the guess I made in 1966 about objects—not that one could build everything from objects—that could be proved mathematically—but that using objects would be a much better way to represent most things. This is not very provable, but like the Internet, now has quite a body of evidence that suggests this was a good guess.

Another guess I made long ago—that does not yet have a body of evidence to support it—is that what is special about the computer is analogous to and an advance on what was special about writing and then printing. It's not about automating past forms that has the big impact, but as McLuhan pointed out, when you are able to change the nature of representation and argumentation, those who learn these new ways will wind up to be qualtitatively different and better thinkers, and this will (usually) help advance our limited conceptions of civilization.

This still seems like a good guess to me—but "truth" has nothing to do with it.

researcher in the evolution of human intelligence in the light of recent discoveries about the brain
Neuroscience researcher; Coauthor, Up From Dragons

Here's what I believe but cannot prove: human beings, like all animals, have evolved a range of capacities for fighting disease and recovering from injury, including a variety of 'sickness behaviors'; humans beings alone however have discovered the advantages of off-loading much of the responsibility for managing their sickness behaviors to other people; the result is that for human beings the very nature of illness has changed—human illness is now largely a social phenomenon.

This is possible because "illness" is a response. A rise in body temperature, for example, kills many bacteria and changes the membrane properties of cells so viruses cannot replicate. The pain of a broken bone or weak heart makes sure we let it heal or rest. Nature supplied our bodies in this way with a first-aid kit but unfortunately like many medicines their "treatments" are unpleasant. That unpleasantness, not the dysfunction which they seek to remedy is what we call "illness".

These remedies, however, have costs as well as benefits making it often difficult for the body to know whether to deploy them. A fever might fight an infection but if the body lacks sufficient energy stores, the fever might kill. The body therefore must make a decision whether the gain of clearing the infection merits the risk. Complicating that decision is that the body is blind, for example, to whether it faces a mild or a life-threatening virus. The body thus deploys its treatments in a precautionary manner. If only one in ten fevers actually clears an infection that would kill, it makes sense to tolerate the cost of the other nine. Most of the body's capacities for fighting disease and repairing injury are deployed in this precautionary way. We feel pain in a broken limb so we treat it over protectively—in nine occasions out of ten we could get by with less protective pain but on the tenth it stops us causing it further injury. But precautionary deployment is costly. Evolution therefore has put the evaluation of such deployment under the control of the brain in attempt to keep their use to a minimum.

But the brain on its own often lacks the experience to know our own condition. Fortunately, other people can, particularly those that have studied health and illness.

Human evolution therefore changed illness by offloading decisions about deployment whenever possible on to professionals. People that make themselves experienced in disease and injury, after all, have the background knowledge to know our bodies much better than ourselves. Healing professionals—healers, shamans, witch doctors and medics—exist in all human cultures. Of course, such professionals were seen by their patients as offering real treatments—and a few did help such as advising rest, eating well and some medicinal herbs. But most of what they did was ineffective. Doctors indeed had to wait until 1908 and Paul Ehrlich's discovery of Salvarsan for treating syphilis before they had a really effective treatment for a major disease. Nonetheless earlier doctors and healers were considered by themselves and their patients to be in the possession of very powerful cures.

Why? The answer I believe was that their ineffective rituals and potions actually worked. Evolution prepared us to offload control of our abilities to fight disease and heal injuries to those that knew more than us. The rituals and quackery of healers might have not worked but they certainly made a patient feel they were in the hands of an expert. That gave a healer great power over their patient. As noted, many of the body's own "treatments" are used on a precautionary basis so they can be stopped without harm. A healer could do this by applying an impressive "cure" that persuaded the body that its own "treatments" were no longer needed. The body would trust its healer and halt its own efforts and so the "illness". The patient as a result would feel much better, if not cured. Human evolution therefore made doctoring more than just a science and a question of prescribing the right treatment. It made it also an art by which a doctor persuades the patient's body to offload its decision making onto them.

Professor of Biological Sciences, Physics, Astronomy, University of Calgary; Author, Reinventing the Sacred
Biologist, Santa Fe Institute; Author, Investigations

Is there a fourth law of thermodynamics, or some cousin of it, concerning self constructing non equilibrium systems such as biospheres anywhere in the cosmos?

I like to think there may be such a law.

Consider this, the number of possible proteins 200 amino acids long is 20 raised to the 200th power or about 10 raised to the 260th power. Now, the number of particles in the known universe is about 10 to the 80th power. Suppose, on a microsecond time scale the universe were doing nothing other than producing proteins length 200. It turns out that it would take vastly many repeats of the history of the universe to create all possible proteins length 200. This means that, for entities of complexity above atoms, such as modestly complex organic molecules, proteins, let alone species, automobiles and operas, the universe is on a unique trajectory (ignoring quantum mechanics for the moment). That is, the universe at modest levels of complexity and above is vastly non-ergodic.

Now conceive of the "adjacent possible", the set of entities that are one "step" away from what exists now. For chemical reaction systems, the adjacent possible from a set of compounds already existing (called the "actual" ) is just the set of novel compounds that can be produced by single chemical reactions among the initial "actual" set. Now, the biosphere has expanded into its molecular adjacent possible since 4.8 billion years ago.

Before life, there were perhaps a few hundred organic molecule species on the earth. Now there are perhaps a trillion or more. We have no law governing this expansion into the adjacent possible in this non-ergodic process. My hoped for law is that biospheres everywhere in the universe expand in such a way that they do so as fast as is possible while maintaining the rough diversity of what already exists. Otherwise stated, the diversity of things that can happen next increases on average as fast as it can.

Professor of Psychology and Co-Director of the Mind, Brain, and Behavior Initiative
Psychologist, Harvard University

I believe, first, that all people have the same fundamental concepts, values, concerns, and commitments, despite our diverse languages, religions, social practices, and expressed beliefs. If defenders and opponents of abortion, Israelis and Palestinians, or Cambridge intellectuals and Amazonian jungle dwellers were to get beyond their surface differences, each would discover that the common ground linking them to members of the other group equals that which binds their own group together. Our common conceptual and moral commitments spring from the core cognitive systems that allow an infant to grow rapidly and spontaneously into a competent participant in any human society.

Second, one of our shared core systems centers on a notion that is false: the notion that members of different human groups differ profoundly in their concepts and values. This notion leads us to interpret the superficial differences between people as signs of deeper differences. It has quite a grip on us: Many people would lay down their lives for perfect strangers from their own community, while looking with suspicion at members of other communities. And all of us are apt to feel a special pull toward those who speak our language and share our ethnic background or religion, relative to those who don't.

Third, the most striking feature of human cognition stems not from our core knowledge systems but from our capacity to rise above them. Humans are capable of discovering that our core conceptions are false, and of replacing them with truer ones. This change has happened dramatically in the domain of astronomy. Core capacities to perceive, act on, and reason about the surface layout predispose us to believe that the earth is a flat, extended surface on which gravity acts as a downward force. This belief has been decisively overturned, however, by the progress of science. Today, every child who plays computer games or watches Star Wars knows that the earth is one sphere among many, and that gravity pulls all these bodies toward one another.

Together, my three beliefs suggest a fourth. If the cognitive sciences are given sufficient time, the truth of the claim of a common human nature eventually will be supported by evidence as strong and convincing as the evidence that the earth is round. As humans are bathed in this evidence, we will overcome our misconceptions of human differences. Ethnic and religious rivalries and conflicts will come to seem as pointless as debates over the turtles that our pancake earth sits upon, and our common need for a stable, sustainable environment for all people will be recognized. But this fourth belief is conditional. Our species is caught in a race between the progress of our science and the escalation both of our intergroup conflicts and of the destructive means to pursue them. Will humans last long enough for our science to win this race?

Theoretical Philosopher, Johannes Gutenberg-Universität Mainz; Author, The Ego Tunnel
Johannes Gutenberg-Universität Mainz; Author, Being No One

I believe, but cannot prove, that a First Breakthrough on Consciousness is actually around the corner. "Actually around the corner" means: less than 50 years away. My intuition is that, roughly, all we need for this first breakthrough are four convincing stories.

The first story will be about global integration, about the dynamical self-organization of long-range binding operations in the human brain. It will probably involve something like synchrony in multiple frequency bands, and will let us understand how a unified model of the world can emerge in our own heads.

The second story will be about "transparency": Why is it that we are unable to consciously experience most of the images our brain generates as images? The answer to this question will give us a real world. The transparency-tale has to do with not being able to see earlier processing stages and becoming a naive realist.

The third story will focus on the Now, the emergence of a psychological moment—on a deeper understanding of what William James' called the "specious present". Experts on short term memory and neural network modelers with tell this story for us. As it unfolds, it will explain the emergence of a subjective present and let us understand how conscious experience, in its simplest and most essential form, is the presence of a world.

Interestingly, today almost everybody in the consciousness community already agrees on some version of the fourth story: Consciousness is directly linked to attentional processing, more precisely, to a hidden mechanism constantly holding information available for attention. The subjective presence of a world is a clever strategy of making integrated informationavailable for attention.

I believe, but cannot prove, that this will allow us to find the global neural correlate for consciousness. However, being a philosopher, I want much more than that—I am also interested in precise concepts. What I will be waiting for is the young mathematician who then comes along and suddenly allows us to see how all of these four stories were actually only one: The genius who gives us a formal model describing the information flow in this neural correlate, and in just the right way. She will harvest the fruits of generations or researchers before her, and this will be the First Breakthrough on Consciousness.

Then three things will happen.

1. The Second Breakthrough on Consciousness will take much longer. Things will get messy and complicated. The philosophy and neuroscience of consciousness will get bogged down in diabolic details and ugly technical problems. Public attention will soon shift away from the problem of consciousness per se. Instead, new generations of young researchers will now focus on the nature of self and social cognition.

2. The overall development will have an unexpectedly strong cultural impact. People will not want to face their own mortality. There will be fundamentalist and anti-rational counter movements against the scientific image of man. At the same time crude new ideologies propagating vulgar forms of materialism and primitive forms of hedonism will spring up. Scientists will realize that one can not reductively explain the human mind and then simply look another way, leaving the consequences for someone else to deal with.

3. We will be able to influence consciousness in ways we have never dreamt of. There will be a new form of technology—Consciousness Technology—exclusively focusing on how to manipulate the neural correlate of consciousness in ever more fine-grained, efficient, and risk-free ways. People will realize that we need some sort of applied ethics for this new type of technology. And hopefully we will all together start to tell a newstory—a story about how to live with these brains and about what a good state of consciousness actually is.

Cognitive Scientist; Author, Guitar Zero: The New Musician and the Science of Learning
Psychologist, New York University; Author, The Birth of the Mind

If computers are made up of hardware and software, transistors and resistors, what are neural machines we know as minds made up of?

Minds clearly are not made up of transistors and resistors, but I firmly believe that at least one of the most basic elements of computation is shared by man and machine: the ability to represent information in terms of an abstract, algebra-like code.

In a computer, this means that software is made up of hundreds, thousands, even millions of lines that say things like IF X IS GREATER THAN Y, DO Z, orCALCULATE THE VALUE OF Q BY ADDING A, B, AND C. The same kind of abstraction seems to underlie our knowledge of linguistics. For instance, the famous linguistic dictum that a Sentence consists of a Noun Phrase plus a Verb Phrase can apply to an infinite number of possible nouns and verbs, not just a few familiar words. In its open-endedness, it is an example of mental algebra par excellence.

In my lab, we discovered that even infants seem to be able to grasp something quite similar. For example, in the course of just two minutes, a seven-month-old baby can extract the ABA "grammar" inherent in set of made-up sentences like la ta la, ga na ga, je li je. Or the ABB "grammar" in sentences like la ta ta, ga na na, je li li.

Of course, this experiment doesn't prove that there is an "algebra" circuit in the brain—psychological techniques alone can't do that. For final proof, we'll need neuroscientific techniques far more sophisticated than contemporary brain imaging, such that we can image the brain at the level of interactions between individual neurons. But every bit of evidence that we can collect now—from babies, from toddlers, from adults, from psychology and from linguistics—seems to confirm the idea that algebra-like abstraction is a fundamental component of thought.

Neuroscientist; Chairman, Project Reason; Author, Waking Up
Neuroscience Researcher; Author, The End of Faith

Twenty-two percent of Americans claim to be certain that Jesus will return to earth to judge the living and the dead sometime in the next fifty years. Another twenty-two percent believe that he is likely to do so. The problem that most interests me at this point, both scientifically and socially, is the problem of belief itself. What does it mean, at the level of the brain, to believe that a proposition is true? The difference between believing and disbelieving a statement—Your spouse is cheating on you; you've just won ten million dollars—is one of the most potent regulators of human behavior and emotion. The instant we accept a given representation of the world as true, it becomes the basis for further thought and action; rejected as false, it remains a string of words.

What I believe, though cannot yet prove, is that belief is a content-independent process. Which is to say that beliefs about God—to the degree that they are really believed—are the same as beliefs about numbers, penguins, tofu, or anything else. This is not to say that all of our representations of the world are acquired through language, or that all linguistic representations are on the same logical footing. And we know that different regions of the brain are involved in judging the truth-value of statements drawn from different content domains. What I do believe, however, is that the neural processes that govern the final acceptance of a statement as "true" rely on more fundamental, reward-related circuitry in our frontal lobes—probably the same regions that judge the pleasantness of tastes and odors. Truth may be beauty, and beauty truth, in more than a metaphorical sense. And false statements may, quite literally, disgust us.

Once the neurology of belief becomes clear, and it stands revealed as an all-purpose emotion arising in a wide variety of contexts (often without warrant), religious faith will be exposed for what it is: a humble species of terrestrial credulity. We will then have additional, scientific reasons to declare that mere feelings of conviction are not enough when it comes time to talk about the way the world is. The only thing that guarantees that (sufficiently complex) beliefs actually represent the world, are chains of evidence and argument linking them to the world. Only on matters of religious faith do sane men and women regularly dispute this fact. Apart from removing the principle reason we have found to kill one another, a revolution in our thinking about religious belief would clear the way for new approaches to ethics and spiritual experience. Both ethics and spirituality lie at the very heart of what is good about being human, but our thinking on both fronts has been shackled to the preposterous for millennia. Understanding belief at the level of the brain may hold the key to new insights into the nature of our minds, to new rules of discourse, and to new frontiers of human cooperation.

Managing Director of CyberLab Interactive Productions GmbH
Economist; Managing Director of CyberLab Interactive Productions GmbH (Burda Media Group).

When considering this question one has to remember the basis of the scientific method: formulating hypotheses that can be disproved. Those hypotheses that are not disproved are thought to be true until disproved. Since it is more glamorous for a scientist to formulate hypotheses that it is to spend years disproving existing ones from other scientists and that it is unlikely that someone will spend enough time and energy trying to disprove his/her own statements, our body of scientific knowledge is surely full of statements we believe to be true but will eventually be proved to be false.

So I turn the question around: What scientific ideas that have not been disproved, do you believe are false.

In my field (theoretical economics), I believe that most ideas taught in economics 101 will be proved false eventually. Most of them would already have been officially defined as false in any other more hard-science, but, because of lack of better hypotheses they are still widely accepted and used in economics and general commentary. Eventually, someone will come up with another type of hypotheses explaining (and predicting) the economic reality in a way that will render most existing economics beliefs false.

Writer and Television Producer; Author, Remembering Our Childhood: How Memory Betrays Us
Writer and Television Producer; Author, The Riemann Hypothesis

I believe it is true that if there is intelligent life elsewhere in the universe, of whatever form, it will be familiar with the same concept of counting numbers.

Some philosophers believe that pure mathematics is human-specific and that it is possible for an entirely different type of mathematics to emerge from a different type of intelligence, a type of mathematics that has nothing in common with ours and may even contradict it. But it is difficult to think of what sort of life-form would not need the counting numbers. The stars in the sky are discrete points and cry out to be counted by beings throughout the universe, but alien life-forms may not have vision. 

Intelligent objects with boundaries between being and non-being surely want to be measured— "I'm bigger that you", "I need a size 312 overcoat"—but perhaps there are life-forms which don't have boundaries but are continuously varying density changes in some Jovian sea. Intelligent life might be disembodied or at least lack a discrete body and merely be transmitted between various points in a solid material matrix, so that it was impossible to distinguish one intelligent being from another.

But sooner or later, whether it is to measure the passing of time, the magnitude of distance, the density of one Jovian being compared with another, numbers will have to be used. And if numbers are used, 2 + 2 must always equal 4, the number of stars in the Pleiades brighter than magnitude 5.7 will always be 11 which will always be a prime number, and two measurements of the speed of light in any units in identical conditions will always be identical. Of course, the fact that I find it difficult to think of beings which won't need our sort of mathematics doesn't mean they don't exist, but that's what I believe without proof.

Biologist, Distinguished University Professor, UMass, Amherst; Coauthor (with Dorion Sagan), Acquiring Genomes: A Theory of the Origins of Species
Biologist, University of Massachusetts, Amherst; Author, Symbiosis in Cell Evolution.

I feel that I know something that will turn out to be correct and eventually proved to be true beyond doubt 

What?

That our ability to perceive signals in the environment evolved directly from our bacterial ancestors. That is, we, like all other mammals including our apish brothers detect odors, distinguish tastes, hear bird song and drum beats and we too feel the vibrations of the drums. With our eyes closed we detect the light of the rising sun. These abilities to sense our surroundings are a heritage that preceded the evolution of all primates, all vertebrate animals, indeed all animals. Such sensitivities to wafting plant scents, tasty salted mixtures, police cruiser sirens, loving touches and star light register because of our "sensory cells".

These avant guard cells of the nasal passages, the taste buds, the inner ear, the touch receptors in the skin and the retinal rods and cones all have in common the presence at their tips of projections ("cell processes") called cilia. Cilia have a recognizable fine structure. With a very high power ("electron") microscope a precise array of protein tubules, nine, exactly nine pairs of tubules are arranged in a circular array and two singlet tubules are in the center of this array. All sensory cells have this common feature whether in the light-sensitive retina of the eye or the balance-sensitive semicircular canals of the inner ear. Cross-section slices of the tails of human, mouse and even insect (fruit-fly) sperm all share this same instantly recognizable structure too. Why this peculiar pattern? No one knows for sure but it provides the evolutionist with a strong argument for common ancestry. The size (diameter) of the circle (0.25 micrometers) and of the constituent tubules (0.024 micrometers) aligned in the circle is identical in the touch receptors of the human finger and the taste buds of the elephant.

What do I feel that I know, what Oscar Wilde said (that "even true things can be proved")?

Not only that the sensory cilia derive from these exact 9-fold symmetrical structures in protists such as the "waving feet" of the paramecium or the tail of the vaginal-itch protist called Trichomonas vaginalis. Indeed, all biologists agree with the claim that sperm tails and all these forms of sensory cilia share a common ancestry.

But I go much farther. I think the the common ancestor of the cilium, but not the rest of the cell, was a free-swimming entity, a skinny snake-like bacterium that, 1500 million years ago squiggled through muds in a frantic search for food. Attracted by some smells and repelled by others the bacteria, by themselves, already enjoyed a repertoire of sensory abilities that remain with their descendants to this day. In fact, this bacterial ancestor of the cilium never went extinct, rather some of its descendants are uncomfortably close to us today. This hypothetical bacterium, ancestor to all the cilia, was no ordinary rod-shaped little dot.

No, this bacterium who still has many live relatives, entered into symbiotic partnerships with other very different kinds of bacteria. Together this two component partnership swam and stuck together both persisted. What kind of bacterium became an attached symbiont that impelled its partner forward? None other than a squirming spirochete bacterium.

The spirochete group of bacteria includes many harmless mud-dwellers but it also contains a few scary freaks: the treponeme of syphilis and the borrelias of Lyme disease. We animals got our exquisite ability to sense our surroundings—to tell light from dark, noise from silence, motion from stillness and fresh water from brackish brine—from a kind of bacterium whose relatives we despise. Cilia were once free-agents but they became an integral part of all animal cells. Even though the concept that cilia evolved from spirochetes has not been proved I think it is true. Not only is it true but, given the powerful new techniques of molecular biology I think the hypothesis will be conclusively proved. In the not-too-distant future people will wonder why so many scientists were so against my idea for so long!

Evolutionary Biologist; Emeritus Professor of the Public Understanding of Science, Oxford; Author, The Greatest Show on Earth, The Magic of Reality

I believe that all life, all intelligence, all creativity and all 'design' anywhere in the universe, is the direct or indirect product of Darwinian natural selection. It follows that design comes late in the universe, after a period of Darwinian evolution. Design cannot precede evolution and therefore cannot underlie the universe

Anthropologist, National Center for Scientific Research, Paris; Author, Talking to the Enemy
Anthropologist, University of Michigan; Author, In God's We Trust

There is no God that has existence apart from people's thoughts of God. There is certainly no Being that can simply suspend the (nomological) laws of the universe in order to satisfy our personal or collective yearnings and whims—like a stage director called on to change and improve a play. But there is a mental (cognitive and emotional) process common to science and religion of suspending belief in what you see and take for obvious fact. Humans have a mental compulsion—perhaps a by-product of the evolution of a hyper-sensitive reasoning device to serve our passions—to situate and understand the present state of mundane affairs within an indefinitely extendable and overarching system of relations between hitherto unconnected elements. In any event, what drives humanity forward in history is this quest for non-apparent truth.

Emeritus Professor of Physics and Astronomy, UC-Irvine; Novelist, Shipstar
Physicist, UC Irvine; Author, Deep Time

Why is there scientific law at all?

We physicists explain the origin and structure of matter and energy, but not the laws that do this. Does the idea of causation apply to where the laws themselves came from? Even Alan Guth's "free lunch" gives us the universe after the laws start acting. We have narrowed down the range of field theories that can yield the big bang universe we live in, but why do the laws that govern it seem to be constant in time, and always at work?

One can imagine a universe in which laws are not truly lawful. Talk of miracles does just this, when God is supposed to make things work. Physics aims to find The Laws and hopes that these will be uniquely constrained, as when Einstein wondered if God had any choice when He made the universe. One fashionable escape hatch from this asserts that there are infinitely many universes, each sealed off from the others, which can obey any sort of law one can imagine, with parameters or assumptions changed. This "multiverse" view represents the failure of our grand agenda, of course, and seems to me contrary to Occam's Razor—solving our lack of understanding by multiplying unseen entities into infinity.

Perhaps it is a similar philosophical failure of imagination to think, as I do, that when we see order, there is usually an ordering principle. But what can constrain the nature of physical law? Evolution gave us our ornately structured biosphere, and perhaps a similar principle operates in selecting universes. Perhaps our universe arises, then, from selection for intelligences that can make fresh universes, perhaps in high energy physics experiments. Or near black holes (as Lee Smiolin supposed), where space-time gets contorted into plastic forms that can make new space-times. Then an Ur-universe that had intelligence could make others, and this reproduction with perhaps slight variation ion "genetics" drives the evolution of physical law.

Selection arises because only firm laws can yield constant, benign conditions to form new life. Ed Harrison had similar ideas. Once life forms realize this, they could intentionally make more smart universes with the right, fixed laws, to produce ever more grand structures. There might be observable consequences of this prior evolution, If so, then we are an inevitable consequence of the universe, mirroring intelligences that have come before, in some earlier universe that deliberately chose to create more sustainable order. The fitness of our cosmic environment is then no accident. If we find evidence of fine-tuning in the Dyson and Rees sense, then, is this evidence for such views?

Professor of Computer Science, MIT; Director, Human Dynamics Lab and the Media Lab Entrepreneurship Program; Author, Social Physics
Computer Scientist, MIT Media Laboratory

Tribal Mind.

What would it be like to be part of a distributed intelligence but still with an individual consciousness? Well for starters, you might expect to see the collective mind 'take over' from time to time, directly guiding the individual minds. In humans, the behavior of angry mobs and frightened crowds seem to qualify as examples of a 'collective mind' in action, with non-linguistic channels of communication usurping the individual capacity for rational behavior.

But as powerful as this sort of group compulsion can be, it is usually regarded as simply a failure of individual rationality, a primitive behavioral safety net for the tribe in times of great stress. Surely this tribal mind doesn't operate in normal day-to-day behavior—or does it? If we imagined that human behavior was in substantial part due to a collective tribal mind, you would expect that non-linguistic social signaling—the type that drives mob behavior—would be predictive of even the most rational and important human interactions. Analogous with the wiggle dance of the honeybee, there ought to be non-linguistic signals that accurately predict important behavioral outcomes.

And that is exactly what I find. Together with my research group I have built a computer system that objectively measures a set of non-linguistic social signals, such as engagement, mirroring, activity, and stress, by looking at 'tone of voice' over one minute time periods. Although people are largely unconscious of this type of behavior, other researchers (Jaffe, Chartrand and Bargh, France, Kagen) have shown that similar measurements are predictive of infant language development, judgments of empathy, depression, and even personality development in children. Working with colleagues, we have found that we can use these measurements of social signaling to automatically predict a wide range of important behavioral outcomes—objective, instrumental, and subjective—with high accuracy, accounting for between 30% and 80% of the total outcome variance.

Examples of objective and instrumental behaviors where we can accurately predict the outcome include salary negotiations, dating decisions, and role in the social network. Examples of subjective predictions include hiring preferences, empathy perceptions, and interest ratings. Even for lengthy interactions, accurate predictions can be made by observing only the initial few minutes of interaction, even though the linguistic content of these 'thin slices' of the behavior seem to have little predictive power.

I find all of this astounding. We are examining some of the most important interactions a human has: finding a mate, getting a job, negotiating a salary, finding your place in your social network. These are activities for which we prepare intellectually and strategically for decades. And yet the largely unconscious social signaling that occurs at the start of the interaction appears to be more predictive than either the contextual facts (is he attractive? is she experienced?) or the linguistic structure (e.g., strategy chosen, arguments employed, etc.).

So what is going on here? One might speculate that the social signaling we are measuring evolved as a method of establishing tribal hierarchy and cohesion, analogous to Dunbar's view that language evolved as grooming behavior. On this view the tribal mind would function as unconscious collective discussion about relationships and resources, risks and rewards, and would interact with the conscious individual minds by filtering ideas by their value relative to the tribe. Our measurements tap into the discussion, and predict outcome by use of social regularities. For instance, in a salary negotiation it is important for the lower-status individual to establish that they are 'team player' by being empathetic, while in a potential dating situation the key variable is the female's level of interest. In our data there seem to be patterns of signaling that reliably lead to these desired states.

One question to ask about this social signaling is whether or not it is an independent channel of communication, e.g., is it causal or do the signals arise from the linguistic structure? We don't have the full answer to that yet, but we do know that similar measurements predict infant language and personality development, that adults can change their signaling by adopting different roles or identities within a conversation, and in our studies the linguistic and factual content seems uncorrelated with the pattern or intensity of social signaling. So even if social signaling turns out to be only an adjunct to normal linguistic structure, it is a very interesting addition: it is a little like having speech annotated with speaker intent!

So here is what I suspect but can not prove: a very large proportion of our behavior is determined by largely unconscious social signaling, which sets the context, risk, and reward structure within which traditional cognitive processes proceed. This conjecture resonates with Pinker's view about brain complexity, and with Kosslyn's thoughts about social prosthetic systems. It is also provides a concrete mechanism for the well-known processes of group polarization ('the risky shift'), groupthink, and the sometimes irrational behaviors of larger groups. In short, it may be useful to starting thinking of humans as having a collective, tribal mind in addition to their personal mind.

Psychologist, Director, Institute of Cognition and Culture, Queens University, Belfast; Columnist, Scientific American; Author, Perv
Psychologist, University of Arkansas

In 1936, shortly after the outbreak of the Spanish Civil War, the moribund philosopher Miguel de Unamuno, author of the classic existential text Tragic Sense of Life, died alone in his office of heart failure at the age of 72.

Unamuno was no religious sentimentalist. As a rector and Professor of Greek at the University of Salamanca, he was an advocate of rationalist ideals and even died a folk hero for openly denouncing Francisco Franco's fascist regime. He was, however, ridden with a 'spiritual' burden that troubled him nearly all his life. It was the problem of death. Specifically, the problem was his own death, and what, subjectively, it would be "like" for him after his own death: "The effort to comprehend it causes the most tormenting dizziness." I've taken to calling this dilemma "Unamuno's paradox" because I believe that it is a universal problem. It is, quite simply, the materialist understanding that consciousness is snuffed out by death coming into conflict with the human inability to simulate the psychological state of death.

Of course, adopting a parsimonious stance allows one to easily deduce that we as corpses cannot experience mental states, but this theoretical proposition can only be justified by a working scientific knowledge (i.e., that the non-functioning brain is directly equivalent to the cessation of the mind). By stating that psychological states survive death, or even alluding to this possibility, one is committing oneself to a radical form of mind-body dualism. Consider how bizarre it truly is: Death is seen as a transitional event that unbuckles the body from its ephemeral soul, the soul being the conscious personality of the decedent and the once animating force of the now inert physical form. This dualistic view sees the self as being initially contained in bodily mass, as motivating overt action during this occupancy, and as exiting or taking leave of the body at some point after its biological expiration. So what, exactly, does the brain do if mental activities can exist independently of the brain? After all, as John Dewey put it, mind is a verb, not a noun.

And yet this radicalism is especially common. In the United States alone, as much as 95% of the population reportedly believes in life after death. How can so many people be wrong? Quite easily, if you consider that we're all operating with the same standard, blemished psychological hardware. It's tempting to argue, as Freud did, that it's just people's desire for an afterlife that's behind it all. But it would be a mistake to leave it at that. Although there is convincing evidence showing that emotive factors can be powerful contributors to people's belief in life after death, whatever one's motivations for rejecting or endorsing the idea of an immaterial soul that can defy physical death, the ability to form any opinion on the matter would be absent if not for our species' expertise at differentiating unobservable minds from observable bodies.

But here's the rub. The materialist version of death is the ultimate killjoy null hypothesis. The epistemological problem of knowing what it is "like" to be dead can never be resolved. Nevertheless, I think that Unamuno would be proud of recent scientific attempts to address the mechanics of his paradox. In a recent study, for example, I reported that when adult participants were asked to reason about the psychological abilities of a protagonist who had just died in an automobile accident, even participants who later classified themselves as "extinctivists" (i.e., those who endorsed the statement "what we think of as the 'soul,' or conscious personality of a person, ceases permanently when the body dies") nevertheless stated that the dead person knew that he was dead. For example, when asked whether the dead protagonist knew that he was dead (a feat demanding, of course, ongoing cognitive abilities), one young extinctivist's answer was almost comical. "Yeah, he'd know, because I don't believe in the afterlife. It is non-existent; he sees that now." Try hard as he might to be a good materialist, this subject couldn't help but be a dualist.

How do I explain these findings? Like reasoning about one's past mental states during dreamless sleep or while in other somnambulistic states, consciously representing a final state of non-consciousness poses formidable, if not impassable, cognitive constraints. By relying on simulation strategies to derive information about the minds of dead agents, you would in principle be compelled to "put yourself into the shoes" of such organisms, which is of course an impossible task. These constraints may lead to a number of telltale errors, namely Type I errors (inferring mental states when in fact there are none), regarding the psychological status of dead agents. Several decades ago, the developmental psychologist Gerald Koocher described, for instance, how a group of children tested on death comprehension reflected on what it might be like to be dead "with references to sleeping, feeling 'peaceful,' or simply 'being very dizzy.'" More recently, my colleague David Bjorklund and I found evidence that younger children are more likely to attribute mental states to a dead agent than are older children, which is precisely the opposite pattern that one would expect to find if the origins of such beliefs could be traced exclusively to cultural learning.

It seems that the default cognitive stance is reasoning that human minds are immortal; the steady accretion of scientific facts may throw off this stance a bit, but, as Unamuno found out, even science cannot answer the "big" question. Don't get me wrong. Like Unamuno, I don't believe in the afterlife. Recent findings have led me to believe that it's all a cognitive illusion churned up by a psychological system specially designed to think about unobservable minds. The soul is distinctly human all right. Without our evolved capacity to reason about minds, the soul would never have been. But in this case, the proof isn't in the empirical pudding. It can't be. It's death we're talking about, after all.

Psychologist, University of Massachusetts, Amherst; Author, The Cognitive Brain
Psychologist, University of Massachusetts, Amherst; Author, The Cognitive Brain

I have proposed a law of conscious content which asserts that for any experience, thought, question, or solution, there is a corresponding analog in the biophysical state of the brain. As a corollary to this principle, I have argued that conventional attempts to understand consciousness by simply searching for the neural correlates of consciousness (NCC) in theoretical and empirical investigations are too weak to ground a good understanding of conscious content. Instead, I have proposed that we go beyond NCC and explore brain events that have at least some similarity to our phenomenal experiences, namely, neuronal analogs of conscious content (NAC). In support of this approach, I have presented a theoretical model that goes beyond addressing the sheer correlation between mental states and neuronal events in the brain. It explains how neuronal analogs of phenomenal experience (NAC) can be generated, and it details how other essential human cognitive tasks can be accomplished by the particular structure and dynamics of putative neuronal mechanisms and systems in the brain.

A large body of experimental findings, clinical findings, and phenomenal reports can be explained within a coherent framework by the neuronal structure and dynamics of my theoretical model. In addition, the model accurately predicts many classical illusions and perceptual anomalies. So I believe that the neuronal mechanisms and systems that I have proposed provide a true explanation for many important aspects of human cognition and phenomenal experience. But I can't prove it. Of course, competing theories about the brain, cognition, and consciousness can't be proved either. But I can't prove it. Providing the evidence is the best we can do—I think.

Professor and Chairman of Computer Science, Brandeis University
Computer Scientist, Brandeis University

I believe that that systems of self-interested agents can make progress on their own without centralized supervision.

There is an isomorphism between evolution, economics, and education. In economics, the supervisor is a central government or super rich investor, in evolution, it is the "intelligent designer", and in education, its the teacher or outside examiners. In economic systems, despite an almost religious belief in Laissez-Faire and incentive-based behavior, economic systems are prone to winner-take-all phenomena and boom-bust cycles. They seem to require benevolent regulation, or "managed competition" to prevent the "rich get richer" dynamic leading to monopoly, which leads inevitably to corruption and kleptocracy. In evolution, scientists reject the intelligent designer as a creationist ruse, but so far our working models for open-ended evolution haven't worked, and prematurely convergence to mediocrity. In education, evidence of auto-didactic learning in video-games and sports is suppressed in academics by top-down curriculum frameworks and centralized high-stakes testing. 

If we did have a working mechanism design which could achieve continuous progress by decentralized self-interested agents, it would settle the creationist objection as well as apply to the other fields, leading to a new renaissance.

Professor of Quantum Mechanical Engineering, MIT; Author, Programming the Universe
Quantum Mechanical Engineer, Massachusetts Institute of Technology

I believe in science. Unlike mathematical theorems, scientific results can't be proved.They can only be tested again and again, until only a fool would not believe them.

I cannot prove that electrons exist, but I believe fervently in their existence. And if you don't believe in them, I have a high voltage cattle prod I'm willing to apply as an argument on their behalf. Electrons speak for themselves.

retired director of the American Institute of Physics
Physicist; Retired director, American Institute of Physics; Author, The Quantum World

I believe that microbial life exists elsewhere in our galaxy.

I am not even saying "elsewhere in the universe." If the proposition I believe to be true is to be proved true within a generation or two, I had better limit it to our own galaxy. I will bet on its truth there.

I believe in the existence of life elsewhere because chemistry seems to be so life-striving and because life, once created, propagates itself in every possible direction. Earth's history suggests that chemicals get busy and create life given any old mix of substances that includes a bit of water, and given practically any old source of energy; further, that life, once created, spreads into every nook and cranny over a wide range of temperature, acidity, pressure, light level, and so on.

Believing in the existence of intelligent life elsewhere in the galaxy is another matter. Good luck to the SETI people and applause for their efforts, but consider that microbes have inhabited Earth for at least 75 percent of its history, whereas intelligent life has been around for but the blink of an eye, perhaps 0.02 percent of Earth's history (and for nearly all of that time without the ability to communicate into space). Perhaps intelligent life will have staying power. We don't know. But we do know that microbial life has staying power.

Now to a supposition: that Mars will be found to have harbored life and harbors life no more. If this proves to be the case, it will be an extraordinarily sobering discovery for humankind, even more so than the view of our fragile blue ball from the Moon, even more so than our removal from the center of the universe by Copernicus, Galileo, and Newton—perhaps even more so than the discovery of life elsewhere in the galaxy.

Editor-in-chief of Discover Magazine
Editor-in-Chief, Discover Magazine

I believe that life is common throughout the universe and that we will find another Earth-like planet within a decade.

The mathematics alone ought to be proof to most people (billions of galaxies with billions of stars in each galaxy and around most of those stars are planets). The numbers suggest that for life not to exist elsewhere in the universe is the unlikely scenario. But there is more to this idea than a good chance. We've now found more than 130 planets just looking at nearby stars in our tiny little corner of the Milky Way. The results suggest there are uncountable numbers of planets in our galaxy alone. Some of them are likely to be earthlike, or at least earth-sized, although the vast majority that we've found so far are huge gas giants like Jupiter and Saturn which are unlikely to harbor life. Furthermore, there were four news events this year that made the discovery of life elsewhere extraordinarily more likely.

First, the NASA Mars Rover called Opportunity found incontrovertible evidence that a briny--salty-sea once covered the area where it landed, called Meridiani Planum. The only question about life on Mars now is whether that sea—which was there twice in Martian history—existed long enough for life to form. The Phoenix mission in 2008 may answer that question.

Second, a team of astrophysicists reported in July that radio emissions from Sagittarius B2, a nebula near the center of the Milky Way, indicate the presence of aldehyde molecules, the prebiotic stuff of life. Aldehydes help form amino acids, the fundamental components of proteins. The same scientists previously reported clouds of other organic molecules in space, including glycolaldehyde, a simple sugar. Outer space is thus full of complex molecules—not just atoms—necessary for life. Comets in other solar systems could easily deposit such molecules on planets, as they may have done in our solar system with earth. 

Third, astronomers in 2004 found much smaller planets around other stars for the first time. Barbara McArthur at the University of Texas at Austin found a planet 18 times the mass of Earth around 55 Cancri, a star with three other known planets. A team in Portugal announced finding a 14-mass planet. These smaller planets are likely to be rock, not gas. McArthur says, "We're on our way to finding an extrasolar earth."

Fourth, astronomers are not only getting good at finding new planets around other stars, they're getting the resolution of the newest telescopes so good that they can see the dim light from some newly found planets. Meanwhile, even better telescopes are being built, like the large binocular scope on Mt. Graham in Arizona that will see more planets. With light we can analyze the spectrum a new planet reflects and determine what's on that planet—like water. Water, we also discovered recently is abundant in space in large clouds between and near stars.

So everything life needs is out there. For it not to come together somewhere else as it did on earth is remarkably unlikely. In fact, although there are Goldilocks zones in galaxies where life as we know it is most likely to survive (there's too much radiation towards the center of the Milky Way, for example), there are almost countless galaxies out there where conditions could be ripe for life to evolve. This is a golden age of astrophysics and we're going to find life elsewhere.

Psychologist, Autism Research Centre, Cambridge University; Author, The Science of Evil
Psychologist, Autism Research Centre, Cambridge University; Author, The Essential Difference

I am not interested in ideas that cannot in principle be proven or disproven. I am as capable as the next guy in believing in an idea that is not yet proven so long as it could in principle be proven or disproven.

In my chosen field of autism, I believe that the cause will turn out to be assortative mating of two hyper-systemizers. I believe this because we already have 3 pieces of the jig-saw: (1) that fathers of children with autism are more likely to work in the field of engineering (compared to fathers of children without autism); (2) that grandfathers of children with autism—on both sides of the family—were also more likely to work in the field of engineering (compared to grandfathers of children without autism); and (3) that both mothers and fathers of children with autism are super-fast at the embedded figures test, a task requiring analysis of patterns and rules. (Note that engineering is a chosen example because it involves strong systemizing. But other related scientific and technical fields [such as math or physics] would have been equally good examples to study).

We have had these three pieces of the jigsaw since 1997, published in the scientific literature. They do not yet prove the assortative mating theory. They simply point to it being highly likely. Direct tests of the theory are still needed. I will be the first to give up this idea if it is proven wrong, since I'm not in the business of holding onto wrong ideas. But I won't give up the idea simply because it will be unpopular to certain groups (such as those who want to believe that the cause of autism is purely environmental). I will hold onto the idea until it has been properly tested. Popperian science is about being able to let go of an idea when the evidence goes against it, but it is also about being able to hold onto an idea until the evidence has been collected, if you have enough reasons to believe it might be true.

The causes of autism are likely to be complex, including at the very least multiple genes interacting with environmental factors, but the assortative mating theory may describe some contributing factors.

Professor of Biology and Mathematics, Harvard University; coathor, SuperCooperators
Biological Mathematician, Harvard University; Director, Center for Evolutionary Dynamics

I believe the following aspects of evolution to be true without knowing how to turn them into (respectable) research topics.

Important steps in evolution are robust. Multi-cellularity evolved at least ten times. There are several independent origins of eusociality. There were a number of lineages leading from primates to humans. If our ancestors would not have evolved language, somebody else would have.

Cooperation and language define humanity. Every special trait of humans is derivative of language.

Mathematics is a language and therefore a product of evolution.

Cognitive Scientist, UC, Irvine; Author, Visual Intelligence
Cognitive Scientist, UC, Irvine; Author, Visual Intelligence

I believe that consciousness and its contents are all that exists. Spacetime, matter and fields never were the fundamental denizens of the universe but have always been, from their beginning, among the humbler contents of consciousness, dependent on it for their very being.

The world of our daily experience—the world of tables, chairs, stars and people, with their attendant shapes, smells, feels and sounds—is a species-specific user interface to a realm far more complex, a realm whose essential character is conscious. It is unlikely that the contents of our interface in any way resemble that realm. Indeed the usefulness of an interface requires, in general, that they do not. For the point of an interface, such as the windows interface on a computer, is simplification and ease of use. We click icons because this is quicker and less prone to error than editing megabytes of software or toggling voltages in circuits. Evolutionary pressures dictate that our species-specific interface, this world of our daily experience, should itself be a radical simplification, selected not for the exhaustive depiction of truth but for the mutable pragmatics of survival.

If this is right, if consciousness is fundamental, then we should not be surprised that, despite centuries of effort by the most brilliant of minds, there is as yet no physicalist theory of consciousness, no theory that explains how mindless matter or energy or fields could be, or cause, conscious experience. There are, of course, many proposals for where to find such a theory—perhaps in information, complexity, neurobiology, neural darwinism, discriminative mechanisms, quantum effects, or functional organization. But no proposal remotely approaches the minimal standards for a scientific theory: quantitative precision and novel prediction. If matter is but one of the humbler products of consciousness, then we should expect that consciousness itself cannot be theoretically derived from matter. The mind-body problem will be to physicalist ontology what black-body radiation was to classical mechanics: first a goad to its heroic defense, later the provenance of its final supersession.

The heroic defense will, I suspect, not soon be abandoned. For the defenders doubt that a replacement grounded in consciousness could attain the mathematical precision or impressive scope of physicalist science. It remains to be seen, of course, to what extent and how effectively mathematics can model consciousness. But there are fascinating hints: According to some of its interpretations, the mathematics of quantum theory is itself, already, a major advance in this project. And perhaps much of the mathematical progress in the perceptual and cognitive sciences can also be so interpreted. We shall see.

The mind-body problem may not fall within the scope of physicalist science, since this problem has, as yet, no bona fide physicalist theory. Its defenders can surely argue that this penury shows only that we have not been clever enough or that, until the right mutation chances by, we cannot be clever enough, to devise a physicalist theory. They may be right. But if we assume that consciousness is fundamental then the mind-body problem transforms from an attempt to bootstrap consciousness from matter into an attempt to bootstrap matter from consciousness. The latter bootstrap is, in principle, elementary: Matter, spacetime and physical objects are among the contents of consciousness.

The rules by which, for instance, human vision constructs colors, shapes, depths, motions, textures and objects, rules now emerging from psychophysical and computational studies in the cognitive sciences, can be read as a description, partial but mathematically precise, of this bootstrap. What we lose in this process are physical objects that exist independent of any observer. There is no sun or moon unless a conscious mind perceives them, for both are constructs of consciousness, icons in a species-specific user interface. To some this seems a patent absurdity, a reductio of the position, readily contradicted by experience and our best science. But our best science, our theory of the quantum, gives no such assurance. And experience once led us to believe the earth flat and the stars near. Perhaps, in due time, mind-independent objects will go the way of flat earth.

This view obviates no method or result of science, but integrates and reinterprets them in its framework. Consider, for instance, the quest for neural correlates of consciousness (NCC). This holy grail of physicalism can, and should, proceed unabated if consciousness is fundamental, for it constitutes a central investigation of our user interface. To the physicalist, an NCC is, potentially, a causal source of consciousness. If, however, consciousness is fundamental, then an NCC is a feature of our interface correlated with, but never causally responsible for, alterations of consciousness. Damage the brain, destroy the NCC, and consciousness is, no doubt, impaired. Yet neither the brain nor the NCC causes consciousness. Instead consciousness constructs the brain and the NCC. This is no mystery. Drag a file's icon to the trash and the file is, no doubt, destroyed. Yet neither the icon nor the trash, each a mere pattern of pixels on a screen, causes its destruction. The icon is a simplification, a graphical correlate of the file's contents (GCC), intended to hide, not to instantiate, the complex web of causal relations.

Business Affairs Editor, The Economist; Author, The Edible History of the Humanity
Technology Editor, The Economist

I believe that the radiation emitted by mobile phones is harmless.

My argument is not based so much on the scientific evidence—because there isn't very much of it, and what little there is has either found no effect or is statistically dubious. Instead, it is based on a historical analogy with previous scares about overhead power lines and cathode-ray computer monitors (VDUs). Both were also thought to be dangerous, yet years of research—decades in the case of power lines—failed to find conclusive evidence of harm.

Mobile phones seem to me to be the latest example of what has become a familiar pattern: anecdotal evidence suggests that a technology might be harmful, and however many studies fail to find evidence of harm, there are always calls for more research.

The underlying problem, of course, is the impossibility of proving a negative. During the fuss over genetically modified crops in Europe, there were repeated calls for proof that GM technology was safe. Similarly, in the aftermath of the BSE scare in Britain, scientists were repeatedly asked for proof that beef was safe to eat. But you cannot prove that something has no effect: absence of evidence is not evidence of absence. All you can do is look for evidence of harm. If you don't find it, you can look again. If you still fail to find it, the question is still open: "lack of evidence of harm" means both "safe as far as we can tell" and "we still don't know if it's safe or not". Scientists are often unfairly accused of logic-chopping when they point this out.

Looking back even further, I expect mobile phones will turn out to be merely the latest in a long line of technologies that raised health concerns that subsequently turned out to be unwarranted. In the 19th century, long before the power-line and VDU scares, telegraph wires were accused of affecting the weather, and railway travel was believed to cause nervous disorders.

The irony is that since my belief that mobile phones are safe is based on a historical analysis, I am on no firmer ground scientifically than those who believe mobile phones are harmful. Still, I believe they are safe, though I can't prove it.

Physicist, Computer Scientist, Chairman of Applied Minds, Inc.; author, The Pattern on the Stone
Physicist, Computer Scientist; Chairman, Applied Minds, Inc.; Author, The Pattern on the Stone

I know that it sounds corny, but I believe that people are getting better. In other words, I believe in moral progress. It is not a steady progress, but there is a long-term trend in the right direction—a two steps forward, one step back kind of progress.

I believe, but cannot prove, that our species is passing through a transitional stage, from being animals to being true humans. I do not pretend to understand what true humans will be like, and I expect that I would not even understand it if I met them. Yet, I believe that our own universal sense of right and wrong is pointing us in the right direction, and that it is the direction of our future. 

I believe that ten thousand years from now, people (or whatever we are by then) will be more empathetic and more altruistic than we are. They will trust each other more, and for good reason. They will take better care of each other. They be more thoughtful about the broader consequences of their actions. They will take better care of their future than we do of ours.

Philosopher; Founder and Editor, Arts & Letters Daily; Author, The Art Instinct
Philosopher of Art, University of Canterbury, New Zealand; Editor, Arts & Letters Daily

In a 1757 essay, philosopher David Hume argued that because "the general principles of taste are uniform in human nature" the value of some works of art might be essentially eternal. He observed that the "same Homer who pleased at Athens and Rome two thousand years ago, is still admired at Paris and London." The works that manage to endure over millennia, Hume thought, do so precisely because they appeal to deep, unchanging features of human nature.

Some unique works of art, for example, Beethoven's Pastoral Symphony, possess this rare but demonstrable capacity to excite the human mind across cultural boundaries and through historic time. I cannot prove it, but I think a small body of such works—by Homer, Bach, Shakespeare, Murasaki Shikibu, Vermeer, Michelangelo, Wagner, Jane Austen, Sophocles, Hokusai—will be sought after and enjoyed for centuries or millennia into the future. As much as fashions and philosophies are bound to change, these works will remain objects of permanent value to human beings.

These epochal survivors of art are more than just popular. The majority of works of popular art today are not inevitably shallow or worthless, but they tend to be easily replaceable. In the modern mass art system, artistic forms endure, while individual works drop away. Spy thrillers, romance novels, pop songs, and soap operas are daily replaced by more thrillers, romance novels, pop songs, and soap operas. In fact, the ephemeral nature of mass art seems more pronounced than ever: most popular works are incapable of surviving even a year, let alone a couple of generations. It's different with art's classic survivors: even if they began, as Sophocles' and Shakespeare's did, as works of popular art, they set themselves apart in their durable appeal: nothing kills them. Audiences keep coming back to experience these original works themselves.

Against the idea of permanent aesthetic values is cultural relativism, which is taught as the default orthodoxy in many university departments. Aesthetic values have been widely construed by academics as merely contingent reflections of local social and economic conditions. Beauty, if not in the eye of the beholder, has been misconstrued as merely in the eyes of society, a conditioning that determines values of cultural seeing. Such veins of explanation often include no small amount of cynicism: why do people go to the opera? Oh, to show off their furs. Why are they thrilled by famous paintings? Because they're worth millions. Beneath such explanations is a denial of intrinsic aesthetic merit.

Such aesthetic relativism is decisively refuted, as Hume understood, by the cross-cultural appeal of a small class of art objects over centuries: Mozart packs Japanese concerts halls, as Hiroshige does Paris galleries, while new productions of Shakespeare in every major language of the world are endless. And finally, it is beginning to look as though empirical psychology is equipped to address the universality of art. For example, evolutionary psychology is being used by literary scholars to explain the persistent themes and plot devices in fiction. The rendering of faces, bodies, and landscape preferences in art is amenable to psychological investigation. The structure of musical perception is now open to experimental analysis as never before. Poetic experience can be elucidated by the insights of contemporary linguistics. None of this research promises a recipe for creating great art, but it can throw light on what we already know about aesthetic pleasure.

What's going on most days in the Metropolitan Museum and most nights at Lincoln Center involves aesthetic experiences that will be continuously revived and relived by our descendents into an indefinite future. In a way, this makes the creations of the greatest artists as much permanent achievements as the discoveries of greatest scientists. That much I think I know. The question we should now ask is, What makes this possible? What is it about the highest works of art that gives them eternal appeal?

Director emeritus of Fermi National Accelerator Laboratory
Physicist and Nobel Laureate; Director Emeritus, Fermilab; Coauthor, The God Particle

My friend, the theoretical physicist, believed so strongly in String Theory, "It must be true!" He was called to testify in a lawsuit, which contested the claims of String Theory against Quantum Loop Gravity. The lawyer was skeptical. "What makes you such an authority?" he asked. "Oh, I am without question the world's most outstanding theoretical physicist", was the startling reply. It was enough to convince the lawyer to change the subject. However, when the witness came off the stand, he was surrounded by protesting colleagues.

"How could you make such an outrageous claim?" they asked. The theoretical physicist defended, "Fellows, you just don't understand; I was under oath."

To believe without knowing it cannot be proved (yet) is the essence of physics. Guys like Einstein, Dirac, Poincaré, etc. extolled the beauty of concepts, in a bizarre sense, placing truth at a lower level of importance. There are enough examples that I resonated with the arrogance of my theoretical masters who were in effect saying that God, a.k.a. the Master, Der Alte, may have, in her fashioning of the universe, made some errors in favoring of a convenient truth over a breathtakingly wondrous mathematics. This inelegant lack of confidence has heretofore always proved hasty. Thus, when the long respected law of mirror symmetry was violated by weakly interacting but exotic particles, our pain at the loss of simplicity and harmony was greatly alleviated by the discovery of the failure of particle-antiparticle symmetry. The connection was exciting because the simultaneous reflection in a mirror and change of particles to antiparticles seemed to restore a new and more powerful symmetry—"CP" symmetry now gave us a connection of space (mirror reflection) and electric charge. How silly of us to have lost confidence in the essential beauty of nature!

The renewed confidence remained even when it turned out that "CP" was also imperfectly respected. "Surely," we now believe, "there is in store some spectacular, new, unforeseen splendor in all of us." She will not let us down. This we believe, even though we can't prove it.

Research Professor/Professor Emeritus, University of Maryland, Baltimore; Author, Curious Behavior: Behavior: Yawning, Laughing, Hiccupping, and Beyond
Psychologist and Neuroscientist, University of Maryland; Author, Laughter

Human Behavior is Unconsciously Controlled.

Until proven otherwise, why not assume that consciousness does not play a role in human behavior? Although it may seem radical on first hearing, this is actually the conservative position that makes the fewest assumptions. The null position is an antidote to philosopher's disease, the inappropriate attribution of rational, conscious control over processes that may be irrational and unconscious. The argument here is not that we lack consciousness, but that we over-estimate the conscious control of behavior. I believe this statement to be true. But proving it is a challenge because it's difficult to think about consciousness. We are misled by an inner voice that generates a reasonable but often fallacious narrative and explanation of our actions. That the beam of conscious awareness that illuminates our actions is on only part of the time further complicates the task. Since we are not conscious of our state of unconsciousness, we vastly overestimate the amount of time that we are aware of our own actions, whatever their cause.

My thinking about unconscious control was shaped by my field studies of the primitive play vocalization of laughter. When I asked people to explain why they laughed in a particular situation, they would concoct some reasonable fiction about the cause of their behavior—"someone did something funny," "it was something she said," "I wanted to put her at ease." Observations of social context showed that such explanations were usually wrong. In clinical settings, such post hoc misattributions would be termed "confabulations," honest but flawed attempts to explain one's actions.

Subjects also incorrectly presumed that laughing is a choice and under conscious control, a reason for their confident, if bogus, explanations of their behavior. But laughing is not a matter speaking "ha-ha," as we would choose a word in speech. When challenged to laugh on command, most subjects could not do so. In certain, usually playful, social contexts, laughter simply happens. However, this lack of voluntary control does not preclude a lawful pattern of behavior. Laughter appears at those places where punctuation would appear in a transcription of a conversation—laughter seldom interrupts the phrase structure of speech. We may say, "I have to go now—ha-ha," but rarely, "I have to—ha-ha—go now." This punctuation effect is highly reliable and requires the coordination of laughing with the linguistic structure of speech, yet it is performed without conscious awareness of the speaker. Other airway maneuvers such as breathing and coughing punctuate speech and are performed without speaker awareness.

The discovery of lawful but unconsciously controlled laughter produced by people who could not accurately explain their actions led me to consider the generality of this situation to other kinds of behavior. Do we go through life listening to an inner voice that provides similar confabulations about the causes of our action? Are essential details of the neurological process governing human behavior inaccessible to introspection? Can the question of animal consciousness be stood on its head and treated in a more parsimonious manner? Instead of considering whether other animals are conscious, or have a different, or lesser consciousness than our own, should we question if our behavior is under no more conscious control than theirs? The complex social order of bees, ants, and termites documents what can be achieved with little, if any, conscious control as we think of it. Is machine consciousness possible or even desirable? Is intelligent behavior a sign of conscious control? What kinds of tasks require consciousness? Answering these questions requires an often counterintuitive approach to the role, evolution and development of consciousness.

Social Psychologist; Hope College; Author, Psychology, 10th Edition
Psychologist, Hope College; Author, Intuition

As a Christian monotheist, I start with two unproven axioms:

1. There is a God.

2. It's not me (and it's also not you).

Together, these axioms imply my surest conviction: that some of my beliefs (and yours) contain error. We are, from dust to dust, finite and fallible. We have dignity but not deity.

And that is why I further believe that we should

a) hold all our unproven beliefs with a certain tentativeness (except for this one!),

b) assess others' ideas with open-minded skepticism, and

c) freely pursue truth aided by observation and experiment.

This mix of faith-based humility and skepticism helped fuel the beginnings of modern science, and it has informed my own research and science writing. The whole truth cannot be found merely by searching our own minds, for there is not enough there. So we also put our ideas to the test. If they survive, so much the better for them; if not, so much the worse.

Within psychology, this "ever-reforming" process has many times changed my mind, leading me now to believe, for example, that newborns are not so dumb, that electro convulsive therapy often alleviates intractable depression, that America's economic growth has not improved our morale, that the automatic unconscious mind dwarfs the conscious mind, that traumatic experiences rarely get repressed, that most folks don't suffer low self-esteem, and that sexual orientation is not a choice.

Publisher, Skeptic magazine; monthly columnist, Scientific American; Author, The Moral Arc , and Presidential Fellow at Chapman University.
Publisher, Skeptic magazine; Columnist, Scientific American; Author Science Friction

I believe, but cannot prove...that reality exists over and above human and social constructions of that reality. Science as a method, and naturalism as a philosophy, together form the best tool we have for understanding that reality. Because science is cumulative—that is, it builds on itself in a progressive fashion—we can strive to achieve an ever-greater understanding of reality. Our knowledge of nature remains provisional because we can never know if we have final Truth. Because science is a human activity and nature is complex and dynamic, fuzzy logic and fractional probabilities best describe both nature and the estimations of our approximation toward understanding that nature.

There is no such thing as the paranormal and the supernatural; there is only the normal and the natural and mysteries we have yet to explain.

What separates science from all other human activities is its belief in the provisional nature of all conclusions. In science, knowledge is fluid and certainty fleeting. That is the heart of its limitation. It is also its greatest strength. There are, from this ultimate unprovable assertion, three additional insoluble derivatives.

1. There is no God, intelligent designer, or anything resembling the divinity as proffered by the world's religions (although an extra-terrestrial being of significantly greater intelligence and power than us would be indistinguishable from God).

After thousands of years of the world's greatest minds attempting to prove or disprove the divinity's existence or nonexistence, with little agreement or consensus amongst scholars as to the divinity's ultimate state of being, a reasonable conclusion is that the God question can never be solved and that one's belief, disbelief, or skepticism ultimately rests on a non-rational basis.

2. The universe is ultimately determined, but we have free will.

As with the God question, scholars of considerable intellectual power for many millennia have failed to resolve the paradox of feeling free in a determined universe. One provisional solution is to think of the universe as so complex that the number of causes and the complexity of their interactions make the predetermination of human action pragmatically impossible. We can even put a figure on the causal net of the universe to see just how absurd it is to think we can get our minds around it fully.

It has been computed that in order for a computer in the far future of the universe to resurrect in a virtual reality every person who ever lived or could have lived, with all causal interactions between themselves and their environment, it would need 10 to the power of 10 to the power of 123 bits (a 1 followed by 10^123 zeros) of memory. Suffice it to say that no computer within the conceivable future will achieve this level of power; likewise no human brain even comes close.

The enormity of this complexity leads us to feel as if we are acting freely as uncaused causers, even though we are actually causally determined. Since no set of causes we select as the determiners of human action can be complete, the feeling of freedom arises out of this ignorance of causes. To that extent we may act as if we are free. There is much to gain, little to lose, and personal responsibility follows.

3. Morality is the natural outcome of evolutionary and historical forces, not divine command. 

The moral feelings of doing the right thing (such as virtuousness) or doing the wrong thing (such as guilt) were generated by nature as part of human evolution.

Although cultures differ on what they define as right and wrong, the moral feelings of doing the right or wrong thing are universal to all humans. Human universals are pervasive and powerful, and include at their core the fact that we are, by nature, moral and immoral, good and evil, altruistic and selfish, cooperative and competitive, peaceful and bellicose, virtuous and non-virtuous. Individuals and groups vary on the expression of such universal traits, but everyone has them. Most people, most of the time, in most circumstances, are good and do the right thing for themselves and for others. But some people, some of the time, in some circumstances, are bad and do the wrong thing for themselves and for others.

As a consequence, moral principles are provisionally true, where they apply to most people, in most cultures, in most circumstances, most of the time. At some point in the last 10,000 years (around the time of writing and the shift from bands and tribes to chiefdoms and states around 5,000 years ago) religions began to codify moral precepts into moral codes, and political states began to codify moral precepts into legal codes.

In conclusion, I believe, but cannot prove...that reality exists and science is the best method for understanding it, there is no God, the universe is determined but we are free, morality evolved as an adaptive trait of humans and human communities, and that ultimately all of existence is explicable through science.

Of course, I could be wrong...

Brooks and Suzanne Ragen Professor of Psychology, Yale University; Author, Just Babies: The Origins of Good and Evil
Psychologist, Yale University; Author, Descartes' Baby

John MacNamara once proposed that children come to learn about right and wrong, good and evil, in much the same way that they learn about geometry and mathematics. Moral development is not merely cultural learning, and it does not arise from innate principles that have evolved through natural selection. It is not like the development of language or sexual preference or taste in food. 

Instead, moral development involves the construction of a intricate formal system that makes contact with the external world in a significant way. This cannot be entirely right. We know that gut-feelings, such as reactions of empathy or disgust, have a major influence on how children and adults reason about morality. And no serious theory of moral development can ignore the role of natural selection in shaping our moral intuitions. But what I like about Macnamara's proposal is that it allows for moral realism. It allows for the existence of moral truths that people come to discover, just as we come to discover truths of mathematics. We can reject the nihilistic position (help by many researchers) that our moral intuitions are nothing more than accidents of biology or culture. 

And so I believe (though I cannot prove it) that the development of moral reasoning is the same sort of process as the development of mathematical reasoning.

Catalyst, Information Technology Startups, EDventure Holdings, Former Chariman,Electronic Frontier Foundation and ICANN; Author: Release 2.1
Editor of Release 1.0; Trustee, Long Now Foundation; Author, Release 2.0

We're living longer, and thinking shorter.

[Disclaimer: Since I'm not a scientist, I'm not even going to attempt to take on something scientific. Rather, I want to talk about something that can't easily be measured, let alone proved.

And second, though what I'm saying may sound gloomy, I love the times we live in. There has never been a time more interesting, more full of things to explain, interesting people to meet, worthy causes to support, challenging problems to solve.]

It's all about time.

I think modern life has fundamentally and paradoxically changed our sense of time. Even as we live longer, we seem to think shorter. Is it because we cram more into each hour? Or because the next person over seems to cram more into each hour?

For a variety of reasons, everything is happening much faster and more things are happening. Change is a constant.

It used to be that machines automated work, giving us more time to do other things. But now machines automate the production of attention-consuming information, which takes our time. For example, if one person sends the same e-mail message to 10 people, then 10 people have to respond.

The physical friction of everyday life—the time it took Isaac Newton to travel by coach from London to Cambridge, the dead spots of walking to work (no iPod), the darkness that kept us from reading—has disappeared, making every minute not used productively into an opportunity cost.

And finally, we can measure more, over smaller chunks of time. From airline miles to calories (and carbs and fat grams), from friends on Friendster to steps on a pedometer, from realtime stock prices to millions of burgers consumed, we count things by the minute and the second.

Unfortunately, this carries over into how we think and plan: Businesses focus on short-term results; politicians focus on elections; school systems focus on test results; most of us focus on the weather rather than the climate. Everyone knows about the big problems, but their behavior focuses on the here and now.

I first noticed this phenomenon in a big way in the US right after 9/11, when it became impossible to schedule an appointment or get anyone to make a commitment. To me, it felt like Russia (where I had been spending time since 1989), where people avoided long-term plans because there was little discernible relationship between effort and result. Suddenly, even in the US, people were behaving like the Russians of those days, reluctant to plan for anything more than a few days out.

Of course, that immediate crisis has passed, but there's still the same sense of unpredictability dogging our thinking in the US (in particular). Best to concentrate on the current quarter, because who knows what job I'll have next year. Best to pass that test, because what I actually learn won't be worth much ten years from now anyway.

How can we reverse this?

It's a social problem, but I think it may also herald a mental one—which I describe as mental diabetes.

Whatever's happening to adults, most of us grew up reading books (at least occasionally) and playing with "uninteractive" toys that required us to make up our own stories, dialogue and behavior for them. Today's children are living in an information-rich, time-compressed environment that often seems to replace a child's imagination rather than stimulate it. I posit that being fed so much processed information—video, audio, images, flashing screens, talking toys, simulated action games—is akin to being fed too much processed, sugar-rich food. It may seriously mess up children's information metabolism and their ability to process information for themselves. In other words, will they be able to discern cause and effect, to put together a coherent story line, to think scientifically?

I don't know the answers, but these questions are worth thinking about, for the long term.

Financier and Science Philanthropist
Money Manager and Science Philanthropist

The great breakthrough will involve a new understanding of time...that moving through time is not free, and that consciousness itself will be seen to only be a time sensor, adding to the other sensors of light and space.

Philosopher, Novelist; Author, Betraying Spinoza; 36 Arguments for the Existence of God: A Work of Fiction
Philosopher and Novelist, Trinity College; Author, Incompleteness

I believe that scientific theories are a means of going—somewhat mysteriously—beyond what we are able to observe of the physical world, penetrating into the structure of nature. The "theoretical" parts of scientific theories—the parts that speak in seemingly non-observational terms—aren't, I believe, ultimately translatable into observations or aren't just algorithmic black boxes into which we feed our observations and churn out our predictions. I believe the theoretical parts have descriptive content and are true (or false) in the same prosaic way that the observational parts of theories are true (or false). They're true if and only if they correspond to reality.

I also believe that my belief about scientific theories isn't itself scientific. Science itself doesn't decide how it is to be interpreted, whether realistically or not.

That the penetration into unobservable nature is accomplished by way of abstract mathematics is a large part of what makes it mystifying—mystifying enough to be coherently if unpersuasively (at least to me) denied by scientific anti-realists. It's difficult to explain exactly how science manages to do what it is that I believe it does—notoriously difficult when trying to explain how quantum mechanics, in particular, describes unobserved reality. The unobservable aspects of nature that yield themselves to our knowledge must be both mathematically expressible and connected to our observations in requisite ways. The seventeenth-century titans, men like Galileo and Newton, figured out how to do this, how to wed mathematics to empiricism. It wasn't a priori obvious that it was going to work. It wasn't a priori obvious that it was going to get us so much farther into nature's secrets than the Aristotelian teleological methodology it was supplanting. A lot of assumptions about the mathematical nature of the world and its fundamental correspondence to our cognitive modes (a correspondence they saw as reflective of God's friendly intentions toward us) were made by them in order to justify their methodology.

I also believe that since not all of the properties of nature are mathematically expressible—why should they be? it takes a very special sort of property to be so expressible—that there are aspects of nature that we will never get to by way of our science. I believe that our scientific theories—just like our formalized mathematical systems (as proved by Gödel)—must be forever incomplete. The very fact of consciousness itself (an aspect of the material world we happen to know about, but not because it was revealed to us by way of science) demonstrates, I believe, the necessary incompleteness of scientific theories.

Professor Emeritus of Psychology at Stanford University; Author, The Lucifer Effect: Understanding How Good People Turn Evil
Psychologist, Emeritus Professor, Stanford University; Author, Shyness

I believe that the prison guards at the Abu Ghraib Prison in Iraq, who worked the night shift in Tier 1A, where prisoners were physically and psychologically abused, had surrendered their free will and personal responsibility during these episodes of mayhem. 

But I could not prove it in a court of law. These eight army reservists were trapped in a unique situation in which the behavioral context came to dominate individual dispositions, values, and morality to such an extent that they were transformed into mindless actors alienated from their normal sense of personal accountability for their actions—at that time and place.

The "group mind" that developed among these soldiers was created by a set of known social psychological conditions, some of which are nicely featured in Golding's Lord of the Flies. The same processes that I witnessed in my Stanford Prison Experiment were clearly operating in that remote place: Deindividuation, dehumanization, boredom, groupthink, role-playing, rule control, and more. Beyond the relatively benign conditions in my study, in that Iraqi prison, the guards experienced extreme fatigue and exhaustion from working 12-hour shifts, 7 days a week, for over a month at a time with no breaks.

There was fear of being killed from mortar and grenade attacks and from prisoners rioting. There was revenge for buddies killed, and prejudice against these foreigners for their strange religion and cultural traditions. There was encouragement by staff "to soften up" the detainees for interrogation because Tier 1A was the Interrogation-Soft Torture center of that prison. Already in place when these young men and women arrived there for their tour of duty were abusive practices that had been "authorized" from the top of the chain of command: Use of nakedness as a humiliation tactic, sensory and sleep deprivation, stress positions, dog attacks, and more.

In addition to the situational variables and processes operating in that behavioral setting were a serious of systemic processes that created the barrel into which these good soldiers were forced to live and work. Most of the reports of independent investigation committees cite a failure of leadership, lack of leadership, or irresponsible leadership as factors that contributed to these abuses. Then there was lack of mission-specific training of the guards, no oversight, no accountability to senior officers, poor resources, overcrowded facilities, confusing commands from civilian interrogators at odds with the CIA, military intelligence and other agencies and agents all working in Tier 1A without clear communication channels and much confusion.

I was recently an expert witness for the defense of Sgt. Ivan "Chip" Frederick in his Baghdad trial. Before the trial, I spent a day with him, giving him an in-depth interview, checking all background information, and arranging for him to be psychologically assessed by the military. He is one of the alleged "bad apples" who these investigations have labeled as "morally corrupt." What did he bring into that situation and what did that situation bring into him?

He seemed very much to be a normal young American. His psych assessments revealed no sign of any pathology, no sadistic tendencies, and all his psych assessment scores are in the normal range, as is his intelligence. He had been a prison guard at a small minimal security prison where he performed for many years without incident. So there is nothing in his background, temperament, or disposition that could have been a facilitating factor for the abuses he committed at the Abu Ghraib Prison.

After a four-day long trial, part of which included my testimony elaborating on the points noted here, the Judge took barely one hour to find him guilty of all eight counts and to sentence Sgt. Frederick to 8 years in prison, starting in solitary confinement in Kuwait, dishonorable discharge, broken in rank from Sgt. to Pvt., loss of his 20 years retirement income and his salary. This military judge held Frederick personally responsible for the abuses, because he had acted out of free will to intentionally harm these detainees since he was not forced into these acts, was not mentally incompetent, or acting in self-defense. All of the situational and systemic determinants of his behavior and that of his buddies were disregarded and given a zero weighting coefficient in assessing causal factors.

The real reason for the heavy sentence was the photographic documentation of the undeniable abuses along with the smiling abusers in their "trophy photos." It was the first time in history that such images were publicly available of what goes on in many prisons around the world, and especially in military prisons. They humiliated the military, and the entire chain of command all the way up the ladder to the White House. Following this exposure, investigations of all American military prisons in that area of the world uncovered similar abuses and worse, many murders of prisoners. Recent evidence has revealed that similar abuses started taking place again in Abu Ghraib prison barely one month after these disclosures became public—when the "Evil Eight Culprits" were in other prisons—as prisoners.

Based on more than 30 years of research on "The Lucifer Effect"—the transformation of good people into perpetrators of evil—I believe that there are powerful situational and systemic forces operating on individuals in certain situations that can undercut a lifetime of morality and rationality. The Dionysian aspect of human nature can triumph over the Apollonian, not only during Mardi Gras, but in dynamic group settings like gang rapes, fraternity hazing, mob riots, and in that Abu Ghraib prison. I believe in that truth in general and especially in the case of Sgt. Frederick, but I was not able to prove it in a military court of law.

Professor of Psychology, University of Texas, Austin; Coauthor: Why Women Have Sex; Author, The Dangerous Passion
Psychologist, University of Texas, Austin; Author, The Evolution of Desire

True love.

I've spent two decades of my professional life studying human mating. In that time, I've documented phenomena ranging from what men and women desire in a mate to the most diabolical forms of sexual treachery. I've discovered the astonishingly creative ways in which men and women deceive and manipulate each other. I've studied mate poachers, obsessed stalkers, sexual predators, and spouse murderers. But throughout this exploration of the dark dimensions of human mating, I've remained unwavering in my belief in true love.

While love is common, true love is rare, and I believe that few people are fortunate enough to experience it. The roads of regular love are well traveled and their markers are well understood by many—the mesmerizing attraction, the ideational obsession, the sexual afterglow, profound self-sacrifice, and the desire to combine DNA. But true love takes its own course through uncharted territory. It knows no fences, has no barriers or boundaries. It's difficult to define, eludes modern measurement, and seems scientifically wooly. But I know true love exists. I just can't prove it.

Psychologist; Director, Quality of Life Research Center, Claremont Graduate University; Author, Flow
Psychologist; Director, Quality of Life Research Center, Claremont Graduate University; Author, Flow

When I first read your question, I was sure it was a trick—after all, almost nothing I believe in I can prove. I believe the earth is round, but I cannot prove it, nor can I prove that the earth revolves around the sun or that the naked fig tree in the garden will have leaves in a few months. I can't prove quarks exist or that there was a Big Bang—all of these and millions of other beliefs are based on faith in a community of knowledge whose proofs I am willing to accept, hoping they will accept on faith the few measly claims to proof I might advance.

But then I realized—after reading some of the early postings—that every one else has assumed implicitly that the "you" in: "even if you cannot prove it" referred not to the individual respondent, but to the community of knowledge—it actually stood for "one" rather than for "you". That everyone seems to have understood this seems to me a remarkable achievement, a merging of the self with the collective that only great religions and profound ideologies occasionally achieve.

So what do I believe that no one else can prove? Not much, although I do believe in evolution, including cultural evolution, which means that I tend to trust ancient beliefs about good and bad, the sacred and the profane, the meaningful and the worthless—not because they are amenable to proof, but because they have been selected over time and in different situations, and therefore might be worthy of belief.

As to the future, I will follow the cautious weather forecaster who announces: "Tomorrow will be a beautiful day, unless it rains." In other words, I can see all sorts of potentially wonderful developments in human consciousness, global solidarity, knowledge and ethics; however, there are about as many trends operating towards opposite outcomes: a coarsening of taste, reduction to least common denominator, polarization of property, power, and faith. I hope we will have the time and opportunity to understand which policies lead to which outcomes, and then that we will have the motivation and the courage to implement the more desirable alternatives.

Social Psychologist; Professor, New York University Stern School of Business; Author, The Righteous Mind
Psychologist, University of Virginia

I believe, but cannot prove, that religious experience and practice is generated and structured largely by a few emotions that evolved for other reasons, particularly awe, moral elevation, disgust, and attachment-related emotions. That's not a prediction likely to raise any eyebrows in this forum.

But I further believe (and cannot prove) that hostility toward religion is an obstacle to progress in psychology. Most human beings live in a world full of magic, miracles, saints, and constant commerce with divinity. Psychology at present has little to say about these parts of life; we focus instead on a small set of topics that are fashionable, or that are particularly tractable with our favorite methods. If psychologists took religious experience seriously and tried to understand it from the inside, as anthropologists do with other cultures, I believe it would enrich our science. I have found religious texts and testimonials about purity and pollution essential for understanding the emotion of disgust.

Senior Consultant (& former Ed-in-Chief & Publishing Director) at New Scientist; Author, After the Ice: Life, Death, and Geopolitics in the New Arctic
Editor-in-Chief, New Scientist

Strangely, I believe that cockroaches are conscious. That is probably an unappealing thought to anyone who switches on a kitchen light in the middle of the night and finds a family of roaches running for cover. But it's really shorthand for saying that I believe that many quite simple animals are conscious, including more attractive beasts like bees and butterflies.

I can't prove that they are, but I think in principle it will be provable one day and there's a lot to be gained about thinking about the worlds of these relatively simple creatures, both intellectually—and even poetically. I don't mean that they are conscious in even remotely the same way as humans are; if that we were true the world would be a boring place. Rather the world is full of many overlapping alien consciousnesses.

Why do I think they might be multiple forms of conscious out there? Before becoming a journalist I spent 10 years and a couple of post-doctoral fellowships getting inside the sensory worlds of a variety of insects, including bees and cockroaches. I was inspired by A Picture Book of Invisible Worlds, a slim out-of-print volume by Jakob von Uexkull (1864-1944). 

The same book had also inspired Niko Tinbergen and Konrad Lorenz, the Nobel Prize winners who founded the field of ethology (animal behaviour). Von Uexkull studied the phenomenal world of animals, what he called their "umwelt", the worlds around animals as they themselves perceive them. Everything that an animals senses means something to it, for it has evolved to fit and create its world. Study of animals and their sensory worlds have now morphed into the field of sensory ecology, or on a wilder path, the newer science of biosemiotics.

I studied time studying how honey bees could find their way around my laboratory room (they had learnt to fly in through a small opening in the window) and find a hidden source of sugar. Bees could learn all about the pattern of key features in the room and would show they were confused if objects were moved around when they were out of the room. They were also easily distracted by certain kinds of patterns, particularly ones with lots of points and lines that had very abstract similarities to the patterns on flowers, as well as by floral scents, and by sudden movements that signalled danger. In contrast, when they were busy gorging on the sugar almost nothing could distract them, making it possible for myself to paint a little number on their backs so I distinguish individual bees.

To make sense of this ever changing behaviour, with its shifting focus of attention, I always found it simplest to figure out what was happening by imagining the sensory world of the bee, with its eye extraordinarily sensitive to flicker and colours we can't see, as a "visual screen" in the same way I can sit back and "see" my own visual screen of everything happening around me, with sights and sounds coming in and out of prominence. The objects in the bees world have significances or "meaning" quite different from our own, which is why its attention is drawn to things we would barely perceive.

That's what I mean by consciousness—the feeling of "seeing" the world and its associations. For the bee, it is the feeling of being a bee. I don't mean that a bee is self-conscious or spends time thinking about itself. But of course the problem of why the bee has its own "feeling" is the same incomprehensible "hard problem" of why the activity of our nervous system gives rise to our own "feelings".

But at least the bee's world is very visual and capable of being imagined. Some creatures live in sensory worlds that are much harder to access. Spiders that hunt at night live in a world dominated by the detection of faint vibration and of the tiniest flows of air that allow them to see fly passing by in pitch darkness. Sensory hairs that cover their body give them a sensitivity to touch far more finely grained than we can possibly feel through our own skin.

To think this way about simple creatures is not to fall into the anthropomorphic fallacy. Bees and spiders live in their own world in which I don't see human-like motives. Rather it is a kind of panpsychism, which I am quite happy to sign up to, at least until we know a lot more about the origin of consciousness. That may take me out of the company of quite a few scientists who would prefer to believe that a bee with a brain of only a million neurones must surely be a collection of instinctive reactions with some simple switching mechanism between then, rather have some central representation of what is going on that might be called consciousness. But it leaves me in the company of poets who wonder at the world of even lowly creatures.

"In this falling rain, 
where are you off to
snail?"

wrote the haiku poet Issa.

And as for the cockroaches, they are a little more human than the spiders. Like the owners of the New York apartments who detest them, they suffer from stress and can die from it, even without injury. They are also hierarchical and know their little territories well. When they are running for it, think twice before crushing out another world.

Physics Professor, Caltech; Experimental Physicist
Physicist, currently at CERN

I believe nothing to be true (clearly real) if it cannot be proved.

I'll take the question and make a pseudo-invariant transformation that makes it more apt to my brain. When Bohr was asked what is the complementary variable of "truth" (Wirklichkeit) he replied with no hesitation "clarity" (Klarheit). Contrary to Bohr, and since neither truth nor clarity are quantum mechanical variables, real truth and comprehensive clarity should be simultaneously achievable given rigorous experimental evidence. [In particular since "Wirklichkeit" means reality, and "Klarheit" is clarity in the sense of good understanding.]

In fact I will use clarity (as in "clear reality"), in the place of truth.

I will also invent equivalents for proof and for belief. Proof will be interchangeable with "experimental scientific evidence". Belief is more tricky given that it has to do with complex carbonic life. It can be interchangeable with "theoretical assessment" or "assessment by common sense" (depending on the scale and the available technology). In this process (no doubt in a path full of traps and pitfalls) I have cannibalized the original question to the following:

What do you (commonsensical/theoretically) assess to be clearly real even though you have no experimental scientific evidence for it?

Now this is hard: there are many theoretical assessments for the explanation of the natural phenomena at the extreme energy scales (from the subnuclear to the supercosmic), that possess a degree of clarity. But all of them are inspired by the vast collection of conciliatory data that scale by scale speak of Nature's works. This is so even for string theory. 

So the answer is still...nothing.

Following Bohr's complementarity I would spot that belief and proof are in some way complementary: if you believe you don't need proof, and (arguably) if you have proof you don't need to believe.(I would assign the hard-core string theorists who do not really care about experimental scientific evidence in the first category).

But Edge wants us to identify the equivalent(s) of the general theory of relativity in today's scientific thinking(s). Or a prediction of what are the big things in science that come at us unexpectedly. In my field, even frameworks that explain the world using extra dimensions of space (in extreme versions) are not unexpected. As a matter of fact we are preparing to discover or exclude them using the data. My hunch (and wish) is that in the laboratory we will be able to segment spacetime so finely that gravity will be studied and understood in a controlled environment, and that gravitational particle physics will be a new field.

Physicist, Perimeter Institute; Author, Time Reborn
Physicist, Perimeter Institute; Author, Three Roads to Quantum Gravity

I am convinced that quantum mechanics is not a final theory. I believe this because I have never encountered an interpretation of the present formulation of quantum mechanics that makes sense to me. I have studied most of them in depth and thought hard about them, and in the end I still can't make real sense of quantum theory as it stands. Among other issues, the measurement problem seems impossible to resolve without changing the physical theory.

Quantum mechanics must then be an approximate description of a more fundamental physical theory. There must then be hidden variables, which are averaged over to derive the approximate, probabilistic description which is quantum theory. We know from the experimental falsifications of the Bell inequalities that any theory which agrees with quantum mechanics on a range of experiments where it has been checked must be non-local. Quantum mechanics is non-local, as are all proposals for replacing it with something that makes more sense. So any additional hidden variables must be non-local. But I believe we can say more. I believe that the hidden variables represent relationships between the particles we do see, which are hidden because they are non-local and connect widely separated particles.

This fits in with another core belief of mine, which derives from general relativity, which is that the fundamental properties of physical entities are a set of relationships, which evolve dynamically. There are no intrinsic, non-relational properties, and there is no fixed background, such as Newtonian space and time, which exists just to give things properties.

One consequence of this is that the geometry of space and time is also only an approximate, emergent description, applicable only on scales too large to see the fundamental degrees of freedom. The fundamental relations are non-local with respect to the approximate notion of locality that emerges at the scale where it becomes sensible to talk about things located in a geometry.

Putting these together, we see that quantum uncertainty must be a residue of the resulting non-locality, which restricts our ability to predict the future of any small region of the universe. Hbar, the fundamental constant of quantum mechanics that measures the quantum uncertainty, is related to N, the number of degrees of freedom in the universe. A reasonable conjecture is that hbar is proportional to the inverse of the square root of N.

But how are we to describe physics, if it is not in terms of things moving in a fixed spacetime? Einstein struggled with this, and my only answer is the one he came to near the end of his life: fundamental physics must be discrete, and its description must be in terms of algebra and combinatorics.

Finally, what of time? I have been also unable to make sense of any of the proposals to do away with time as a fundamental aspect of our description of nature. So I believe in time, in the sense of causality. I also doubt that the "big bang" is the beginning of time, I strongly suspect that our history extends backwards before the big bang.

Finally, I believe that in the near future, we will be able to make predictions based on these ideas that will be tested in real experiments. 

biologist at the Port Erin Marine Station of the University of Liverpool (UK); Author, The Origins of Larvae
Biologist, University of Liverpool; Author, The Origins of Larvae

I believe I can explain the Cambrian explosion.

The Cambrian explosion refers to the first appearance in a relatively short space of geological time of a very wide assortment of animals more than 500 million years ago. I believe it came about through hybridization. 

Many well preserved Cambrian fossils occur in the Burgess shale, in the Canadian Rockies. These fossils include small and soft-bodied animals, several of which were planktonic but none were larvae. Compared with modern animals, some of them seem to have the front end of one animal and rear end of another. Modern larvae present a comparable set-up: larvae seem to be derived from animals in different groups from their corresponding adults. I have amassed a bookful of evidence that the basic forms of larvae did indeed originate as animals in other groups and that such forms were transferred by hybridization. Animals with larvae are "sequential chimeras", in which one body-form—the larva—is followed by another, distantly related form—the adult. I believe there were no Cambrian larvae, and Cambrian hybridizations produced "concurrent chimeras", in which two distantly related body-forms appeared together.

About 600 million years ago, shortly before the Cambrian, animals with tissues (metazoans) made their first appearance. I agree with Darwin that there were several different forms (Darwin suggested four or five), and I believe they resulted from hybridizations between different colonial protists. Protists are mostly single-celled, but colonial forms consist of many similar cells. All Cambrian animals were marine, and, like most modern marine animals, they shed their eggs and sperm into the water, where fertilization took place. Eggs of one species frequently encountered sperm of another, and there were only poorly developed mechanisms to prevent hybridization. Early animals had small genomes, leaving plenty of spare gene capacity. These factors led to many fruitful hybridizations, which resulted in concurrent chimeras. Not only did the original metazoans hybridize but the new animals resulting from these hybidizations also hybridized, and this produced the explosion in animal form.

The acquisition of larvae by hybridization came much later, when there was little spare genome capacity in recipes for single animals, and it is still going on. In the echinoderms (the group that includes sea-urchins and starfish) there is evidence that there were no larvae in either the Cambrian or the Ordovician (the following period), and this might well apply to other major groups. Acquiring parts, rather than larvae, by hybridization continued, I believe, throughout the Cambrian and Ordovician and probably later, but, as genomes became larger and filled most of the available space, later hybridizations led to smaller changes in adult form or to acquisitions of larvae. The gradual evolution of better mechanisms to prevent eggs being fertilized by foreign sperm resulted in fewer fruitful hybridizations, but occasional hybridizations still take place. 

Hybridogenesis, the generation of new organisms by hybridization, and symbiogenesis, the generation of new organisms by symbiosis, both involve fusion of lineages, whereas Darwinian "descent with modification" is entirely within separate lineages. These forms of evolution function in parallel, and "natural selection" works on the results.

I cannot prove that Cambrian animals had poorly developed specificity and spare gene capacity, but it makes sense.

science writer and commentator
Science writer and Commentator; Author, Pythagoras' Trousers

We all believe in something and science itself is premised on a whole set of beliefs. Above all, science is founded on the belief that things are comprehensible and that by the ingenuity of our minds and the probing of ever more subtle instruments we will ultimately come to know It All. But is the All inherently knowable? I believe, though I cannot prove it, that there will always be things we do not know—large things, small things, interesting things and important things.

If theoretical physics is any guide we might suppose that science is a march towards a finite goal. For the past few decades theoretical physicists have been searching for a so-called "Theory of Everything," what Nobel laureate Stephen Weinberg has also called a "Final Theory." This "ultimate" set of equations that would tie together all the fundamental forces which physicists recognize today—the four essential powers of gravity, electromagnetism, and the nuclear forces inside the cores of atoms. But such theory—if we are lucky enough to extract it from the current mass of competing contenders—would not tell us anything about how proteins form or how DNA came into being. Less still would it illuminate the machinations of a living cell, or the workings of the human mind. Frankly, a "theory of everything" would not even help us to understand how snowflakes form. 

In an age when we have discovered the origin of the universe and observed the warping of space and time it is shocking to hear that scientists do not understand something as "paltry" as the formation of ice crystals. But that is indeed the case.

Kenneth Libbrecht, chairman of the Cal tech physics department is a world expert on ice crystal formation, a hobby project he took on more than twenty years ago precisely because as he puts it "there are six billion people on this planet, and I thought that at least one of us should understand how snow crystals form." After two decades of meticulous experimentation inside specially constructed pressurized chambers Libbrecht believes he has made some headway in understanding how ice crystallizes at the edge of the quasi-liquid layer which surrounds all ice structures. He calls his theory "structure dependent attachment kinetics," but he is quick to point out that this is far from the ultimate answer. The transition from water to ice is a mysteriously complex process that has engaged minds as brilliant as Johannes Kepler and Michael Faraday. Libbrecht hopes he can add the small next step in our knowledge of this wondrous substance that is so central to life itself. 

Studying ice crystals is Libbrecht's hobby—in his "day job" he is one of the hundreds of physicists who are working on the LIGO detector which is designed to detect gravitational waves that are believed to emanate from black holes and other massive cosmological entities. Gravity waves have been predicted by the general theory of relativity, and hence physicists believe they must exist. Here the matter of belief has literally bought into being a an extremely expensive machine. Any successful theory of everything will have to account for gravity, the most mysterious of all the forces and the one physicists least understand. Like the other three forces, physicists believe gravity must ultimately manifest itself in both wave and particle forms. LIGO is designed to detect such waves, if indeed they do exist.

Some years ago the science writer John Horgan wrote a marvelously provocative book in which he suggested that science was coming to an end, all the major theoretical edifices now supposedly being in place. Horgan was right in one sense, for high-energy physics may be on the verge of achieving its final unification. But in so many other areas, science is just beginning. Only now are we acquiring the scientific tools and techniques to begin to investigate how our atmosphere works, how ecological systems function, how genes create proteins, how cells evolve, and how brains work. The very success of "fundamental science" has opened doors undreamed of by earlier generations and in many ways it seems there is more than ever that we do not know. At a time when journals tout theories about how to create entire universes it is easy to imagine that science has grasped the whole of reality. In truth our ignorance is vast—and personally I believe it will always be so. 

Rather than pretend we will soon know it all, I suggest we might adopt instead the attitude of the great fifteenth century champion of science, Cardinal Nicholas of Cusa. Cusa titled his major work On Learned Ignorance. A complex and poetic fusion of mathematics, scientific speculation and Catholic theology, Cusa puts forward in this book the view that we can never —even in principle—know everything. Only God can do that. We mortals, confined within the world itself can never see it whole, from the outside as it were. But while we cannot know it All, Cusa insists we can know a great deal and that science and mathematics will take our knowledge forward. Our ignorance then can be ever more learned. Not omniscience then, but an ever more subtle and insightful unknowing is the goal that Cusa advocated. In the humble snowflakes Ken Libbrecht studies we have the perfect metaphor for such a view—though they melt on your tongue, each tiny crystal of ice encapsulates a universe whose basic rules we have barely begun to unravel.

A leading scientist of the 21st century for Genomic Sciences; Co-Founder, Chairman, Synthetic Genomics, Inc.; Founder, J. Craig Venter Institute; Author, A Life Decoded
Genomics Researcher; Founder & President, J. Craig Venter Science Foundation

Life is ubiquitous throughout the universe. Life on our planet earth most likely is the result of a panspermic event (a notion popularized by the late Francis Crick).

DNA, RNA and carbon based life will be found wherever we find water and look with the right tools. Whether we can prove life happens, depends on our ability to improve remote sensing and to visit faraway systems. This will also depend on whether we survive as a species for a sufficient period of time. As we have seen recently in the shotgun sequencing of the Sargasso Sea, when we look for life here on Earth with new tools of DNA sequencing we find life in abundance in the microbial world. In sequencing the genetic code of organisms that survive in the extremes of zero degrees C to well over boiling water temperatures we begin to understand the breadth of life, including life that can thrive in extremes of caustic conditions of strong acids to basic pH's that would rapidly dissolve human skin. Possible indicators of panspermia are the organisms such as Deinococcus radiodurans, which can survive millions of RADs of ionizing radiation and complete desiccation for years or perhaps millennia. These microbes can repair any DNA damage within hours of being reintroduced into an aqueous environment.

Our human centric view of life is clearly unwarranted. From the millions of genes that we have just discovered in environmental organisms over the past months we learn that a finite number of themes are used over and over again and could have easily evolved from a few microbes arriving on a meteor or on intergalactic dust. Panspermia is how life is spreads throughout the universe and we are contributing to it from earth by launching billions of microbes into space.

Archaeologist, Professor of the Prehistory of Humanity, University of Vienna; Author, The Artificial Ape
Archaeologist, University of Bradford; Author, The Buried Soul

"All your life you live so close to the truth, it becomes a permanent blur in the corner of your eye, and when something nudges it into outline it is like being ambushed by a grotesque" wrote Tom Stoppard in Rosencrantz and Guildenstern are Dead. Something I believe is true even though I cannot prove it, is that both cannibalism and slavery were prevalent in human prehistory. Neither belief commands specialist academic consensus and each phenomenon remains highly controversial, their empirical "signatures" in the archaeological record being ambiguous and fugitive.

Truth and belief are uncomfortable words in scholarship. It is possible to define as true only those things that can be proved by certain agreed criteria. In general, science does not believe in truth or, more precisely, science does not believe in belief. Understanding is understood as the best fit to the data under the current limits (both instrumental and philosophical) of observation. If science fetishized truth, it would be religion, which it is not. However, it is clear that under the conditions that Thomas Kuhn designated as " normal science" (as opposed to the intellectual ferment of paradigm shifts) most scholars are involved in supporting what is, in effect, a religion. Their best guesses become fossilized as a status quo, and the status quo becomes an item of faith. So when a scientist tells you that "the truth is . . .", it is time to walk away. Better to find a priest.

Until recently, most archaeologists would be inclined to say that the truths about cannibalism and about slavery are that each has been sharply historically limited and that each is a more or less aberrant cultural phenomenon. The reason for such a belief is that it is only in a small number of cases that either thing be proved beyond reasonable doubt. But I see the problem in the starting point.

If we shift our background expectations and say that coercing a living person to do one's bidding is perhaps the very first form of property ownership ("the slavery latent in the family" to use Marx and Engels' telling phrase), and that eating the dead (as very many wild vertebrates do) makes sense in nutritional and competitive terms, then the archaeologist's duty is to empirically establish those times and places where slavery and cannibalism had ceased to exist. The only reason we have hitherto insisted on proof-positive rather than proof-negative in relation to these phenomena is that both seem grotesque to us now, and we have rather a high opinion of our natural civility. This is the most interesting point, and the focus of my attention is how culturally-elaborated mechanisms of restraint and inter-personal respect emerged and allowed such refined scruples.

psychologist at Boston College
Psychologist, Boston College; Author, Gifted Children

Sometimes our folk theories are correct: Parents do shape their children.

According to our folk theories of child development, parents are a major and inescapable influence on their children. Most people believe that how parents treat their children, as well as the values parents impart, leaves a strong and indelible imprint. Yet some psychologists have countered this view and have pointed to the finding that on paper and pencil personality tests, parents and children (especially parents and their adopted children) are often not mirrors of one another. Psychologists have not yet proven to skeptics that parents have a strong influence on their children, but I am convinced that we will be able to demonstrate this.

To begin with, producing children whose personality mirrors ones own is hardly the only way for parents to influence their children. We should not expect children to mirror their parents' personalities since they may often develop personalities in reaction to their parents. If you react against something, that something is having an influence on you. A depressed mother may engender a solicitous child. An impulsive parent may engender a careful child intent on not repeating the parent's errors.

Another problem with only using personality tests to examine parental influence is that these tests ignore political, social, and moral values and aesthetic tastes. I believe that children end up with much of their parents' values and tastes. We know that one of the best predictors of how people vote is how their parents vote. Parental values such as generosity, ambition, materialism, anti-materialism, etc have powerful effects on children. True, children may react against their parents' values. Materialistic parents have bred hippie children. But how many of these children eventually shed their hippie clothing and go to Wall Street? All too many.

If parents had no influence on their children, what is it that keeps psychoanalysts in business? Some children hate their parents. Some feel rage at their parents. Some feel their parents make them feel guilty. Some feel damaged by their parents. Some feel they are carrying on their parents' traditions. Some feel they owe their character strength to their parents. I fervently doubt that these feelings are merely epiphenomenal.

Judith Rich Harris, in The Nurture Assumption, took the position that parents have essentially no influence on their children besides passing on their genes and choosing their children's peer group. Steve Pinker said that the publication of this book was a landmark event in the history of psychology. I disagree with Harris' extreme claims and Pinker's endorsement.

To demonstrate parents' effects on their children, we will need better measures than quantitative short answer paper and pencil personality tests, and we will need to recognize that parents may influence their children to become like them or to become unlike them. One way to start is to develop a set of predictions about how parents shape their children (either to become like or unlike them), interview people about how they believe they have been shaped by their parents, and look for whether the patterns found fit the predictions. A stronger way is to look at adult adopted children, after the tumultuous adolescent years, and look at the extent to which these children either share their adoptive parents' values or have reacted against those values. Either way (sharing or reacting against), there is a powerful parental influence. The way to disprove my claim would be to show no systematic positive or negative relationships between parents and adoptive children. The belief that parents shape their children is part of our folk theory. Sometimes our folk theories are correct.

Professor of Computer Science at Stanford University
Computer Scientist; Artificial Intelligence Pioneer, Stanford University

I think, as did Gödel, that the continuum hypothesis is false. No-one will ever prove it false from the presently accepted axioms of set theory. Chris Freiling's proposed new (1986) axioms prove it false, but they are not regarded as intuitive.

I think human-level artificial intelligence will be achieved.

Media Analyst; Documentary Writer; Author, Present Shock
Media Analyst; Documentary Writer; Author, Media Virus

I can't prove it more than anecdotally, but I believe evolution has purpose and direction. It appears obvious, yet absolutely unconfirmable, that matter is groping towards complexity. While the laws of nature—and time itself—require objects and life forms attain durability and sustainability for survival, it seems to me more a means to an end than an end in itself.

Theology goes a long way towards imbuing substance and processes with meaning—describing life as "matter reaching towards divinity," or as the process through which divinity calls matter back up into itself—but theologians repeatedly make the mistake of ascribing this sense of purpose to history rather than the future. This is only natural, since the narrative structures we use to understand our world tend to have beginnings, middles, and ends. In order to experience the pay-off at the end of the story, we need to see it as somehow built-in to the original intention of events.

It's also hard for people to contend with the great probability that we are simply over-advanced fungi and bacteria, hurling through a galaxy in cold and meaningless space. Our existence may be unintentional, meaningless and purposeless; but that doesn't preclude meaning or purpose from emerging as a result of our interaction and collaboration. Meaning may not be a precondition for humanity, but rather a byproduct of it.

That's why it's so important to recognize that evolution, at its best, is a team sport. As Darwin's later, lesser-known, but more important works contended, survival of the fittest is not a law applied to individuals, but to groups. Just as it is now postulated that mosquitoes cause their victims to itch and sweat nervously so that other mosquitoes can more easily find the target, most great leaps forward in human evolution—from the formation of clans to the building of cities—are feats of collaborative effort. Better rates of survival are as much a happy side effect of good collaboration as their purpose.

If we could stop relating to meaning and purpose as artifacts of some divine creative act, and see them instead as the yield of our own creative future, they become goals, intentions, and processes very much in reach—rather than the shadows of childlike, superstitious mythology

The proof is impossible, since it is an unfolding one. Like reaching a horizon, arrival merely necessitates more travel.

Novelist; Author, Sweet Tooth; Solar; On Chesil Beach; Amsterdam
Novelist; Author, Saturday

What I believe but cannot prove is that no part of my consciousness will survive my death. I exclude the fact that I will linger, fadingly, in the thoughts of others, or that aspects of my consciousness will survive in writing, or in the positioning of a planted tree or a dent in my old car. I suspect that many contributors to Edge will take this premise as a given—true but not significant. However, it divides the world crucially, and much damage has been done to thought as well as to persons, by those who are certain that there is a life, a better, more important life, elsewhere. That this span is brief, that consciousness is an accidental gift of blind processes, makes our existence all the more precious and our responsibilities for it all the more profound.

Professor of Psychiatry, UM Medical School; Professor of Psychology, University of Michigan; Co-author, Why We Get Sick
Psychiatrist, University of Michigan; Coauthor, Why We Get Sick

I can't prove it, but I am pretty sure that people gain a selective advantage from believing in things they can't prove. I am dead serious about this. People who are sometimes consumed by false beliefs do better than those who insist on evidence before they believe and act. People who are sometimes swept away by emotions do better in life than those who calculate every move. These advantages have, I believe, shaped mental capacities for intense emotion and passionate beliefs because they give a selective advantage in certain situations.

I am not advocating for irrationality or extreme emotionality. Many, perhaps even most problems of individuals and groups arise from actions based on passion. The Greek initiators and Enlightenment implementers recognized correctly that the world would be better off if reason displaced superstition and crude emotion. I have no interest in going back on that road and fundamentalism remains a severe threat to enlightened civilization. I am arguing, however, that if we want to understand these tendencies we need to quit dismissing them as defects and start considering how they came to exist. 

I came to this belief from seeing psychiatric patients while studying game theory and evolutionary biology. Many patients are consumed by fears, sadness, and other emotions they find painful and senseless. Others are crippled by grandiose fantasies or bizarre beliefs. On the other side are those with obsessive compulsive personality. They do not have obsessive compulsive disorder; they do not wash and count all day. They have obsessive compulsive personality characterized by hyper-rationality. They are mystified by other people's emotional outbursts. They do their duty and expect others will too. They are often disappointed in this, giving rise to frequent resentment if not anger. They trade favors according to the rules, and they can't fathom genuine generosity or spiteful hatred.

People who lack passions suffer several disadvantages. When social life results in situations that can be mapped onto game theory, regular predictable behavior is a strategy inferior to allocating actions randomly among the options. The angry person who might seek spiteful revenge is a force to be reckoned with, while a sensible opponent can be easily dealt with. The passionate lover sweeps away a superior but all too practical offer of marriage.

It is harder to explain the disadvantages suffered by people who lack a capacity for faith, but consider the outcomes for those who wait for proof before acting, compared to the those who act on confident conviction. The great things in life are done by people who go ahead when it seems senseless to others. Usually they fail, but sometimes they succeed.

Like nearly every other trait, tendencies for passionate emotions and irrational convictions are most advantageous in some middle range. The optimum for modern life seems to me to be quite a ways towards the rational side of the median, but there are advantages and disadvantages at every point along the spectrum. Making human life better requires that we understand these capacities, and to do that we must seek their origins and functions. I cannot prove this is true, but I believe it is. This belief spurs my search for evidence which will either strengthen my conviction or, if I can discipline my mind sufficiently, convince me that it is false.

Sterling Professor of Mathematical Sciences, Yale University; IBM Fellow Emeritus (Physics) at the IBM; author, The Fractalist; Memoir of a Scientific Maverick
Mathematician, Yale University; Author, The Fractal Geometry of Nature

Wandering through the frontiers of the sciences, and the arts, I have always trusted the eye while leaving aside the issues that elude it. It can mislead—of course—therefore I check endlessly and never rush to print. 

Meanwhile, for over fifty years, I have watched as some disciplines exhaust the "top down" problems they know how to tackle. So they wander around seeking totally new patterns in a dark and deep mess, where an unlit lamp is of little help.

But the eye can continually be trained and, long ago, I have vowed to follow it, therefore work "from the bottom up." Like the Antaeus of Greek myth, I gather strength and persist by often touching the earth.

A few of the truths the eye told me have been disproven. Let it be. Others have been confirmed by enormous and fruitful effort, and then blossomed, one being the four thirds conjecture in Brownian motion. Many others remain, one being the MLC conjecture about the Mandelbrot set, in which I believe for no other reason than trust in the eye.

Classical Scholar, University Professor, Georgetown University; Author, The Ruin of the Roman Empire; Webmaster, St. Augustine's Website
Classicist; Cultural Historian; Provost, Georgetown University; Author, Avatars of the Word

What do I believe is true even though I cannot prove it? This question has a double edge and needs two answers.

First, and most simply: "everything". On a strict Popperian reading, all the things I "know" are only propositions that I have not yet falsified. They are best estimates, hypotheses that, so far, make sense of all the data that I possess. I cannot prove that my parents were married on a certain day in a certain year, but I claim to "know" that date quite confidently. Sure, there are documents, but in fact in their case there are different documents that present two different dates, and I recall the story my mother told to explain that and I believe it, but I cannot "prove" that I am right. I also know Newton's Laws and indeed believe them, but I also now know their limitations and imprecisions and suspect that more surprises may lurk in the future.

But that's a generic answer and not much in the forward-looking and optimistic spirit that characterizes Edge. So let me propose this challenge to practitioners of my own historical craft. I believe that there are in principle better descriptions and explanations for the development and sequence of human affairs than human historians are capable of providing. We draw our data mainly from witnesses who share our scale of being, our mortality, and for that matter our viewpoint. And so we explain history in terms of human choices and the behavior of organized social units. The rise of Christianity or the Norman Conquest seem to us to be events we can explain and we explain them in human-scale terms. But it cannot be excluded or disproved that events can be better explained on a much larger time scale or a much smaller scale of behavior. An outright materialist could argue that all my acts, from the day of my birth, have been a determined result of genetics and environment. It was fashionable a generation ago to argue a Freudian grounding for Luther's revolt, but in principle it could as easily be true and, if we could know it, more persuasive to demonstrate that his acts were determined a the molecular and submolecular level.

The problem with such a notion is, of course, that we are very far from being able to outline such a theory, much less make it persuasive, much less make it something that another human being could comprehend. Understanding even one other person's life at such microscopic detail would take much more than one lifetime.

So what is to be done? Of course historians will constantly struggle to improve their techniques and tools. The advance of dendrochronology (dating wood by the tree rings, and consequently dating buildings and other artifacts far more accurately than ever before) can stand as one example of the way in which technological advance can tell us things we never knew before. But we will also continue to write and to read stories in the old style, because stories are the way human beings most naturally make sense of their world. An awareness of the powerful possibility of whole other orders of possible description and explanation, however, should at least teach us some humility and give us some thoughtful pause when we are tempted to insist too strongly on one version of history—the one we happen to be persuaded is true. Even a Popperian can see that this kind of intuition can have beneficial effect.

Mathematician, Computer Scientist; CyberPunk Pioneer; Novelist; Author, Lifebox, the Seashell, and the Soul: What Gnarly Computation Taught Me About Ultimate Reality, the Meaning of Life, and How to be Happy
Mathematician, Computer Scientist; CyberPunk Pioneer; Novelist; Author, Infinity and the Mind

Reality Is A Novel.

I'd like to propose a modified Many Universes theory. Rather than saying every possible universe exists, I'd say, rather, that there is a sequence of possible universes, akin to the drafts of a novel.

We're living in a draft version of the universe—and there is no final version. The revisions never stop.

From time to time it's possible to be aware of this. In particular, when you relax and stop naming things and forming opinions, your consciousness spreads out across several drafts of the universe. Things don't need to be particularly one way or the other until you pin them down.

Each draft, each spacetime, each sheet of reality is itself rigorously deterministic; there really is no underlying randomness in the world. Instead we have a great web of synchronistic entanglements, with causes and effects flowing forward and backwards through time. The start of a novel matches its ending; the past matches the future. Changing one thing changes everything. If we fully know everything about the Now moment, we know the entire past and future.

With this in mind, explaining an given draft of the universe becomes a matter of explaining the contents of a single Now moment of that draft. This in turn means that we can view the evolution of the successive drafts as an evolution of different versions of a particular Now moment. As Scarlett's climactic scene with Rhett is repeatedly rewritten, all the rest of Gone With The Wind changes to match.

And this evolution, too, can be deterministic. We can figure we think of there as being two distinct deterministic rules, a Physics Rule and a Metaphysics Rule. The Physics Rule consists of time-reversible laws that grow the Now moment upwards and downwards to fill out the entire past and future of spacetime. And we invoke the Metaphysics Rule to account for the contents of the Now moment. The Metaphysics Rule is deterministic but not reversible; it grows sideways across a dimension that we might call paratime, turning some simple seed into the space-filling pattern found in the Now.

The Metaphysics rule is...what? One possibility is that it's something quite simple, perhaps as simple as an eight-bit cellular automaton rule generating complex-looking patterns out of pure computation. Or perhaps the Metaphysics rule is like the mind of an author creating a novel, searching out the best word to write next, somehow peering into alternate realities. Or, yet again, the big Metaphysics rule in the sky could be the One cosmic mind, the Big Aha, the eternal secret, living in the spaces between your thoughts.

Evolutionary Biologist; Professor of Anthropology and Biological Sciences, Rutgers University; Author, The Folly of Fools
Evolutionary biologist, Rutgers University; Author, Natural Selection and Social Theory

Think true, cannot prove. 

I believe that deceit and self deception play a disproportinate role in human-generated disasters, including misguided wars, international affairs more gnerally, the collapse of civilizations, and state affairs, including disastrous social, political and economic policies and miscarriages of justice.

I believe deceit and self deception play an important role in the relative
underdevelopment of the social sciences.

I believe that processes of self deception are important in limiting the
achievement of individuals.

climatologist, is a professor in the Department of Biological Sciences
Biologist; Climatologist, Stanford University; Author, Laboratory Earth

I believe that global warming is both a real phenomenon and at least partially a result of human activities such as dumping greenhouse gases in the atmosphere. In fact I can "prove it"—or can I?—that is the real question.

What is "proof"? In the strict old fashioned frequentist statistical belief system data is direct observations of the hypothesized phenomena—temperature increases in my case—and when you get enough of it to produce frequency distributions you can assign objective probabilities to cause and effect hypotheses. But what if the events cannot be precisely measured, or worse, apply to future events like the warming of the late 21st century? Then a frequentist interpretation of " proof" is impossible in principle before the fact, and we instead become subjectivists—Bayesian updaters as some statisticians like to refer to it. In this case we use frequency data and all other data relevant to components of our analysis to form a "prior"—a belief about likelihood of an event or process. Then as we learn more we update our belief—an "a posteriori probability" as the Bayesians call it—or simply a revised prior.

It is my strong belief that there is an overwhelming amount of evidence to form a subjective prior with high confidence that the earth's surface has warmed over the past century about 0.7 deg C or so and that at least half of the more recent warming is traceable to human pressures. Is this " proof" of anthropogenic (i.e., we did it) warming? Not in the strict sense of a criminal trial with "beyond a reasonable doubt" criterion—say a 99% objective probability. But in the sense of a civil proceeding, where " preponderance of evidence" is the standard and a likelihood much greater than 50% is adequate to have a case, then global warming is indeed already " proved". So as a frequentist I concede I believe it is real without full "proof", but as a subjectivist, my reading of the many lines of evidence puts global warming well over the minimum thresholds of belief to assert it is already "proved".

Neuroscientist; Collège de France, Paris; Author, The Number Sense; Reading In the Brain
Cognitive Neuropsychology Researcher, Institut National de la Santé, Paris; Author, The Number Sense

I believe (but cannot prove) that we vastly underestimate the differences that set the human brain apart from the brains of other primates.

Certainly, no one can deny that there are important similarities in the overall layout of the human brain and, say, the macaque monkey brain. Our primary sensory and motor cortices are organized in similar ways. Even in higher brain areas, homologies can be found. In the parietal lobe, using brain-imaging methods, my lab has observed plausible human counterparts to several areas of the macaque brain, involved in eye movement, hand gestures, and even number processing.

Yet I fear that those early successes in drawing human-monkey homologies tend to mask other massive differences. If we compare the primary visual areas of macaques and humans, there is already a two-fold difference in surface area, but in parietal and frontal areas, a twenty-to fifty-fold increase is found. Even such a massive distortion may not suffice to "align" the macaque and human brain. Many of us suspect that, in regions such as the prefrontal and inferior parietal cortices, the changes are so dramatic that they may amount to the addition of new brain areas.

At a more microscopic level, it is already known that there is a new type of neuron which is found in the anterior cingulate region of humans and great apes, but not in other primates. These "spindle cells" send connections throughout the cortex, and thus contribute to a massive increase in long-distance connectivity in the human brain. Indeed, the change in relative white matter volume is perhaps what is most dramatic about the human brain.

I believe that these surface and connectivity changes, although they are in many cases quantitative, have brought about a qualitative revolution in brain function:

Breaking the brain's modularity.

Jean-Pierre Changeux and I have proposed that the increased connectivity of the human brain gives access to a new mode of brain function, characterized by a very flexible communication between distant brain areas. We may possess roughly the same list of specialized cerebral processors as our primate ancestors. However, I speculate that what might be unique about the human brain is its capacity to access the information inside each processor, and make it available to almost any other processor through long-distance connections. I believe that we humans have a much more developed conscious workspace—a set of brain areas that can fluidly exchange signals, thus allowing us to internally manipulate information and to perform new mental syntheses. Using the workspace's long-distance connections, we can mobilize, in a top-down manner, essentially any brain area and bring it into consciousness.

Spontaneous activity and the autonomy of consciousness.

Once the internal connectivity of a system exceeds a threshold, it begins to be dominated by self-sustained, reverberating states of activity. I believe that the human workspace system has passed this threshold, and has gained a considerable autonomy relative to the outside world. The human brain is much less at the mercy of signals from the outside world. Its activity never ceases to reverberate from area to area, thus generating a highly structured spontaneous flow of thoughts that we project on the outside world.

Of course, spontaneous brain activity is present in all species, but if I am correct we will discover that it is both more evident and more structured in the human brain, at least in higher cortical areas where "workspace" neurons with long-distance axons are denser. Furthermore, if human brain activity can be detached from outside stimulation, we will need to find new paradigms to study it, because bombarding the human brain with stimuli, as we do in most brain-imaging experiments, will not suffice. There is already some evidence for this statement: by directly comparing fMRI activations evoked by the same visual stimuli in humans and macaques, Guy Orban and his colleagues in Leuven have found that prefrontal cortex activity is five times larger in macaques than in humans. In their own words, "there may be more volitional control over visual processing in humans than in monkeys".

The profound influence of culture on the human brain.

The human species is also unique in its ability to expand its functionality by inventing new cultural tools. Writing, arithmetic, science, are all very recent inventions—our brains did not have time to evolve for them, but I speculate that they were made possible because we can mobilize our old areas in novel ways. When we learn to read, we "recycle" a specific region of our visual system, which has become known as the "visual word form area", for the purpose of recognizing strings of letters and connecting them to language areas. When we learn Arabic numerals, likewise, we build a circuit to quickly convert those shapes into quantities, a fast connection from bilateral visual areas to the parietal quantity area. Even an invention as elementary as finger counting changes dramatically our cognitive abilities: Amazonian people that have not invented counting are unable to make exact calculations as simple as 6-2.

Crucially, this "cultural recycling" implies that whenever we look at a human brain, the functional architecture that we see results from a complex mixture of biological and cultural constraints. Education is likely to greatly increase the gap between the human brain and that of our primate cousins. Virtually all human brain imaging experiments today are performed on highly literate volunteers—and therefore, presumably, highly transformed brains. To better understand the differences between the human brain and the monkey brain, we will need to invent new methods, both to decipher the organization of the baby brain prior to education, and to study of how it changes with education

Author, Machines Who Think, The Universal Machine, Bounded Rationality, This Could Be Important; Coauthor (with Edward Feigenbaum), The Fifth Generation
Writer; Author, Machines Who Think

Although I can't prove it, I believe that thanks to new kinds of social modeling, that take into account individual motives as well as group goals, we will soon grasp in a deep way how collective human behavior works, whether it's action by small groups or by nations. Any predictive power this understanding has will be useful, especially with regard to unexpected outcomes and even unintended consequences. But it will not be infallible, because the complexity of such behavior makes exact prediction impossible.

biologist and author
Biologist, London; Author of The Presence of the Past

I believe, but cannot prove, that memory is inherent in nature. Most of the so-called laws of nature are more like habits.

There is no need to suppose that all the laws of nature sprang into being fully formed at the moment of the Big Bang, like a kind of cosmic Napoleonic code, or that they exist in a metaphysical realm beyond time and space.

Before the general acceptance of the Big Bang theory in the 1960s, eternal laws seemed to make sense. The universe itself was thought to be eternal and evolution was confined to the biological realm. But we now live in a radically evolutionary universe.

If we want to stick to the idea of natural laws, we could say that as nature itself evolves, the laws of nature also evolve, just as human laws evolve over time. But then how would natural laws be remembered or enforced? The law metaphor is embarrassingly anthropomorphic. Habits are less human-centred. Many kinds of organisms have habits, but only humans have laws.

Habits are subject to natural selection; and the more often they are repeated, the more probable they become, other things being equal. Animals inherit the successful habits of their species as instincts. We inherit bodily, emotional, mental and cultural habits, including the habits of our languages.

The habits of nature depend on non-local similarity reinforcement. Through a kind of resonance, the patterns of activity in self-organizing systems are influenced by similar patterns in the past, giving each species and each kind of self-organizing system a collective memory.

Is this just a vague philosophical idea? I believe it can be formulated as a testable scientific hypothesis.

My interest in evolutionary habits arose when I was engaged in research in developmental biology, and was reinforced by reading Charles Darwin, for whom the habits of organisms were of central importance. As Francis Huxley has pointed out, Darwin's most famous book could more appropriately have been entitled The Origin of Habits.

Over the course of fifteen years of research on plant development, I came to the conclusion that for understanding the development of plants, their morphogenesis, genes and gene products are not enough. Morphogenesis also depends on organizing fields. The same arguments apply to the development of animals. Since the 1920s many developmental biologists have proposed that biological organization depends on fields, variously called biological fields, or developmental fields, or positional fields, or morphogenetic fields.

All cells come from other cells, and all cells inherit fields of organization. Genes are part of this organization. They play an essential role. But they do not explain the organization itself. Why not?

Thanks to molecular biology, we know what genes do. They enable organisms to make particular proteins. Other genes are involved in the control of protein synthesis. Identifiable genes are switched on and particular proteins made at the beginning of new developmental processes. Some of these developmental switch genes, like the Hox genes in fruit flies, worms, fish and mammals, are very similar. In evolutionary terms, they are highly conserved. But switching on genes such as these cannot in itself determine form, otherwise fruit flies would not look different from us.

Many organisms live as free cells, including many yeasts, bacteria and amoebas. Some form complex mineral skeletons, as in diatoms and radiolarians, spectacularly pictured in the nineteenth century by Ernst Haeckel. Just making the right proteins at the right times cannot explain such structures without many other forces coming into play, including the organizing activity of cell membranes and microtubules.

Most developmental biologists accept the need for a holistic or integrative conception of living organization. Otherwise biology will go on floundering, even drowning, in oceans of data, as yet more genomes are sequenced, genes are cloned and proteins are characterized.

I suspect that morphogenetic fields work by imposing patterns on the otherwise random or indeterminate patterns of activity. For example they cause microtubules to crystallize in one part of the cell rather than another, even though the subunits from which they are made are present throughout the cell.

Morphogenetic fields are not fixed forever, but evolve. The fields of Afghan hounds and poodles have become different from those of their common ancestors, wolves. How are these fields inherited? I believe, but cannot prove, that they are transmitted by a kind of non-local resonance, and I have suggested the term morphic resonance for this process.

The fields organizing the activity of the nervous system are likewise inherited through morphic resonance, conveying a collective, instinctive memory. The resonance of a brain with its own past states also helps to explain the memories of individual animals and humans.

Social groups are likewise organized by fields, as in schools of fish and flocks of birds. Human societies have memories that are transmitted through the culture of the group, and are most explicitly communicated through the ritual re-enactment of a founding story or myth, as in the Jewish Passover celebration, the Christian Holy Communion and the American thanksgiving dinner, through which the past become present through a kind of resonance with those who have performed the same rituals before.

Others may prefer to dispense with the idea of fields and explain the evolution of organization in some other way, perhaps using more general terms like "emergent systems properties". But whatever the details of the models, I believe that the natural selection of habits will play an essential part in any integrated theory of evolution, including not just biological evolution, but also physical, chemical, cosmic, social, mental and cultural evolution.

Chair of Reproductive Biology, Director Scottish Centre for Regenerative Medicine, University of Edinburgh; Author, After Dolly
Biologist; Cloning Researcher; Roslin Institute, Edinburgh; Coauthor, The Second Creation

I believe that it is possible to change adult cells from one phenotype to another.

The birth of Dolly provided the insight behind this belief. She was the first adult cloned from another adult, of any species. Previously biologists had believed that the mechanisms that direct the formation of all of the different tissues that make up an adult were so complex and so rigidly fixed that they could not be reversed. Her birth demonstrated that the mechanisms that were active in the nucleus transferred from the mammary epithelial cell could be reversed by unknown factors in the recipient unfertilised egg.

We take for-granted the process by which the single cell embryo at fertilisation gives rise to all of the many tissues of an adult. As almost all of those cells have the same genetic information, the changes must be brought about by sequential differences in function of the genes. An impression is beginning to emerge of the factors that bring about these sequential changes, although much more remains to be learned. In particular, very little is known of the hierarchy of influence of the several regulatory factors.

I believe that a greater understanding of these mechanisms will allow us to cause cells from one tissue to form another different tissue. We have long been accustomed to the idea that cells are influenced by their external environment and use specific methods of tissue culture to control their function in the laboratory. The new research introduces an additional dimension. We will learn how to increase the activity of the intracellular factors to achieve our aims. This may be by direct introduction of the proteins, use of small molecule drugs to modulate expression of regulatory genes or transient expression of those key genes. We have much to learn about the optimal approach to „transdifferentiation¾. Is it necessary to reverse the process of differentiation to an early stage in the same pathway? Or is it possible to achieve change directly from one path to another? The answer may vary from one tissue to another.

The medical implications will be profound. Cells of specific tissues will be available from patients either for research to understand genetic differences or for their therapy, This is not to suggest that we cease research on embryo stem cells because knowledge from their use will be essential to develop the new approaches that I envisage. Conversely, understanding of the mechanisms of reprogramming cells will create important new opportunities in the use of embryo stem cells. As many options as possible should be available to the researcher and clinician.

It is my belief that, ultimately, this approach to tissue formation will be the greatest inheritance of the Dolly experiment. The ramifications are far wider than those that involve the production of cloned offspring.

professor of biology at the Schumacher College
Biologist, Schumacher College, Devon, UK; Author, How The Leopard Changed Its Spots

Nature Is Culture.

I believe that nature and culture can now be understood as one unified process, not two distinct domains separated by some property of humans such as written or spoken language, consciousness, or ethics. Although there is no proof of this, and no consensus in the scientific community or in the humanities, the revelations of the past few years provide a foundation for both empirical and conceptual work that I believe will lead to a coherent, unified perspective on the process in which we and nature are engaged. This is not a take-over of the humanities by science, but a genuine fusion of the two based on clear articulations of basic concepts such as meaning and wholeness in natural and cultural processes, with implications for scientific studies, their applications in technology and their expression in the arts.

For me this vision has arisen primarily through developments in biology, which occupies the middle ground between culture and the physical world. The key conceptual changes have arisen from complexity theory through detailed studies of the networks of interactions between components within organisms, and between them in ecosystems. When the genome projects made it clear that we are unable to make sense of the information in DNA, attention necessarily shifted to understanding how organisms use this in making themselves with forms that allow them to survive and reproduce in particular habitats. The focus shifted from the hereditary material to its organised context, the living cell, so that organisms as agencies with a distinctive kind of organisation returned to the biological foreground.

Examination of the self-referential networks that regulate gene activities in organisms, that carry out the diverse functions and constructions within cells through protein-protein interactions (the proteome), and the sequences of metabolic transformations that make up the metabolome, have revealed that they all have distinctive properties of self-similar, fractal structure governed by power-law relationships. These properties are similar to the structure of languages, which are also self-referential networks described by power-laws, as discovered years ago by G.K. Zipf. A conclusion is that organisms use proto-languages to make sense of both their inherited history (written in DNA and its molecular modifications) and their external contexts (the environment) in the process of making themselves as functional agencies. Organisms thus become participants in cultures with histories that have meaning, expressed in the forms (morphologies and behaviours) distinctive to their species. This is of course embodied or tacit meaning, which cognitive scientists now recognise as primary in human culture also.

Understanding species as cultures that have experienced 3.7 billion years of adaptive evolution on earth makes it clear that they are repositories of meaningful knowledge and experience about effective living that we urgently need to learn about in human culture. Here is a source of deep wisdom about living in participation with others that is energy and resource efficient, that recycles everything, produces forms that are simultaneously functional and beautiful, and is continuously innovative and creative. We can now proceed with a holistic science that is unified with the arts and humanities and has at its foundation the principles that arise from a naturalistic ethic based on an extended science that includes qualities as well as quantities within the domain of knowledge.

There is plenty of work to do in articulating this unified perspective, from detailed empirical studies of the ways in which organisms achieve their states of coherence and adaptability to the application of these principles in the organic design of all human artefacts, from energy-generating devices and communication systems to cars and factories. The goal is to make human culture as integrated with natural process as the rest of the living realm so that we enhance the quality of the planet instead of degrading it. This will require a rethinking of evolution in terms of the intrinsic agency with meaning that is embodied in the life cycles of different species, understood as natural cultures. Integrating biology and culture with physical principles will be something of a challenge, but there are already many indications of how this can be achieved, without losing the thread of language and meaning that runs through living nature. The emphasis on wholeness that lies at the heart of quantum mechanics and its extensions in quantum gravity, together with the subtle order revealed as quantum coherence, is already stimulating a rethinking of the nature of wholeness, coherence and robust adaptability in organisms as well as quality of life in cultures. Furthermore, the self-similar, fractal patterns that arise in physical systems during phase transitions, when new order is coming into being, have the same characteristics as the patterns observed in organismic and cultural networks involved in generating order and meaning. The unified vision of a creative and meaningful cosmic process seems to be on the agenda as a replacement for the meaningless mechanical cosmos that has dominated Western scientific thought and cultural life for a few hundred years.

Science Writer; Consultant; Lecturer, Copenhagen; Author, The Generous Man
Science Writer; Consultant; Lecturer, Copenhagen; Author, The User Illusion

I believe in belief—or rather: I have faith in having faith. Yet, I am an atheist (or a "bright" as some would have it). How can that be?

It is important to have faith, but not necessarily in God. Faith is important far outside the realm of religion: having faith in other people, in oneself, in the world, in the existence of truth, justice and beauty. There is a continuum of faith, from the basic everyday trust in others to the grand devotion to divine entities.

Recent discoveries in behavioural sciences, such as experimental economics and game theory, shows that it is a common human attitude towards the world to have faith. It is vital in human interactions; and it is no coincidence that the importance of anchoring behaviour in riskful trust is stressed in worlds as far apart as Søren Kierkegaard's existentialist christianity and modern theories of bargaining behaviour in economic interactions. Both stress the importance of the inner, subjective conviction as the basis for actions, the feeling of an inner glow.

One could say that modern behavioral science is re-discovering the importance of faith that has been known to religions for a long time. And I would argue that this re-discovery shows us that the activity of having faith can be decoupled from the belief in divine entities.

So here is what I have faith in: We have a hand backing us, not as a divine foresight or control, but in the very simple and concrete sense that we are all survivors. We are all the result of a very long line of survivors who survived long enough to have offspring. Amoeba, rodents and mammals. We can therefore have confidence that we are experts in survival. We have a wisdom inside, inherited from millions of generations of animals and humans, a knowledge of how to go about life. That does not in any way imply foresight or planning ahead on our behalf. It only implies that we have a reason to trust out ability to deal with whatever challenges we meet. We have inherited such an ability.

Therefore, we can trust each other, ourselves and life itself. We have no guarantee or promises for eternal life, not at all. The enigma of death is still there, ineradicable. 

But we a reason to have confidence in ourselves. The basic fact that we are still here—despite snakes, stupidity and nuclear weapons—gives us reason to have confidence in ourselves and each other, to trust others and to trust life. To have faith.

Because we are here, we have reason for having faith in having faith.

Former President, The Royal Society; Emeritus Professor of Cosmology & Astrophysics, University of Cambridge; Master, Trinity College; Author, From Here to Infinity
Cosmologist, Cambridge University; UK Astronomer Royal; Author, Our Final Hour

I believe that intelligent life may presently be unique to our Earth, but that, even so, it has the potential to spread through the galaxy and beyond—indeed, the emergence of complexity could still be near its beginning. If SETI searches fail, that would not render life a cosmic sideshow Indeed, it would be a boost to our cosmic self-esteem: terrestrial life, and its fate, would become a matter of cosmic significance. Even if intelligence is now unique to Earth, there's enough time lying ahead for it to spread through the entire Galaxy, evolving into a teeming complexity far beyond what we can even conceive.

There's an unthinking tendency to imagine that humans will be around in 6 billion years, watching the Sun flare up and die. But the forms of life and intelligence that have by then emerged would surely be as different from us as we are from a bacterium. That conclusion would follow even if future evolution proceeded at the rate at which new species have emerged over the 3 or 4 billion years of the geological past. But post-human evolution (whether of organic species or of artefacts) will proceed far faster than the changes that led to emergence, because it will be intelligently directed rather than being—like pre-human evolution—the gradual outcome of Darwinian natural selection. Changes will drastically accelerate in the present century—through intentional genetic modifications, targeted drugs, perhaps even silicon implants in to the brain. Humanity may not persist as a single species for more than a few centuries—especially if communities have by then become established away from the earth.

But a few centuries is still just a millionth of the Sun's future lifetime—and the entire universe probably has a longer future still. The remote future is squarely in the realm of science fiction. Advanced intelligences billions of years hence might even create new universes. Perhaps they'll be able to choose what physical laws prevail in their creations. Perhaps these beings could achieve the computational capability to simulate a universe as complex as the one we perceive ourselves to be in.

My belief may remain unprovable for billions of years. It could be falsified sooner—for instance, we (or our immediate post-human descendents) may develop theories that reveal inherent limits to complexity. But it's a substitute for religious belief, and I hope it's true.

Archaeologist, Journalist; Author, Artifacts
Archaeologist; Journalist; Writer-in-Residence, University of Bradford; Author, Past Poetic

I have a belief that modern humans are greatly underutilizing their cognitive capabilities. Finding proof of this, however, would lie in embracing those very same sentient possibilities—visceral hunches—which were possibly part of the world of archaic humans. This enlarged realm of the senses acknowledges reason, but also heeds the grip of the gut, the body poetic.

Physicist, University of Vienna; Scientific Director, Institute of Quantum Optics and Quantum Information; President, Austrian Academy of Sciences; Author, Dance of the Photons: From Einstein to Quantum Teleportation
Physicist

What I believe but cannot prove is that quantum physics teaches us to abandon the distinction between information and reality.

The fundamental reason why I believe in this is that it is impossible to make an operational distinction between reality and information. In other words, whenever we make any statement about the world, about any object, about any feature of any object, we always make statements about the information we have. And, whenever we make scientific predictions we make statements about information we possibly attain in the future. So one might be tempted to believe that everything is just information. The danger there is solipsism and subjectivism. But we know, even as we cannot prove it, that there is reality out there. For me the strongest argument for a reality independent of us is the randomness of the individual quantum event, like the decay of a radioactive atom. There is no hidden reason why a given atom decays at the very instant it does so.

So if reality exists and if we will never be able to make an operational distinction between reality and information, the hypothesis suggests itself that reality and information are the same. We need a new concept which encompasses both. In a sense, reality and information are the two sides of the same coin.

I feel that this is the message of the quantum. It is the natural extension of the Copenhagen interpretation. Once you adopt the notion that reality and information are the same all quantum paradoxes and puzzles disappear, like the measurement problem or Schrödinger's cat. Yet the price to pay is high. If my hypothesis is true, many questions become meaningless. There is no sense then to ask, what is "really" going on out there. Schrödinger's cat is neither dead nor alive unless we obtain information about her state.

By the way, I also believe that some day all computers will be quantum computers. The reason I believe this is the ongoing miniaturization of electronic components. And, certainly, we will learn to overcome decoherence. We will learn how to observe quantum phenomena outside the shielded environment of laboratories. I hope I will still be alive when this happens.

Computational Neuroscientist; Francis Crick Professor, the Salk Institute; Coauthor, The Computational Brain
Computational Neuroscientist, Howard Hughes Medical Institute; Coauthor, The Computational Brain

How do we remember the past? There are many answers to this question, depending on whether you are an historian, artist or scientist. As a scientist I have wanted to know where in the brain memories are stored and how they are stored¦the genetic and neural mechanisms. Although neuroscientists have made tremendous progress in uncovering neural mechanisms for learning, I believe, but cannot prove, that we are all looking in the wrong place for long-term memory.

I have been puzzled by my ability to remember my childhood, despite the fact that most of the molecules in my body today are not the same ones I had as a child¦in particular, the molecules that make up my brain are constantly turning over, being replaced with newly minted molecules. Perhaps memories only seem to be stable. Rehearsal strengthens memories, and can even alter them. However, I have detailed memories of specific places where I lived 50 years ago that I doubt I ever rehearsed but can be easily verified, so the stability of long-term memories is a real problem.

Textbooks in neuroscience, including one that I coauthored, say that memories are stored at synapses between neurons in the brain, of which there are many. In neural network models of memory, information can be stored by selectively altering the strengths of the synapses, and "spike-time dependent plasticity" at synapses in the cerebral cortex has been found with these properties. This is a hot area of research, but all we need to know here is that patterns of neural activity can indeed modify a lot of molecular machinery inside a neuron.

If memories are stored as changes to molecules inside cells, which are constantly being replaced, how can a memory remain stable over 50 years? My hunch is that everyone is looking in the wrong place: that the substrate of really old memories is located not inside cells, but outside cells, in the extracellular space. The space between cells is not empty, but filled with a matrix of tough material that is difficult to dissolve and turns over very slowly if at all. The extracellular matrix connects cells and maintains the shape of the cell mass. This is why scars on your body haven't changed much after decades of sloughing off skin cells.

My intuition is based on a set of classic experiments on the neuromuscular junction between a motor neuron and a muscle cell, a giant synapse that activates the muscle. The specialized extracellular matrix at the neuromuscular junction, called the basal lamina, consists of proteoglycans, glycoproteins, including collagen, and adhesion molecules such as laminin and fibronectin. If the nerve that activates a muscle is crushed, the nerve fiber grows back to the junction and forms a specialized nerve terminal ending. This occurs even if the muscle cell is also killed. The memory of the contact is preserved by the basal lamina at the junction. Similar material exists at synapses in the brain, which could permanently maintain overall connectivity despite the coming and going of molecules inside neurons.

How could we prove that the extracellular matrix really is responsible for long-term memories? One way to disprove it would be to disrupt the extracellular matrix and see if the memories remain. This can be done with enzymes or by knocking out one or more key molecules with techniques from molecular genetics. If I am right, then all of your memories¦what makes you a unique individual¦are contained in the endoskeleton that connects cells to each other. The intracellular machinery holds memories temporarily and decides what to permanently store in the matrix, perhaps while you are sleeping. It might be possible someday to stain this memory endoskeleton and see what memories look like.

theoretical physicist; Professor, Department of Physics, University of California, Santa Barbara
Theoretical Physicist, University of California, Santa Barbara

I believe that black holes do not destroy information, as Hawking argued long ago, and the reason is that strong gravitational effects undermine the statement that degrees of freedom inside and outside the black hole are independent. 

On the first point, I am far from alone; many string theorists and others now believe that black holes don't destroy information, and thus don't violate quantum mechanics. Hawking himself recently announced that he believes this, and has conceded a famous bet, but has not yet published the work giving a sharp statement where his original logic went wrong.

The second point I believe, but cannot yet prove to the point of convincing many of my colleagues. While many believe that Hawking was wrong, there is a lot of dissent over where exactly his calculation fails, and none of the arguments previously presented have sharply identified this point of failure. If black holes emit information instead of destroying it, this probably comes from a breakdown of locality. Lowe, Polchinski, Susskind, Thorlacius, and Uglum have argued that the mechanism for locality violation involves formation of long strings. Horowitz and Maldacena have argued that the singularity at the center of a black hole must be a unique state, in effect squeezing information out in a ghostly way. And others have made other suggestions.

But I believe, and my former student Lippert and I have published arguments, that the breakdown of locality that invalidates Hawking's work involves strong gravitational physics that makes it inconsistent to think of separate and independent degrees of freedom inside and outside the black hole. The assumption that these degrees of freedom are separate is fundamental to Hawking's argument. Our argument for where it fails has a satisfying generality that mirrors the generality of Hawking's original work—neither depends on the specifics of what kind of matter exists in the theory.

We base our argument on a principle we call the locality bound. This is a criterion for when physical degrees of freedom can be independent (in technical language, described by vanishing of commutators of corresponding operators). Roughly, a degree of freedom corresponding to a particle at position x with momentum p and another at y with momentum q will be independent only if the separation x-y is large enough that they are outside of a black hole that would form from their mutual energy. I believe this is the beginning of a general criterion (which will ultimately more precisely formulated) for when locality breaks down in physics. This could be the beginning of a deeper understanding of holography. And, it should be relevant to black hole physics because of the large relative energies of the Hawking radiation and degrees of freedom falling into a black hole. But this is not fully proven. Yet.

Planetary Scientist; Cassini Imaging Team Leader; Director, CICLOPS, Space Science Institute, Boulder, Colorado
Planetary Scientist; Leader, Cassini Imaging Team; Director, CICLOPS, Space Science Institute, Boulder

This is a treacherous question to ask, and a trivial one to answer. Treacherous because the shoals between the written lines can be navigated by some to the conclusion that truth and religious belief develop by the same means and are therefore equivalent. To those unfamiliar with the process by which scientific hunches and hypotheses are advanced to the level of verifiable fact, and the exacting standards applied in that process, the impression may be left that the work of the scientist is no different than that of the prophet or the priest.

Of course, nothing could be further from reality.

The whole scientific method relies on the deliberate, high magnification scrutiny and criticism by other scientists of any mechanisms proposed by any individual to explain the natural world. No matter how fervently a scientist may "believe'"something to be true, and unlike religious dogma, his or her belief is not accepted as a true description or even approximation of reality until it passes every test conceivable, executable and reproducible. Nature is the final arbiter, and great minds are great only in so far as they can intuit the way nature works and are shown by subsequent examination and proof to be right.

With that preamble out of the way, I can say that for me personally, this is a trivial question to answer. Though no one has yet shown that life of any kind, other than Earthly life, exists in the cosmos, I firmly believe that it does. My justification for this belief is a commonly used one, with no strenuous exertion of the intellect or suspension of disbelief required.

Our reconstruction of early solar system history, and the chronology of events that led to the origin of the Earth and moon and the subsequent development of life on our planet, informs us that self-replicating organisms originated from inanimate materials in a very narrow window of time. The tail end of the accretion of the planets—a period known as "the heavy bombardment"—ended about 3.8 billion years ago, approximately 800 million years after the Earth formed. This is the time of formation and solidification of the big flooded impact basins we readily see on the surface of the Moon, and the time when the last large catastrophe-producing impacts also occurred on the Earth. In other words, the terrestrial surface environment didn't settle down and become conducive to the development of fragile living organisms until nearly a billion years had gone by.

However, the first appearance of life forms on the Earth, the oldest fossils we have discovered so far, occurred shortly after that: around 3.5 billion years ago or even earlier. The interval in between—only 300 millions years and less than the time represented by the rock layers in the walls of the Grand Canyon—is the proverbial blink of the cosmic eye. Despite the enormous complexity of even the simplest biological forms and processes, and the undoubtedly lengthy and complicated chain of chemical events that must have occurred to evolve animated molecular structures from inanimate atoms, it seems an inevitable conclusion that Earthly life developed very quickly and as soon as the coast was clear long enough to do so.

Evidence is gathering that the events that created the solar system and the Earth, driven predominantly by gravity, are common and pervasive in our galaxy and, by inductive reasoning, in galaxies throughout the cosmos. The cosmos is very, very big. Consider the overwhelming numbers of galaxies in the visible cosmos alone and all the Sun-like stars in those galaxies and the number of habitable planets likely to be orbiting those stars and the ease with which life developed on our own habitable planet, and it becomes increasingly unavoidable that life is itself a fundamental feature of our universe ... along with dark matter, supernovae, and black holes.

I believe we are not alone. But it doesn't matter what I think because I can't prove it. It is so beguiling a question, though, that humankind is presently and actively seeking the answer. The search for life and so-called "habitable zones" is becoming increasingly the focus of our planetary explorations, and it may in fact transpire one day that we discover life forms under the ice on some moon orbiting Jupiter or Saturn, or decode the intelligible signals of an advanced, unreachably distant, alien organism. That will be a singular day indeed. I only hope I'm still around when it happens.

Professor of Philosophy and Psychology, NYU
Philosopher and Psychologist, New York University

I believe that the "Hard Problem of Consciousness" will be solved by conceptual advances made in connection with cognitive neuroscience. Let me explain. No one has a clue (at the moment) how to answer the question of why the neural basis of the phenomenal feel of my experience of red is the neural basis of that phenomenal feel rather than a different one or none at all. There is an "explanatory gap" here which no one has a clue how to close.

This problem is conceptually and explanatorily prior to the issue of what the nature of the self is, as can be seen in part by noting that the problem would persist even for experiences that are not organized into selves. No doubt closing the explanatory gap will require ideas that we cannot now anticipate. The mind-body problem is so singular that no appeal to the closing of past explanatory gaps really justifies optimism, but I am optimistic nonetheless.

Professor of Geography, University of California Los Angeles; Author, The World Until Yesterday
Biologist; Geographer, UCLA; Author, Collapse

When did humans complete their expansion around the world? I'm convinced, but can't yet prove, that humans first reached the continents of North America, South America, and Australia only very recently, at or near the end of the last Ice Age. Specifically, I'm convinced that they reached North America around 14,000 years ago, South America around 13,500 years ago, and Australia and New Guinea around 46, 000 years ago; and that humans were then responsible for the extinctions of most of the big animals of those continents within a few centuries of those dates; and that scientists will accept this conclusion sooner and less reluctantly for Australia and New Guinea than for North and South America.

Background to my conjecture is that there are now hundreds of thousands of sites with undisputed evidence of human presence dating back to millions of years ago in Africa, Europe, and Asia, but none with even disputed evidence of human presence over 100,000 years ago in the Americas and Australia. In the Americas, undisputed evidence suddenly appears in all the lower 48 U.S. states around 14,000 years ago, at numerous South American sites soon thereafter, and at hundreds of Australian sites between 46,000 and 14,000 years ago. Evidence of most of the former big mammals of those continents—e.g., elephants and lions and giant ground sloths in the Americas, giant kangaroos and one-ton Komodo dragons in Australia—disappears within a few centuries of those dates. The transparent conclusion: people arrived then, quickly filled up those continents, and easily killed off their big animals that had never seen humans and that let humans walk up to them, as Galapagos and Antarctica animals still do today.

But some Australian archaeologists, and many American archaeologists, resist this obvious conclusion, for several reasons. Archaeologists try hard to find convincing earlier sites, because it would be a dramatic discovery. Every year, discoveries of many purportedly older sites are announced, then to be forgotten. As the supporting evidence dissolves or remains disputed, we're now in a steady state of new claims and vanishing old claims, like a hydra constantly sprouting new heads. There are still a few sites known for the Americas with evidence of human butchering of the extinct big animals, and none known for Australia and New Guinea—but one expects to find very few sites anyway, among all the sites of natural deaths for hundreds of thousands of years, if the hunting was all finished locally (because the prey became extinct) within a few decades. American archaeologists are especially persistent in their quest for pre-14,000 sites—perhaps because secured dating requires use of multiple dating techniques (not just radiocarbon), but American archaeologists distrust alternatives to radiocarbon (discovered by U.S. scientists) because the alternative dating techniques were discovered by Australian scientists.

Every year, beginning graduate students in archaeology and paleontology, working in Africa or Europe or Asia, go out and discover undisputed new sites with ancient human presence. Every year, new such discoveries are announced to the other three continents, but none has ever met the requirements of evidence accepted for Africa, Europe, or Asia. The big animals of the latter three continents survive, because they had millions of years to learn fear of human hunters with very slowly evolving skills; most big animals of the former three continents didn't survive, because they had the misfortune that their first encounter with humans was a sudden one, with fully modern skilled hunters.

To me, the case is already proved. How many more decades of unconvincing claims will it take to convince the holdouts among my colleagues? I don't know. It makes better newspaper headlines to report "Wow!! New discovery overturns the established paradigm of American archaeology!!" than to report, "Ho hum, yet another reportedly paradigm-overturning discovery fails to hold up."

Professor of Physics and Director of the Institute of Cosmology at Tufts University
Physicist; Institute of Cosmology, Tufts University

There are good reasons to believe that the universe is infinite. 

If so, it contains an infinite number of regions of the same size as our observable region (which is 80 billion light years across). It follows from quantum mechanics that the number of distinct histories that could occur in any of these finite regions in a finite time (since the big bang) is finite. By history I mean not just the history of the civilization, but everything that happens, down to the atomic level. The number of possible histories is fantastically large (it has been estimated as 10 to the power 10 to the power 150), but the important point is that it is finite.

Thus, we have an infinite number of regions like ours and only a finite number of histories that can play out in them. It follows that every possible history will occur in an infinite number of regions. In particular, there should be an infinite number of regions with histories identical to ours. So, if you are not satisfied with the result of the presidential elections, don't despair: you candidate has won on an infinite number of earths.

This picture of the universe robs our civilization of any claim for uniqueness: countless identical civilizations are scattered in the infinite expanse of the cosmos. I find this rather depressing, but it is probably true.

Another thing that I believe to be true, but cannot prove, is that our part of the universe will eventually stop expanding and will recollapse to a big crunch. But this will happen no sooner than 20 billion years from now, and probably much later.

Communications Expert; Author, Smart Mobs
Communications Expert; Author, Smart Mobs

I believe that we humans, who know so much about cosmology and immunology, lack a framework for thinking about why and how humans cooperate. I believe that part of the reason for this is an old story we tell ourselves about the world:  Businesses and nations succeed by competing well. Biology is a war, where only the fit survive. Politics is about winning. Markets grow solely from self-interest. Rooted in the zeitgeist of Adam Smith's and Charles Darwin's eras, the scientific, social, economic, political stories of the 19th and 20th centuries overwhelmingly emphasized the role of competition as a driver of evolution, progress, commerce, society.

I believe that the outlines of a new narrative are becoming visible—a story in which cooperative arrangements, interdependencies, and collective action play a more prominent role and the essential (but not all-powerful) story of competition and survival of the fittest shrinks just a bit.

Although new knowledge in biology about the evolution of altruistic behavior and the role of symbiotic relationships, new understandings of economic behavior derived from experiments in game theory, neuroeconomic research, sociological investigations of institutions for collective action, computation-enabled technologies such as grid computing, mesh networks, and online markets all provide important clues, I don't believe anyone is likely to formulate an algorithm or recipe for human cooperation. I suspect that the complex interdependencies of human thought, behavior and culture entails an equivalent to the limits Heisenberg found to physics and Gödel established for mathematics.

I believe that more knowledge than what we have now, together with a conceptual framework that is neither reductionistic nor theological, could lead to better-designed economic and political policies and institutions. Institutional and conceptual barriers to mounting such an effort are as formidable as the methodological barriers. I am reminded of Doug Engelbart's problem in the 1950s. He couldn't convince computer engineers, librarians, public policy analysts that computing machinery could be used to augment human thinking, as well as performing scientific calculation and business data processing. Nobody and no institution had ever thought about computing machinery that way, and older ways of thinking about what machines could be designed to do were inadequate. Engelbart had to create "A Framework for Augmenting Human Intellect" before the various hardware, software, and human interface designers could create the first personal computers and networks.

By necessity, useful new understandings of how humans cooperate and fail to cooperate is an interdisciplinary task. I don't believe that the obvious importance of such an effort guarantees that it will be successfully accomplished. All our institutions for gathering and validating knowledge—universities, corporate research laboratories, and foundations—reward and support specialization.

Software Engineer, Computer Scientist, Entrepreneur, Philanthropist
Computer Scientist; Founder, Intentional Software; formerly Chief Architect, Microsoft

I believe that we are writing software the wrong way. There are sound evolutionary reasons for why we are doing what we are doing—that we can call the "programming the problem in a computer language" paradigm, but the incredible success of Moore's law blinded us to being stuck in what is probably an evolutionary backwater.

There are many warning signs. Computers are demonstrably ten thousand times better than not so long ago. Yet we are not seeing their services improving at the same rate (with some exceptions—for example games and internet searches.) On an absolute scale, a business or administration problem that would take maybe one hundred pages to describe precisely, will take millions of dollars to program for a computer and often the program will not work. Recently a smaller airline came to a standstill due to a problem in crew scheduling software—raising the ire of Congress, not to mention their customers.

My laptop could store 200 pages of text (1/2 megabytes) for each and every crew member at this airline just in its fast memory and hundred times more (a veritable encyclopedia of 20,000 pages) for each person on its hard disk. Of course for a schedule we would need maybe one or two—or at most ten pages per person. Even with all the rules—the laws, the union contracts, the local, state, federal taxes, the duty time limitations, the FAA regulations on crew certification; is there anyone who believes that the problem is not simple in terms of computing? We need to store and process at the maximum 10 pages per person where we have capacity for two thousand times more in one cheap laptop! Of course the problem is complex in terms of the problem domain—but not shockingly so. I would estimate that all the rules possibly relevant to aircraft crew scheduling are expressible in less than a thousand pages—or 1/2 of one percent of the fast memory.

Software is surely the bottleneck on the high-tech horn of plenty. The scheduling program for the airline takes many thousand times more memory than what I believe it should be. Hence the software represents complexity that is many thousand times greater than what I believe the problem is—no wonder that some planes are assigned three pilots by the software while the others can't fly because the copilot is not scheduled. Note that the cost of the memory is not the issue—we could afford that waste. But the use of so much memory for software is an indication of some complexity inflation that occurs during programming that is the real bottleneck.

What is going on? I like to use cryptography as the metaphor. As we know, in cryptography we take a message and we combine it with a key using a difficult-to-invert function to get the code. Programmers using today's paradigm start from a problem statement, for example that a Boeing 767 requires a pilot, a copilot, and seven cabin crew with various certification requirements for each—and combine this with their knowledge of computer science and software engineering—that is how this rule can be encoded in computer language and turned into an algorithm. This act of combining is the programming process, the result of which is called the source code. Now, programming is well known to be a difficult-to-invert function, perhaps not to cryptography's standards, but one can joke about the possibility of the airline being able to keep their proprietary scheduling rules secret by publishing the source code for the implementation since no one could figure out what the rules were—or really whether the code had to do with scheduling or spare parts inventory—by studying the source code, it can be that obscure.

The amazing thing is that today it is the source code—that is the encrypted problem—which is the artifact all of software engineering is focusing on. To add insult to the injury, the "encryption", that is programming, is done manually which means high costs, low throughput and high error rates. In contrast with software maintenance, when the General realizes that he is about to send a wrong encrypted message, no one would think of editing the code after the encryption or "fixing the code"; instead the clear text would be first edited and then this improved message would be re-encrypted at computer speeds and computer accuracy. In other words the message may be wrong, but it won't be wrong because of the encryption and it is easily fixed.

We see that the complexity inflation comes from encoding. The problem statement above is obviously oversimplified, but remember that we used just two lines from our realistic budget of a thousand pages and we haven't even used the aviation jargon which can make these statements even more compact and more precise. But once these statements are viewed through the funhouse mirror of software coding, it becomes all but unrecognizable: thousand times fatter, disjointed, foreign. And as any manual product, it will have many flaws—beyond the errors in the rules themselves.

What can be done? Follow the metaphor. First, refocus on recording the problem statement—the "cleartext" in our metaphor. This is not a program in any sense of the word—it is just a straightforward recording of the subject matter experts' contributions using their own terms-of-art, their jargon, their own notations. Next, empower the programmers to program not the problem itself, but to express their software engineering expertise and decisions as a computer code for the encoder that takes the recorded problem statement and generates the code from it. This is called generative programming and I believe it is the future of software.

Psychologist; Author, Ecological Intelligence, Focus: The Hidden Driver of Excellence
Psychologist; Author, Emotional Intelligence

I believe, but cannot prove, that today's children are unintended victims of economic and technological progress.

To be sure, greater wealth and advanced technology offers all of us better lives in many ways. Yet these unstoppable forces seem to have had some disastrous results in how they have been transforming childhood. Even as children's IQs are on a steady march upward over the last century, the last three decades have seen a major drop in children's most basic social and emotional skills—the very abilities that would make them effective workers and leaders, parents and spouses, and members of the community.

Of course there are always individual exceptions—children who grow up to be outstanding human beings. But the Bell Curve for social and emotional abilities seems to be sliding in the wrong direction. The most compelling data comes from a random national sample of more than 3,000 American children ages seven to sixteen—chosen to represent the entire nation—rated by their parents and teachers, adults who know them well. First done in the early 1970s, and then roughly fifteen years later, in the mid-80s, and again in the late 1990s, the results showed a startling decline.

The most precipitous drop occurred between the first and second cohorts: American children were more withdrawn, sulky and unhappy, anxious and depressed, impulsive and unable to concentrate, delinquent and aggressive. Between the early 1970s and the mid-80s, they did more poorly on 42 indicators, better on none. In the late 1990s, scores crept back up a bit, but were nowhere near as high as they had been on the first round, in the early 70s.

That's the data. What I believe, but can't prove, is that this decline is due in large part to economic and technological forces. For one, the ratcheting upward of global competition means that over the last two decades or so each generation of parents has had to work longer to maintain the same standard of living that their own parents had—virtually every family has two working parents today, while 50 years ago the norm was only one. It's not that today's parents love their children any less, but that they have less free time to spend with them than was true in their parents' day.

Increasing mobility means that fewer children live in the same neighborhood as their extended families—and so no longer have surrogate parenting from close relatives. Day care can be excellent, particularly for children of privileged families, but too often means less well-to-do children get too little caring attention in their day.

For the middle class, childhood has become overly organized, a tight schedule of dance or piano lessons and soccer games, children shuttled from one adult-run activity to another. This has eroded the free time in which children can play together on their own, in their own way.

When it comes to learning social and emotional skills, I suspect the lessoning of open time with family, relatives and other children translates into a loss of the very activities that have traditionally allowed the natural transmission of these skills.

Then there's the technological factor. Today's children spend more time than ever in human history alone, staring at a video monitor. That amounts to a natural experiment in childrearing on an unprecedented scale. While this may mean children as adults will be more at ease with their computers, I doubt it does anything but de-skill them when it comes to relating to each other person-to-person.

We know that the prefrontal-limbic neural circuitry crucial for social and emotional abilities is the last part of the human brain to become anatomically mature, not finishing this developmental task until the mid-20s. During that window, children's life abilities become set as neurons come online and are interconnected for better or for worse. A child's experiences dictate how those connections are made.

A smart strategy for helping every child get the right social and emotional skill-building would be to bring such lessons into the classroom rather than leaving it to chance. My hunch, which I can't prove, is that this offers the best way to keep children from paying of modern life for us all.

Chief News and Features Editor
Writer; Contributing Editor, Wired, Newsweek International; Author, Mapping Mars.

I've always found belief a bit difficult; people tend to assume that I have rather strong beliefs, but I don't experience them in that way. As far as knowledge goes I'm a consumer, and sometimes a distributor, not a producer; most of what I believe to be true lies far beyond my capacity for proof, and I try to moderate the timbre of my belief accordingly. I know that almost all my beliefs are based on faith in people, and processes, and institutions, and their various capacities for correcting themselves when in error.

I think the same is true for most of us; those who can prove their beliefs in their field of expertise are still reliant on faith in others when it comes to other fields. To acknowledge this at all times is not possible—it would make every utterance tentative, encrust every concept with ceteris paribus clauses. But when faced with a question like this, the role of our faith in people and in social institutions has to be acknowledged. And it does no harm to acknowledge it now and then even when not faced with such a question, in order to reinforce the need to keep people, institutions and the processes of knowledge production held in helpful scrutiny.

Which I suppose means that, for me, the real question is what do I believe that I don't think anyone can prove. In answer I'd put forward the belief that there is a future much better, in terms of reduced human suffering and increased human potential, than the present, and that one part of what makes it better is a greater, subtler knowledge of the world at large.

If I can't prove this, why do I believe it? Because it's better than believing the alternative. Because it provides a context for social and political action that would otherwise be futile; in this, it is an exhortatory belief. It is also, in part, a self-serving one, in that it suggests that by trying to clarify and disseminate knowledge (a description that makes me sound like the chef at a soup kitchen) I'm doing something that helps the better future, if only a bit.

Besides the question of why, though, there's the question of how. And there the answer is "with difficulty". It is not an easy thing for me to make myself believe. But it is what I want to believe, and on my best days I do.

Vice President of Research, George Washington University
Ophthalmologist and Neurobiologist, University of California, Davis

Here are three of my unproven beliefs:

(i) The human brain is the most complex entity in the known universe;

(ii) With this marvelous product of evolution we will be successful in eventually discovering all that there is to discover about the physical world, provided of course, that some catastrophic event doesn't terminate our species; and

(iii) Science provides the best means to attain this ultimate goal.

When the scientific endeavor is considered in relation to the obvious limitations of the human brain, the knowledge we have gained in all fields to date is astonishing. Consider the well-documented variability in the functional properties of neurons. When recordings are made from a single cell—for instance in the visual cortex to a flashing spot of light—one can't help but be amazed by the trial-to-trial variations in the resulting responses.

On one trial this simple stimulus might elicit a high frequency burst of discharges, while on the next trial there could be just a hint of a response. The same thing is apparent when EEG recordings are made from the human brain. Brain waves change in frequency and amplitude in seemingly random fashion even when the subject is lying in a prone position without any variations in behavior or the environment. 
And such variability is also evident when one does brain imaging; the pretty pictures seen in publications are averages of many trials that have been "massaged" by various computer programs.

So how does the brain do it? How can it function as effectively as it does given the "noise" inherent in the system? I don't have a good answer, and neither does anyone else, in spite of the papers that have been published on this problem. But in line with the second of the three beliefs I have listed above, I am certain that someday this question will be answered in a definitive manner.

Curator, TED conferences, TED Talks
Editor-In-Chief, Wired

The Intelligent Design movement has opened my eyes. I realize that although I believe that evolution explains why the living world is the way it is, I can't actually prove it. At least not to the satisfaction of the ID folk, who seem to require that every example of extraordinary complexity and clever plumbing in nature be fully traced back (not just traceable back) along an evolutionary tree to prove that it wasn't directed by an invisible hand. If the scientific community won't do that, then the arguments goes that they must accept a large red "theory" stamp placed on the evolution textbooks and that alternative theories, such as "guided" evolution and creationism, be taught alongside.

So, by this standard, virtually everything I believe in must now fall under the shadow of unproveability. Most importantly, this includes the belief that democracy, capitalism and other market-driven systems (including evolution!) are better than their alternatives. Indeed, I suppose I should now refer to them as the "theory of democracy" and the "theory of capitalism", to join the theory of evolution, and accept the teaching of living Marxism and fascism as alternatives in high schools.

Computer Scientist, UC Berkeley, School of Information; Author, Search User Interfaces
Computer Scientist, UC Berkeley, School of Information Management & Systems

The Search Problem is solvable.

Advances in computational linguistics and user interface design will eventually enable people to find answers to any question they have, so long as the answer is encoded in textual form and stored in a publicly accessible location. Advances in reasoning systems will to a limited degree be able to draw inferences in order to find answers that are not explicitly present in the existing documents.

There have been several recent developments that prompt me to make this claim. First, computational linguistics (also known as natural language processing or language engineering) has made great leaps forward in the last decade, due primarily to advances stemming from the availability of huge text collections, from which statistics can be derived. Today's automatic language translation systems, for example, are now derived almost entirely from statistical patterns extracted from text collections. They now work as well as hand-engineered systems, and promise to continue to improve. As another example, recent government-sponsored research in the area of (simple) question answering has produced a radical leap forward in the quality of results in this arena.

Of course, another important development is the rise of the Web and its most voracious consumer, the internet search engine. It is common knowledge that search engines make use of information associated with link structure to improve results rankings. But search engine companies also have enormous, albeit somewhat impoverished, repositories of information about how people ask for information. This behavioral information can be used to build better search tools. For example, some spelling correction algorithms make use of how people have corrected erroneous spellings in the past, by observing pairs of queries that occur one after the next. The second query is assumed to be the correction, if it is sufficiently similar to the first. Patterns are then derived that convert from different types of misspellings to their corrections.

Another development in the field of computational linguistics is the manual creation of enormous lexical ontologies, which are then used to build axioms and rules about language use. These modern ontologies, unlike their predecessors, are of a large enough scale and simple enough design to be useful, although this work is in the early stages. There are also many attempts to build such ontologies automatically from large text collections; the most promising approach seems to be to combine the automated and the manual approaches.

As a side note, I am skeptical about the hype surrounding the Semantic Web—it is very difficult to characterize concepts in a systematic way, and even more so to force all the world's creators of information to conform to one schema. Automated analysis tools adapt to what people really do, rather than try to force people's expressions of information to conform to a standard.

Finally, advances in user interface design are key to producing better search results. The search field has learned an enormous amount in the ten years since the Web became a major presence in society, but as is often noted in the field, the interface itself hasn't changed much: after all this time, we still type words into a blank box and then select from a list of results. Experience shows that a search interface has to be a qualitative leap better than the standard in order to entice people to switch. I believe headway will be made in this area, most likely occurring in tandem with advances in natural language analysis.

It may well be the case that advances in audio, image, and video processing will keep pace with those of language analysis, thus making possible the answering of questions that can be answered by information stored in graphical and audio form. However, my expertise does not extend to these fields, so I will not make a claim about this.

Albert Einstein Professor in Science, Departments of Physics and Astrophysical Sciences, Princeton University; coauthor: Endless Universe
Albert Einstein Professor of Physics, Princeton University.

I believe that our universe is not accidental, but I cannot prove it. 

Historically, most physicists have shared this point-of-view. For centuries, most of us have believed that the universe is governed by a simple set of physical laws that are the same everywhere and that these laws derive from a simple unified theory. 

However, in the last few years, an increasing number of my most respected colleagues have become enamored with the anthropic principle—the idea that there is an enormous multiplicity of universes with widely different physical properties and the properties of our particular observable universe arise from pure accident. The only special feature of our universe is that its properties are compatible with the evolution of intelligent life. The change in attitude is motivated, in part, by the failure to date to find a unified theory that predicts our universe as the unique possibility. According to some recent calculations, the current best hope for a unified theory—superstring theory—allows an exponentially large number of different universes, most of which look nothing like our own. String theorists have turned to the anthropic principle for salvation. 

Frankly, I view this as an act of desperation. I don't have much patience for the anthropic principle. I think the concept is, at heart, non-scientific. A proper scientific theory is based on testable assumptions and is judged by its predictive power. The anthropic principle makes an enormous number of assumptions—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.—none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation. As for predictions, there are very few, if any. In the case of string theory, the principle is invoked only to explain known observations, not to predict new ones. (In other versions of the anthropic principle where predictions are made, the predictions have proven to be wrong. Some physicists cite the recent evidence for a cosmological constant as having anticipated by anthropic argument; however, the observed value does not agree with the anthropically predicted value.)

I find the desperation especially unwarranted since I see no evidence that our universe arose by a random process. Quite the contrary, recent observations and experiments suggest that our universe is extremely simple. The distribution of matter and energy is remarkably uniform. The hierarchy of complex structures ranging from galaxy clusters to subnuclear particles can all be described in terms of a few dozen elementary constituents and less than a handful of forces, all related by simple symmetries. A simple universe demands a simple explanation. Why do we need to postulate an infinite number of universes with all sorts of different properties just to explain our one? 

Of course, my colleagues and I are anxious for further reductionism. But I view the current failure of string theory to find a unique universe simply as a sign that our understanding of string theory is still immature (or perhaps that string theory is wrong). Decades from now, I hope that physicists will be pursuing once again their dreams of a truly scientific "final theory" and will look back at the current anthropic craze as millennial madness.

Theoretical Physicist; Aix-Marseille University, in the Centre de Physique Théorique, Marseille, France; Author, The First Scientist: Anaximander and His Legacy
Physicist; Institut Universitaire de France & University of the Mediterraneum; Author, Quantum Gravity

I am convinced, but cannot prove, that time does not exist. I mean that I am convinced that there is a consistent way of thinking about nature, that makes no use of the notions of space and time at the fundamental level. And that this way of thinking will turn out to be the useful and convincing one.

I think that the notions of space and time will turn out to be useful only within some approximation. They are similar to a notion like "the surface of the water" which looses meaning when we describe the dynamics of the individual atoms forming water and air: if we look at very small scale, there isn't really any actual surface down there. I am convinced space and time are like the surface of the water: convenient macroscopic approximations, flimsy but illusory and insufficient screens that our mind uses to organize reality.

In particular, I am convinced that time is an artifact of the approximation in which we disregard the large majority of the degrees of freedom of reality. Thus "time" is just the reflection of our ignorance.

I am also convinced, but cannot prove, that there are no objects, but only relations. By this I mean that I am convinced that there is a consistent way of thinking about nature, that refers only to interactions between systems and not to states or changes of individual systems. I am convinced that this way of thinking nature will end up to be the useful and natural one in physics.

Beliefs that one cannot prove are often wrong, as proven by the fact that this Edge list contains contradictory beliefs. But they are essential in science and often healthy. Here is a good example from 25 centuries ago: Socrates, in Plato's Phaedon says:

"... seems to me very hard to prove, and I think I wouldn't be able to prove it ... but I am convinced ... that the Earth is spherical."

Finally, I am also convinced, but cannot prove, that we humans have an instinct to collaborate, and that we have rational reasons for collaborating. I am convinced that ultimately this rationality and this instinct of collaboration will prevail over the shortsighted egoistic and aggressive instinct that produces exploitation and war. Rationality and instinct of collaboration have already given us large regions and long periods of peace and prosperity. Ultimately, they will lead us to a planet without countries, without wars, without patriotism, without religions, without poverty, where we will be able to share the world. Actually, maybe I am not sure I truly believe that I believe this; but I do want to believe that I believe this.

emeritus professor of the Philosophy department of the University of Calgary, Alberta Canada
Mathematician, Emeritus Professor, Dept of Philosophy, University of Calgary; Author, Gödel's Theorems

Most of what I believe I cannot prove, simply for lack of time and energy; truths that I'd claim to know because they have been proved by others. That is how inextricably our beliefs are tied up with labors accomplished by fellow beings. And then there are mathematical truths that we now know are not provable. These phenomena have become favorites with the media but can only be made sense of by a serious scrutiny of the idea of mathematical truth and a specific articulation of a proof-concept,

But running across Esther's contribution I came up with a catchy response:

I believe in the creative power of boredom.

Or, to put it into the form suggested by the Edge question:

I believe that, no matter how relentlessly we overfeed our young with prepackaged interactive entertainments, before long they will break out and invent their own amusements. I know from experience; boredom drove me into mathematics during my preteens. But I cannot prove it, till it actually happens. Probably in less than a generation kids will be amusing themselves and each other in ways that we never dreamt of.

Such is my belief in human nature, in the resilience of its good sense.

Here is an observation from mathematical practice. By now the concept of an algorithm, well- defined, is widely hailed as the way to solve problems, more precisely sequences of problems labeled by a numerical parameter. The implementation of a specific algorithm may be boring, a task best left to a machine, while the construction of the algorithm together with a rigorous proof that it works is a creative and often laborious enterprise.

For illustration consider group theory. A group is defined as a structure consisting of a non-empty set and a binary operation obeying certain laws. The theory of groups consists of all sentences true of all groups; its restriction to the formal "first order" language L determined by the group structure is called the elementary theory TG of groups. Here we have a formal proof procedure, proven complete by Gödel in his PHD thesis the year before his incompleteness proof was published. The elementary theory of groups is axiomatizable: it consists of exactly those sentences that are derivable from the axioms by means of the rules of first order logic. Thus TG is an effectively (recursively) enumerable subset of L; a machine, unlimited in power and time, could eventually come up with a proof of every elementary theorem of group theory. However, a human group theorist would still be needed to select the interesting theorems out of the bulk of the merely true. The development of TG is no mean task, although its language is severely restricted.

The axiomatizability of a theory always raises the question how to recognize the non-theorems. The set FF of those L-sentences that fail in some finite group is recursively enumerable by an enumeration of all finite groups, a simple matter, in principle. But, as all the excitement over the construction of finite simple monsters has amply demonstrated, that again is in reality no simple task.

Neither the theory of finite groups nor the theory of all groups is decidable. The most satisfying proof of this fact shows how to construct to every pair (A, B) of disjoint recursively enumerable sets of L-sentences, where A contains all of TG and B contains FF, a sentence S that belongs neither to A nor to B. This is the deep and sophisticated theorem of effective non-separability proved in the early sixties independently by Mal'cev in the SSSR and Tarski's pupil Cobham.

It follows that constructing infinite counter-examples in group theory is a truly creative enterprise, while the theory of finite groups is not axiomatizable and so, to recognize a truth about finite groups requires deep insight and a creative jump. The concept of finiteness in group theory is not elementary and yet we have a clear idea of what is meant by talking about all finite groups, a marvelously intriguing situation.

To wind up with a specific answer to the 2005 Question:

I do believe that every sentence expressible in the formal language of elementary group theory is either true of all finite groups or else fails for at least one of them.

This statement may at first sight look like a logical triviality. But when you try to prove it honestly you find that you would need a decision procedure, which would, given any sentence of L, yield either a proof that S holds in all finite groups or else a finite group in which S fails. By the inseparability theorem mentioned above, there is no such procedure.

If asked whether I hold the equivalent belief for the theory of all groups I would hesitate because the concept of an infinite counterexample is not as concrete to my mind as that of the totality of all finite groups. These are the areas where personal intuition starts to come into play.