1999 : WHAT IS THE MOST IMPORTANT INVENTION IN THE PAST TWO THOUSAND YEARS?

DNI: DISTRIBUTED NETWORKED INTELLIGENCE

In their classic book The Mathematical Theory of Communication, Claude Shannon and Warren Weaver stated: "The word communication will be used here in a very broad sense to include all of the procedures by which one mind may affect another. This, of course, involves not only written and oral speech, but also music, the pictorial arts, the theater, the ballet, and in fact all human behavior."

Marshall McLuhan pointed out that by inventing electric technology, we had externalized our central nervous systems; that is, our minds. We had gone beyond Freud's invention of the unconscious, and, for the first time, had rendered visible the conscious.

Composer John Cage went further to say that we now had to presume that "there's only one mind, the one we all share." Cage pointed out that we had to go beyond private and personal mind-sets and understand how radically things had changed. Mind had become socialized. "We can't change our minds without changing the world," he said. Mind as an extension became our environment, which he characterized as "the collective consciousness," which we could tap into by creating "a global utilities network."

We create tools and then mold ourselves in their image. Seventeenth-century clockworks inspired mechanistic metaphors ("the heart is a pump") just as mid-twentieth-century developments in self-regulating engineering devices resulted in the cybernetic image ("the brain is computer").

Although you don't hear much about cybernetics today in the scientific arena, its impact is profound. "The cybernetic idea" stated anthropologist Gregory Bateson, "is the most important abstraction since the invention of Jesus Christ." He went on to note that we were now living in " a world of pattern, of order, of resonances in which the individual mind is a subsystem of a larger order. Mind is intrinsic to the messages carried by the pathways within the larger system and intrinsic also in the pathways themselves."

In this new epistemology Ockham's Razor meets Gödel's Proof and the fabric of our habitual thinking is torn apart. Subject and object fuse. The individual self decreates. (See By The Late John Brockman). Reality passes into description and thus becomes invention. Such ideas, which appear destructive, liberate, allowing us to lay waste to the generalizations of previous epochs which we decreate by getting through the history of our words. As Wallace Stevens wrote: "The words of the world are the life of the world. It is the speech of truth in its true solitude: a nature that is created in what it says."*

Key to this radical rebooting of our mindsets is the terminformation, which, in this scheme, refers to regulation and control and has nothing to do with meaning, ideas, or data. Bateson pointed out that "information is a difference that makes a difference." The raindrop that hits the ground behind you contains no information. The raindrop that hits you on the nose has information. Information is a measure of effect. Systems of control utilize information if and when they react to change to maintain continuity.

If Newtonian physics taught us that it is the parts that matter, we now inhabit a universe that interacts infinitely with itself, where importance lies in the patterns that connect the parts. This becomes problematic because how can a system describe itself without generating a spiralling ladder of recursive mirrors?

The answer?

Nobody knows, and you can't find out.

The description of the plane of language is the plane that holds our descriptions. Language becomes a commission, a dance, a play, a song.

With the Internet we are creating a new extension of ourselves in much the same way as Mary Shelley's Dr. Frankenstein pieced together his creation. Only this creation is not an anthropomorphic being that moves through accretive portions of space in time. It is instead, an emergent electronic beast of such proportions that we can only imagine its qualities, its dimensions.

Can it be ourselves?

I propose as the most important invention of the past two thousand years: Distributed Networked Intelligence (DNI). DNI is the collective externalized mind, the mind we all share, the infinite oscillation of our collective consciousness interacting with itself, adding a fuller, richer dimension to what it means to be human.

To avoid incurring the wrath of some scholars, I wanted to add this parenthetical note (see asterisk below) to my statement about language. Hopefully, it clarifies my point a little; or, at least, focuses it.

My first candidate is "language"; specifically, our initial realization* of its creative potential, building on the intuitions of the ancient Greeks and Romans. Language is the life-force and body of communica- tion. It comprises all forms of symbolic creations, expressions and systems which we use to communicate: from the mathematical to the vernacular. Without language, every other invention and innovation may never have existed -- including humor!

My close-second candidate is E = mc2. When we learn to tap the full meaning of that piece of symbolic language, we'll create more than a Nuclear Age. "Matter is frozen energy," Einstein said, relating the essence of his insight into the mass-energy relationship. Similarly, language is frozen meaning. When we discover how to unleash the enormous energy in meaning by continually transforming information (data, ideas, knowledge, experience) in new contexts, we'll make a quantum leap in applying the power of language to achieve our boldest dreams.

* Note: Some people may choose to date our first deep realization of language's potential around the late 1700's. That's when the first scientific study of the nature and origins of language began to unfold through the systematic, comparative studies of the German scholars Friedrich Schlegel, Jakob Grimm, and Franz Bopp. Others may focus on the work of Ferdinand de Saussure whose general, descriptive method led to some basic laws that relate to all languages (about 3,000 or more now). My broad statement is meant to embrace the "makeup" of language: its symbolic nature, structures, semantics, and boundless usages. I'm not simply referring to the inventive act of classifying spoken and written languages into families, or categorizing the growth patterns of language, or charting the evolution of grammar.

Most of the inventions mentioned thus far have affected, as one contributor put it, the boundary between we humans and the natural world that surrounds us. But the operations of the human body, and the brain which it contains, support all of the experiences that make up our existence. Discoveries that will permit us ultimately to take charge of these functions, and shape them to our desires, surely deserve nomination as the most important of the last two millennia. These insights have flowed broadly from the entire area of science that is now called molecular biology, but if I had to single out the most important invention that made the entire process possible, then I would select genetic sequencing for the honor. The new techniques developed by Fred Sanger in Cambridge and Walter Gilbert at Harvard in the mid-1970's allowed us to read out rapidly the specific information stored in our genes and those of all other living creatures on Earth.

The new methods stimulated a burst of scientific energy that will culminate in the next decade, when the sequence of about 3 billion characters of DNA that encodes a typical human being will be fully deciphered by the Human Genome Project. In subsequent explorations, we shall how individuals differ in their heredity, and how this information is expressed to produce the human body.

Thus far the effects of sequencing have largely impacted us through such media worthy events as the identification of the stain on Monica Lewinsky's dress, validation of the identity of the Romanov bones, refutation of the claim of Anna Anderson to be Anastasia and confirmation of Thomas Jefferson's affair with Sally Hemings. Much, much more is yet to come.

The completion of the Human Genome Project will provide us with an understanding, at the molecular level, of human hereditary disease (much has already been learned about Huntington's disease, cystic fibrosis and others). Further, by the application of other tools from modern molecular biology, we shall be able to do something about these afflictions in the near future.They will be treated and, if society permits it, corrected at the genetic level. Beyond that, we shall come to understand, and perhaps control, many unfortunate aspects of the human condition that have until now been taken for granted, from baldness to aging. Ultimately, we may elect to rewrite our genetic text, changing ourselves and the way in which we experience the universe.

Much more has been written on these subjects, but I hope that the above brief treatment should be enough to qualify genetic sequencing for the short list of finalists in this contest. I will also suggest that any poll taken now would not do justice to this invention, as most of its consequences still lie ahead of us. Perhaps we should schedule another poll for the year 3998, to determine the best invention in the period AD 1-2000?

Let's ignore discoveries (germs) and technique (scientific method) for starters before determining the greatest invention. I also think that the printing press, a device invented to rip-off the bible buying public, should be relegated to its rightful place as number two to a newer invention: computer networks. While it is quaint to romanticize the past by citing the printing press, steam engines or 18th century lug nuts, we ignore the fact that our inventiveness as a civilization is increasing not decreasing and newer inventions might be the most important inventions. And let's choose an invention in and of itself and not argue about derivatives. Right now the invention that is revolutionizing the world (more than TV, for sure) is the computer network — the Internet in particular. And, for what it's worth, arguing that none of this would be possible if man hadn't learned to grunt first, therefore grunting in the most important invention is nonsense.

More interesting in this artificial discussion is how most of the participants, including myself, have chosen an invention from their particular specialty. Perhaps we should ask the question: what is the most insidious invention of the past 2000 years? How about specialization? Look at how insidious it is in this discussion. So much so that it's frightening. Change the topic! Discussing the most insidious inventions would be more fun than talking about the importance of hay, the concept of infinity or Goedel! Just think of the possibilities. We can nominate plastic, the stock market, roller pens, the vibrating dildo, sitcoms, the literary agent, Microsoft Visual BASIC, the animated cartoon, CNN, the wrist watch, roller blades, the spinach souffle. The possibilities are endless. Let's start over.

Well, this isn't very imaginative, but my choice-like that of several other contributors-is the pill. Here's my reasoning. The greatest invention of the last 2000 years is the one that is most likely to help avert the collapse of civilization in the next 2000. Electricity as a means of information and energy transport is a candidate. Modern medicine is a candidate. But what drives or exacerbates every major global problem is, ultimately, population growth. So whatever most effectively limits population growth is the greatest invention-and that's the pill, or contraception more generally.

As a researcher I believe that my most important contributions are inherent in the younger people I have worked with and in the increase of the universal knowledge that has resulted from the work that I have done and have sponsored among universities and companies.

Stephen Budiansky points to importance of "the domestication of the horse as a mount." The amazing fact is that mankind can learn new technology at an amazing pace. Thus, in a relatively short time after the introduction of the horse to America, the Apache were a great light cavalry. I would also agree with David Shaw re: "the steady accrual of both knowledge and technology that has accompanied the rigorous application of the scientific method over a surprisingly small number of human generations "; and with Stanislas Dehaene on the "concept of education."

So I guess my invention violates the 2000 year (very Christian limit). It is the intergenerational passing of information.

The kind of thinking that makes it possible for all these people to expound upon "the single most important invention of the last two thousand years" is the most important invention of the past two thousand years. There is no such thing as the single most important invention of the last two thousand years. The evolution of technology doesn't work like that. It's a web of ideas, not a zero-sum game.

Knowing how to turn knowledge into power is the most powerful form of knowledge. The mindsets, mindtools, and institutions that make massive technological progress possible are all part of an invisible cultural system — it is learned, not inherent, it was invented, not evolved, it hypnotizes you to see the world in a certain way.

What we know as "technology" the visible stuff that hums and glows — is only the physical manifestation of a specific kind of social system. That invisible system, which emerged over the past three centuries — what Jacques Ellul called "la technique" and Lewis Mumford called "technics" — is more important than all the inventions it engendered.

Do we lack one important invention at a crucial time when our inventions are becoming our only evolutionary competitor? We haven't formulated and agreed upon a way of making good decisions about the powerful technologies we're so good at creating. We have a lot of the knowledge that turns knowledge into power. We need more of the wisdom that knows what we ought to do with the power of invention.

Surely one of the most powerful earthly inventions has been the ability to represent any phenomenon with numbers — either analogue or digital — and then use this representation to predict outcomes in the real world. This information revolution actually began before the year zero with the Pythagoreans and has advanced through stages that include the invention of calculus and, most recently, boolean algebra and all the advantages of digital modeling.

And just as important has been the recent humbling realization that there are limits to this scientific cartography; that, tempting as it is, the map can never be mistaken for the real thing.

Inventions. My top runners in the area of physical inventions would have to be ways of harnessing energy, ways of moving around the world, and ways of communicating. And since the latter two depend on the first, I'd have to put my money on energy control and use.

But we've got lots of psychological and social inventions as well. I'd put the idea that all people are equal at the top of the list. This is an invention that we could make better use of.

Discovery of Childhood and Invention of Universal Schooling

Instead of suggesting a device, I nominate the educational process essential for a high velocity of inventiveness, the evolution of a technological society, and the spread of culture. While schools for the elite have existed since antiquity, the recognition of childhood as a unique time of life with special schooling, social, and emotional needs, and different standards of justice, is relatively recent and associated with Rousseau, Freud, Piaget, and their forbearers.

The discovery that children are not "miniature adults" led to a more humane society and was essential to tailoring educational programs to the developmental stage of the student. Universal schooling (and even the modern university) were born both of this increased appreciation of the special needs of children and necessity — the industrial revolution needed a cadre of trained workers, scientists and engineers. The complexity of modern technology and the associated acceleration of innovation demand a critical mass of creative minds and hands that cannot be provided by occasional virtuosi toiling in solitude.

If by invention we mean actual technological advances — as opposed to ideas, theories and concepts — then there have been some good ones. One thinks of the printing press and the clock, for example. It is too early to say for sure but my choice for the most important invention of the past 2000 years would be the invention of the set of agricultural techniques known collectively as "The Green Revolution". This invention began in the 1960's and continues into the nineties, indeed, it is now being extended into something that may well come to be called "The Green-Blue Revolution", which would extend new agricultural techniques to the oceans.

The most important invention of all time is the Neolithic Revolution. With the Neolithic Revolution, humanity found ways to grow crops systematically, and thus overcame both the instability and the fragility of life itself that went with hunter-gatherer ways of survival. Hunter-gatherers could neither stay in one place long enough to develop a stable civilization, nor could they count on being able to survive periods of drought and other forms of natural catastrophe. With the Neolithic revolution, both of these problems were solved, and civilization became a real possibility.

However the Neolithic Revolution brought problems of its own. In particular, the Malthusian problem, because the growth of population was constantly threatening to outrun the growth of food supply. For the foreseeable future, at least, this problem has been solved by the Green Revolution. The food supply has vastly outrun the increase in population. At this time, if you read that there is a famine going on in some part of Africa or Asia, you know that it is deliberately politically created. There is no international shortage of food. There is plenty of food to go around, and because of the Green Revolution, there will be food to go around for the foreseeable future.

The most important invention, I believe, was a mathematical idea, which is the notion of representation: that one system of relationships, whether mathematical or physical, can be captured faithfully by another.

The first full use of the idea of a representation was the analytic geometry of Descartes, which is based on the discovery of a precise relationship between two different kinds of mathematical objects, in this case, numbers and geometry. This correspondence made it possible to formulate general questions about geometrical figures in terms of numbers and functions, and when people had learned to answer these questions they had invented the calculus. By now we have understood that it is nothing other than the existence of such relationships between systems of relations that gives mathematics its real power. Many of the most important mathematical developments of the present century, such as algebraic topology, differential geometry, representation theory and algebraic geometry come from the discovery of such relationships, of which Descartes analytic geometry was only the first example. The most profound developments in present mathematics and theoretical physics are all based on the notion of a representation, which is the general term we use for a way to code one set of mathematical relationships in terms of another. There is even a branch of mathematics whose subject is the study of correspondences between different mathematical systems, which is called category theory. According to some of its developers, mathematics is at its root nothing but the study of such relationships, and for many working mathematics, category theory has replaced set theory as the foundational language within which all mathematics is expressed.

Moreover, once it was understood that one mathematical system can represent another, the door was open to wondering if a mathematical system could represent a physical system, or vise versa. It was Kepler who first understood that the paths of the planets in the sky might form closed orbits, when looked at from the right reference point. This discovery of a correspondence between motion and geometry was far more profound than the Ptolemaic notion that the orbits were formed by the motion of circles on circles. Before Kepler, geometry may have played a role in the generation of motion, but only with Kepler do we have an attempt to represent the orbits themselves as geometrical figures. At the same time Galileo, by slowing motion down through the use of devices such as the pendulum and the inclined plane, realized that the motions of ordinary bodies could be represented by geometry. When combined with Descartes correspondence between geometry and number this made possible the spatialization of time, that is the representation of time and motion purely in terms of geometry. This not only made Newtonian physics possible, it is of course what we do every time we graph the motion of a body or the change of some quantity in time. It also made it possible, for the first time, to build clocks accurate enough to capture the motion of terrestrial, rather than celestial, bodies.

The next step in the discovery of correspondences between mathematical and physical systems of relations came with devices for representing logical operations in terms of physical motions. This idea was realized early in mechanical calculators and logic engines, but of course came into its own with the invention of the modern computer.

But the final step in the process began by Descartes analytic geometry was the discovery that if a physical system could represent a mathematical system, then one physical system might represent another. Thus, sequences of electrical pulses can represent sound waves, or pictures, and all of these can be represented by electromagnetic waves. Thus we have telecommunications, certainly among the most important inventions in its own right, which cannot even be conceived of without some notion of the representation of one system by another.

Telecommunications also gave rise to a question, which is what is it that remains the same when a signal is translated from sound waves to electrical impulses or electromagnetic waves. We have a name for the answer, it is information, but I do not have the impression that we really understand its implications. For example, using this concept some people are claiming that not only is it the case that some physical or mathematical systems can be represented in terms of another but that, there is some coding that would permit every sufficiently complicated physical or mathematical system to be represented in terms of any other. This of course, brings us back to Descartes, who wanted to understand the relationship between the mind and the brain. Certainly the concept of information is not the whole answer, but it does gives us a language in which to ask the question that was not available to Descartes. Nevertheless, without his first discovery of a correspondence between two systems of relations, we would not only lack the possibility of talking about information, we would not have most of mathematics, we would not have telecommunications and we would not have the computer. This the notion of a representation is not only the most important mathematical invention, it is the idea that made it possible to conceive of many of the other important inventions of the last few centuries.

My nominee is the concept of evolution by selection (which encompasses natural selection, sexual selection, and the selective processes that generate cultural evolution). It offers the best explanation for what we are, where we came from, and the nature of life in the rest of the universe. It also explains why we invent and why we believe the inventions described in this list are important. It is the invention that explains invention.

I nominate waterworks — the system of plumbing and sewers that gets clean water to us and dirty water away from us. I'm hard pressed to think of any other single invention that has stopped so much disease and death. It may not inspire quite the intellectual awe as something like a quantum computer, but the sheer heft of the benefits it brings about so simply makes it all the more impressive. John Snow didn't need to sequence the Vibrio cholerae genome to stop people from dying in London in 1854 — he didn't even know what V. cholerae was — but a pattern of deaths showed him that to stop a cholera outbreak all he needed to do was shut down a fouled well. Without waterworks, the crowded conditions of the modern world would be utterly insupportable — and you only have to go to a poor city without clean water to see this. Another sign of the importance of an invention is the havoc it can wreak, and waterworks score here again—by cutting down infant mortality they help fuel the population explosion, and they also let places like Las Vegas suck the surrounding land dry.

I'd even go so far as to put the importance of the invention of waterworks on an evolutionary scale with things such as language. For hundreds of millions of years, life on land has been crafting new ways to extract and hold onto water. With plumbing, however, you don't go to the water — the water comes to you.

Over 4.6 billion years, the most important evolutionary inventions have been those that code, store, and use information in new ways. DNA; nervous systems; organic devices enabling cultural transmission of information. In large perspective, the most important invention over the past 2 thousand years will likely be something related to computers, electronic information coded and handled outside of living bodies. Its importance, however, has not yet been fully realized. I'm going with something whose impact so far is more apparent. The paleontologist in me wants to say something like the discovery of time — from inventions that have led to an intense sense of personal time to others that have found out the age of the universe or the human species. These inventions are perception-altering. But there's another invention with greater impact. My vote is for flying machines.

Before 2 thousand years ago, sea craft allowed the overcoming of water; the wheel, the conquest of earth. And now flying machines, the conquest of air — an invention that taps into the center of our mythologies.

Many inventions change our lives but stay in the predictable range of human nature. Firearms, for example, have had their impact mainly by extending existing tendencies to bluff, subjugate, or kill in immediate, face-to-face situations. Air craft have altered our perceptions in ways that were evolutionarily unpredictable. They changed the delivery of weapons, vastly destructive weapons, to a inter-continental scale — a wholly new scale, unprecedented in evolutionary history. A flu virus that mutates in Kennedy Airport is spread around the world within a day or two. And so the history of disease has been altered by moving the month- or year-long dispersal of disease to a time scale of hours.

We now meet other people en masse anywhere in the world in less than a day's travel. Thus things foreign and strange have become familiar. Ancient phobias and bias toward hatred and exclusion have been altered widely. The CNN culture (instantaneous worldwide information) is an extension of this; in my view, the actual intermingling of people from one place to another has been the more important, precedent-shattering development. Despite international information media, civil strife remains the worst where cultural and physical insularity reigns.

Finally, flying machines have meant a global altering of how societies approach food and other resources, tying humanity together in a worldwide economy (resource exchange) driven by our interdependence. Two million years ago, the movement of resources (like food and stone tools) had become a development with extraordinary implications for human evolution. But even 2 thousand years ago, no one could have foreseen just how far this process of resource exchange has gone today — largely due to flying machines.

BOARD GAMES

Board games, more than any other invention, foretell the role of science in understanding the universe through symbolic reasoning. Their essence is a simple set of rules for generating a complex network of possibilities by manipulating tokens on a reticulate board.

Board games are found as artifacts of the earliest Egyptian dynasties, so they don't truly fall within the 2000 year limit, but they have undergone a rapid "adaptive radiation" in the last millennium. Thales' invention of logic (the manipulation of abstract tokens under fixed rules) was likely influenced by a knowledge of board games, and board games offered an early metaphoric guide for politics and war in both the East (Go) and the West (Chess). These insights, in turn, had much to do with transition from the belief that the world around us is controlled by the whims and personalities of gods to the outlook that the world can be described in lawlike fashion. In the 19th and 20th centuries board games became the inspiration for models, simulations and mathematics, ranging from genetics and evolution to markets and social interaction. Board games also offer a simple example of the recondite phenomenon called emergence — "much coming from little" — as when a fertilized egg yields a complex organism consisting of tens of billions of cells. And, via a mutation into video-games, board games offer the next generation an entry into the world of long horizons and rigorous thought — both in short supply in the current generation.

Summary answer: The non-implemented 33-year English Protestant Calendar.

Let me start my answer by making a few comments about the suggestions made by other correspondents, and the general premise of the specific answer I give myself.

At the time of writing many answers are already in, and so many good ideas have been aired. I don't even need to refer to the list to guess at some of them: the computer, the contraceptive pill, gunpowder, the internal combustion engine, nuclear weapons. Wait! you say. What am I suggesting, that nuclear explosions are good? Well, maybe not from the perspective of how they may be used on Earth; but from another perspective one could claim that they have been a major peacekeeping influence over the past half-century, which has been comparatively war less compared with what one might have expected given the other technologies available: jet planes, napalm, guided missiles,... Note that I wrote "one could claim" — that does not mean that I am claiming it, I am just posing an arguable position.

In the same way one could argue that the contraceptive pill, which has indeed been nominated as one of the most important inventions, is actually a bad thing. For example, we cannot know whether it has robbed us of a 21st century Einstein who would have found the way to unify the laws of physics whilst identifying a cure for cancer in her spare time.

The impossibility of knowing how the world might have been post hoc opens up various avenues of thought, like what if Hitler had never lived? (a matter explored in certain ways by Stephen Fry in his novel 'Making History'). Obviously this has a wide variety of implications with gross repercussions, especially for the Jews, Gypsies and other races which were the target of such atrocities. But for my present purposes let me sidestep such huge considerations, and instead look at some trivial ones. Suppose that you are the President of the Boston and Area Volkswagen Beetle Owners Club: you might adjudge the hypothesized nonexistence of Hitler as being most important in your life because the Beetle would never have been built.

One therefore has to think about what important means in the context of different people's lives. Right now the most important thing to a Denver Broncos fan (I write as they stand 13-0) is whether a perfect season is in the offing. Excuse me but isn't that totally insignificant to some starving child in Ethiopia; but it is the thing foremost in the mind of that Broncos fan, perhaps fatally-so: he may crash whilst driving to the next game at Mile High Stadium and lose his life, never getting to see his team romp the Superbowl again.

The outcome of my own mental perambulations on this question of the most important invention is that all the technological products, of recent years and old, would not only have been invented sooner-or-later anyway, but also they are mere applications of ideas. An idea may be important, even though it does not directly lead to an important invention with a physical reality. An idea itself I count as being an invention in the current context.

Further, how we got to where we are now is the result of many important ideas producing branching points in history. Now, one could make a case for the more distant (in history) branching points being more fundamental, because all following events depend upon them. If Alexander the Great, Charlemagne and William the Conqueror had never lived, then neither would Hitler. But that form of reasoning leads to a reductio ad absurdum.

Rather, I choose to ask: "How did we get to where we are now?" The first step needed there is to define where we are, and the answer to that is: with the USA being the powerhouse of most of the rest of the world. Thus the branching point I look to is that which made the USA a reality. I do not mean the Declaration of Independence. I mean: what made the English first go and settle the Atlantic seaboard of North America?

The answer to that provides my answer to the "Most Important Invention In The Past Two Thousand Years", but it is not original to me. The thing I am going to describe was suggested to me by Simon Cassidy, a British mathematician who lives in California.

Here is the story. When the Catholic Church (per Pope Gregory XIII) brought in the reformed calendar in 1582, they decided to use a second-best solution to the problem. Let me tell you, all Christian calendar matters hinge on the question of the Easter computus. That depends upon the time of the vernal equinox, which is ecclesiastically defined to be March 21st, although astronomically-speaking the equinox on the Gregorian calendar shifts over the 400-year leap-year cycle by 53 hours, between March 19 and 21. This follows from the long cycle time.

By far preferable from a religious perspective would be a calendar which keeps the equinox on one day, requiring a shorter cycle. Even so far back as AD 1079, Omar Khayyam had shown that an eight leap-years in 33-year cycle provides an excellent approximation to the year as measured as the time between vernal equinoxes. The advisers of Gregory XIII knew this but instead recommended the inferior 97/400 leap-year system we use, perhaps in the belief that the Protestants did not know of the better 8/33 concept.

But in England, they did. John Dee and others (Thomas Harriot and Walter Raleigh amongst them) had secretly come up with a plan to implement a 'Perfect Christian Calendar' using the 33-year cycle (the traditional lifetime of Christ). In that span there are eight four-year cycles leading to a time-of-day wander by the equinox of just below 18 hours. The problem is the one five-year cycle in each grand cycle, during which the equinox steps forward by just below six hours in each of four jumps before the following leap year pulls it back by 24 hours. The full amplitude of the movement is 23 hours and 16 minutes. To get the equinox to remain on one calendar day throughout the 33-year cycle one has to use as a prime meridian for time-keeping a longitude band which is just right, and quite narrow. It happened (in the late sixteenth century but with movement east since due to the slow-down of the Earth's spin) to be at 77 degrees west, which Cassidy terms "God's Longitude".

If you look down that meridian you will find that in the 1580s the settled areas (in the Caribbean, Peru, etc.) were under Spanish, hence Catholic, control. To grab part of God's Longitude and found a New Albion, enabling them to introduce a rival calendar — that Perfect Christian Calendar — and convert the other Christian states to the Protestant side, England mounted various expeditions which historians have since misinterpreted. In 1584-90 the so-called Lost Colony was sent to Roanoke Island, a bizarre place to attempt to start colonization but an excellent site from which to make astronomical observations to fix the longitude and thus decide how far inland New Albion should be. Similarly in 1607 the choice of Jamestown Island seems bizarre from the settlement perspective — why not out on Chesapeake Bay, and away from the attacks of the local Algonquians led by Pocahontas' father Powhatan? — but makes sense from the paramount need to grab a piece of God's Longitude. From the foothold the English managed to gain, Old Virginny grew and later other colonizers came to New England, and New Amsterdam was bought from the Dutch. But later utility/developments do not reflect the original purpose of the English coming to Roanoke Island and Jamestown Island any more than the Eiffel Tower was built to provide a mount for the many radio antennas which now festoon its apex.

After the fact the English did not reveal their prime motivation for Raleigh's American adventures and the investment in the ill-starred Jamestown colonizers, and all of this is yet to be properly teased out. But if the English had never invented their non-implemented 33-year Protestant Calendar, then the USA as it is would not exist, and all of the scientific, technological and cultural development of the world over the past couple of centuries would be quite different. In view of this I nominate that calendar, due to John Dee, as the mostimportant invention of the past 2000 years.

The most important invention is the idea of continued scientific and technological progress. The individual who deserves the most credit for this is Francis Bacon. Before Bacon progress occurred but was sporadic, and most people did not expect to see new inventions in their lifetimes. The idea of continued scientific progress became institutionalized in the Academei dei Lincei, the Royal Society and other scientific academies. the idea of continued invention was institutionalized with the patent laws.

Thanks for your invitation (and for your project in general). I'd respond more fully but the question seems too ill-defined to answer. (I guess I still have something of the reductionistic, literal mindset of a mathematician despite periodic forays into more nebulous realms.) An invention or innovation that becomes essential has a tendency also to become invisible as we, in a sense, "grow around" it. If I were forced to name something, I guess I would go with Gutenberg's movable type. And if I wanted to be puerilely self-referential, my choice for most important invention might be the notion of a precise question. (Nevertheless, I do see the value of vague ones as well.)

DIGITAL ECOSYSTEMS

A digital ecosystem is a kind of universe, realized in electronic media, in which we observe incremental evolution and complex interaction. The classic examples come from work in Artificial Life, such as Tom Ray'sTierra project in which strings of code compete for resources, such as CPU time, and in which cascades of strategies for success develop, with later ones exploiting the weaknesses and loopholes of their predecessors.

But the idea is much broader. The worldwide web and browser technologies have combined to create a massive digital ecosystem populated by ideas and product descriptions, whose true impact on the human lifestyle is only just beginning to be felt. The human mind was never contained in the head, and has always been a construct involving head, artifacts (such as pen and paper), and webs of communication and interaction. We make our worlds smart so that brains like ours can be dumb in peace. But the development of web and internet technologies may well signal the next great leap in the evolution of thought and reason. For we now have a medium in which ideas can travel, mutate, recombine and propagate with unprecedented ease and (increasingly) across the old barriers of culture, language, geography and central authority.

Moreover, and in a kind of golden loop, we can use our experience with more restricted digital ecosystems to improve our grip on the properties of the kind of large, distributed, self-organizing system of which we are now a proper part. Understanding these properties is important both for policy making (what kind of regulation creates and maintains the optimal conditions for productive self-organization in a complex and highly uncertain world?) and for moral and economic reason. Human brains are bad at seeing the patterns that will result from multiple, ongoing, bidirectional interactions: see, for example, the simulations that show, to most peoples surprise, that if each person in a group insists on having just 30% of their neighbors 'the same' as them (picked out by race, gender, sexual inclination or whatever you like), that over a short period of time what evolves is a highly segregated ecology containing a great many 'all X' neighborhoods. Perhaps if our children get to play with quite large-scale digital ecosystems, in games such as Sim City or using new educational resources such as such as Mitchell Resnick's Starlogo, they may yet learn something of how to predict, understand, and sometimes avoid, such emergent patterns.

Digital ecosystems thus both radically transform the space in which human brains think and reason, and provide opportunities to help us learn to reason betterabout the kind of complex system of which we are now a part. The double-whammy gets my vote.

I will cast my vote for anaesthesia. While this invention may not have changed the world for all, it has certainly altered the lives of many for the good. Imagine a world without anaesthesia. It makes me shudder.

Howard Gardner and I are probably one of the few couples who replied to your request. Last night we were at a party and we mentioned this project. I said that Howard's and my choices (Western classical music, Howard; vs. anaesthesia, Ellen) showed how different we were, Howard the optimist, I the one who thinks of the grim side of life. At the party was Yo Yo Ma, who listened with interest and said, without skipping a beat, that our two choices were not so different, because "One is a form of the other." (Interpret that as you will “ I take it to mean that music is the ultimate escape from pain, but also perhaps that anaesthesia [when needed] is as pleasurable as music).

My instantaneous response was: Gutenberg's printing press with movable type. This knee-jerk response was followed by a pause and reflection.

What is meant by "invention"? So, to the dictionary! Essentially, anything that did not exist previously, whether it be a mechanical device or art,literature,or music, is an "invention". Sobered by this, I reflected again.

The skulls of l0 skeletons found in Skhul Cave at the foot of Mt. Carmel in Israel in the l930's are similar in size and shape to modern Homo sapiens. These have been dated at 80,000 years. A similar skull found in a cave at Qafzeh, Israel has been dated at 9l,000 years. Having the same size brain capacity, of course, does not necessarily mean they had our same intelligence, although they were capable of making beautiful stone tools.

We jump now to the Chevaux cave in France, where wall paintings of animals extant in Europe at that time are beautifully depicted and have been dated at over 30,000 years. l5,000 years later in the caves at Le Portel and Lascaux in France, our ancestors were making magnificent polychrome paintings of animals. Their stone tools at that time and for the previous 5,000 years are comparable in technique and beauty to any made by Native Americans in the past few hundred years.

Can anyone doubt that these Cro-Magnons could have learned to read and write, to philosophise, to do math at a high level, to learn chemistry and physics if magically brought into our culture of today? (Let's leave out some fundamentalists who still don't believe in evolution.)

We find that cuneiform writing began about 5,000 years ago and quickly evolved. By 2,500 years ago, the Greeks were producing masterpieces of plays, literature, art, architecture, and they were doing some wonderful things in mathematics and elementary observational science. The Romans carried on these traditions until their fall. Christianity came in and destroyed as much as it could of this great heritage in western Europe including the great library in Alexandria.

Thus began the "Dark Ages" in Europe. The gradual dissemination of knowledge, other than ecumenical literature (which wasn't much faster!) was extremely slow. So, in the mid fourteen hundreds along comes Gutenberg with his printing press and its movable type. Of course, almost the first thing he did was print a bible or two and they sold like hot cakes. True, fixed or non movable type had been around for a short time, but the process wasn't much faster than printing books by hand and was very costly, so, the rapid dissemination of knowledge through printed books began with Gutenberg.

While it is true that the Dark Ages began to end about the year l,000, real progress wasn't made until the Renaissance and, particularly, with the rapid dissemination of knowledge via Gutenberg-type presses. As books were published, people became inspired to learn to read. Reading led to thinking about what had been read and to further publications and to communications between people. The first world wide web had been started, Anyone with a grain of sense can see what this has led to!

So, John, after my consideration outlined above, I still think the Gutenberg press with movable type is the greatest invention of the past 2,000 years or, perhaps of the last 5,000 years after cuneiform writing was invented!

Science, because it brings us explanations of our world we may act on, is by far the most important invention of this time. The fact that the explanations are usually wrong brings the partial illusion of progress, as well as tenure, which is a consequence of the publications debating the various wrongnesses.

At its best, science works in a sort of Darwinian frame, where hypotheses are the source of variation (cleverness counts) and disproofs are the extinctions.

Developments from hypotheses are the analogues of ontogeny, and there are various other processes that parallel the biological world such as the roles of randomness (first publications carry excess influence by virtue of being first, just as Microsoft systems succeed by being most common but not necessarily best), and punctuated equilibrium (scientific revolutions are complete replacement events). There are even biological-like terms like "memes" that may describe how hypotheses are transmitted. All and all, ever since when well before Neandertal times we hominids developed significantly complex culture, that extrasomatic way of transmitting hierarchically structured information, we have enjoyed (in the sense of the Chinese curse) interesting times.

Last year, I held my tongue when it came to questions. No one however asked directly as I recall what was most important to me. What is going to happen to me after I die? This is only the prologue to other questions that go to a root of human consciousness for me, is there order or no order in the universe? If there is order does it represent in my own life a pattern that is supposed to mean something for me. What meaning does my life have? Is there order or simply random event in my life? Does what I do effect the order of the universe in any important way, in any way that effects its order?

According to the scholar of religious philosophy Harry Wolfson, Spinoza believed that memory would survive, though he had no logical proof for this belief. Human actions would therefore matter because they would be bound up with memory. Evolution and DNA in part confirm that at least in limited spans of time this is true. What will survive me? What is most important in the last two thousand years, I feel is the human capacity to enact symbols, to identify reality with them.

A friend who is both a distinguished mathematician and a rabbi, likes to quote Maimonides to the effect that only original thoughts will survive in the after life. This is after all, a consoling thought to a mathematician, since "original thoughts" are the métier of the sciences. And it is with "fear and trembling" that I tread through the gates of EDGE site on the sacred ground of scientists.

As a novelist however, I beg to differ with the particulars of this hope, for originality is not necessarily important in the world of fantasy or rather what is compelling is not necessarily what is most original. The very word "invention" has in some of the early responses, a scientific, or pseudoscientific interpretation. I believe (as someone who has seen briefly — though in a state of such high anxiety I can readily admit — they may have been hallucinations — ghosts), that the act of symbolic enactment is a key to the riddle of consciousness and the most important of human "inventions." Nor do I think such "enactment" or symbol drama is entirely a "human" invention. For I believe I derives from play, though in human beings it has come to combine play with the self reference of thought about existence. The latter drama of symbols I think it is part of the uncanny tension between the weight of the Unknown (which I choose to personify with a Capital) and consciousness.

The story that has historically "galvanized" Jewish thought and then Christian thought is the Biblical saga of the sacrifice of Isaac, where a family or tribe obviously familiar with human sacrifice, passed to its symbolic enactment. In the Sinai desert, years ago, a German sociologist, Gunnar Heinneson, told me that the Jews were the first people to do away with the exposure of unwanted infants. You can speak volumes about human values, but without ceremonies that address terror of the Unknown, the human majority falls prey to the overwhelming anxiety of death and its handmaiden, survival.

I am not enough of a historian or anthropologist, to insist on what Gunnar spoke of as fact. Symbolic enactment obviously goes much further back in human history than the Biblical world in which we have idealized patriarchs and matriarchs. It probably derives from the play that we can observe among animals. It is however, a process that is constantly being refined. I can appreciate that the Sioux Indians when they knocked an opponent on the head with a stick rather than killing him, also invented something that civilization needs — an extension that the rage for national sports teams may well answer. We recognize, I think, as a society that feels that peace with ourselves is important, that exposing children who are actually delivered, on door steps, brutalizes us as a people of shared customs.

Steven Rose speaks of inventions as concepts. It is in bringing ourselves back, again and again, to the concept of invention and in particular of the invention of symbol in the light of our fear, that I think both the human body and mind find themselves in a balance that allows them to experience that mysterious state that Plato called the "good" and the Bible referred to as "completed" or "perfect": or "quiet within oneself."

I would challenge Colin Blakemore's assertion that control of human destiny has shifted from the body to the mind. The mind after all is finally subject within the human span to the body, just as the latter has no conscious existence without the mind. We have to reinvent a form of the Shamanism that seeks to bridge this division within contemporary religion or suffer a terror that will devastate most of us in mind and body. When we seek overwhelming joy, in sex, art, music, even the pursuit of knowledge, or understanding, some of us are asking to be just that, overwhelmed through the mind but throughout the body and that has to be part of my "greater good" or "balance." At Thanksgiving dinner, two prominent friends in the lofty upper spheres of the university were mocking the blessing of human organs as they passed to the recipient. I felt the opposite, that in the bleak sphere of the hospital, it might be important to a system in shock. The symbol dramatized recalls inspired pages of Milosz on the dance and the way movement locates us in the universe.

Space grows bleak without a sense of this location and dangerous in its suggestion of no meaning. I think we need a more powerful sense of symbol if we are to avoid the fear that our very mastery of technological invention spurs. If human sacrifice was found to be unnecessary, so could heroic distinction based on war, national identity based on exclusion, social identity based on wealth, even the more exaggerated rewards of entrepreneurship, great wealth. Some years ago I suggested (in the "Village Voice") that the Israelis and Palestinians could find a lasting peace if they both acknowledged large parts of what is called "Israel," what is called "the West Bank," even what is called "Jordan," in other words, Biblical Canaan, as sacred space and turned what was still empty into religious park. Tragically, their statesmen can not invent such a symbolic space.

To answer Colin Blakemore, I certainly found the contraceptive pill a liberation, at first. Soon, however, it seemed to confuse some of the deepest impulses of sexual joy. I am not sure that the puritanical strategies of the 19th century in which eroticism was buried in passionate friendship were not more effective as symbolic of the desire to be one with another than sex in which no children were intended or hoped for. I would never want to go back to a world without the pill or effective contraceptives, but I am not sure we have mastered its implications for the body or the mind in that body. For the pill has no ceremony, no weight of ritual behind it and the meaning of its communion still awaits definition.

I am afraid the answer I find compelling is a rather trivial one. The two most important inventions in the past two thousand years are the computer and the atomic bomb. The computer will bring about the greatest change to human life since the neolithic revolution, unless the bomb destroys human life altogether.

I would have to agree that Gutenberg's printing press is the most important invention in the past two thousand years because it changed forever the cost of knowledge distribution. What other inventions wouldn't have happened if the inventor didn't have access to books? In a sense I think we can trace many aspects of our information society back to this single invention. In it's electronic form on the web we see movable type and a yearning for information to be accessible and free. The web is taking the cost of distributing information down near zero. Gutenberg would be pleased to see where his invention has taken us.

THE MIRROR

The most influential invention in the past 2000 years has been the mirror: It has shown to each person how she or he appears to other persons on the planet. Before the widespread production and use of mirrors that came about in the Renaissance, humans could mirror themselves in lakes and metallic surfaces. But only with the installation of mirrors in everyday life did viewing oneself from the outside become a daily habit. This coincided with the advent of manners for eating, clothing and behaving. This again made possible the modern version of self-consciousness: Viewing oneself through the eyes of others, rather than just from the inside or through the eyes of God.

Hence, consciousness as we know it is an effect of an advanced mental task: To acknowledge the person experienced out there in the mirror as the same as the one being simultaneously experienced from within. To know that the person out there in the mirror is controlled by me in here. The invention of the mirror is closely related to the problem of free will and to the invention of the modern human ego as described in this poll by Jaron Lanier.

The problem with overemphasis of conscious control is thus the problem of supervising oneself through the eyes of others, rather than just acting out. Many malaises of modern life stems from the fact that one tends to consider the mirror-image of oneself as more real than the view from within.

This new loop of the-outside-person-viewed-by-the-inside-person recently got a parallel with the first images of the Earth seen on the sky of the Moon: No longer just the planet we can touch and live on, the Earth became a heavenly body comparable to other celestial objects.

If it had not been invented over three thousand years ago, I should have nominated the bell, but instead I choose the symphony orchestra. This is because, like the bell, it establishes a dramatic link between two seemingly disparate worlds — the material world of science and the world of the psyche and the arts. The symphony orchestra is surely important because it made possible classical music, the nomination of Howard Gardner. However, I choose it as a symbol for something that may yet be to come, like space travel, the choice of Reuben Hersh. What is more, I make my choice precisely because in just one point I disagree with Howard Gardner — classical music is crucially dependent on physical inventions: musical instruments. I have long been fascinated by one of the great conundrums of philosophy that was clearly recognized by Newton's contempories: If there is only a material world characterized by the so-called primary qualities such as extension, motion, and mass, how are we to explain our awareness of so many different secondary qualities such as colors, sounds, tastes, and smells? The material world has no need of them and can never explain them. Of course, we all know that science can now demonstrate how specific sensations are correlated with physical phenomena, but a correlation is not necessarily a cause — for both correlates may have a common cause — and still less is it an explanation. How can the vibrations of cat gut create in me the effect I experience when listening to Beethoven's quartets? Perhaps I am naïve, but I am a committed scientist. I cannot be content to regard the secondary qualities as epiphenomena. I think there could be a physics, far richer than the one we presently know, in which the secondary qualities are as real as electric charge. The bell and symphony orchestra call us to ponder higher things and wider possibilities, the domain where science is reconciled with the arts.

Philip Anderson asks the right question: "Why has no one mentioned the printing press yet?"

I mean, doesn't it seem kind of obvious that printing — under which would be subsumed all forms of large-scale reproduction of the written word, from handmade wooden type to the computer and word-processing program I'm using to write this — was the most important invention of the past two thousand years? Printing led directly to mass literacy, democracy, the scientific revolution, cyberthis and cyberthat, and all those other good things.

A more general observation. I notice that most of the responses you included in the email suggest that the most important invention of the past two thousand years, whatever it was, just happens to have happened in the past hundred years. Doesn't this reflect a bad case of chronocentrism, i.e., the irrational belief that one is lucky enough to be living in history's most important era? Given that people have been inventing things all along, isn't it unlikely that all the most important inventions would have happened in one little century out of twenty? Wouldn't it be more logical to expect them to be spaced out randomly over all twenty? Even if the twentieth is a particularly inventive century, isn't it a little myopic to imagine that the one we just happen to be living in is twenty times more inventive than any of the others? Maybe four or five times more inventive, but even that would be a stretch.

Interesting question. My candidate would be: The concept of information as a commodity, a thing that can be bought and sold. It's an ancient invention, dating back to the day of the fleet footed messenger, but its enormous consequences had to wait for the acceleration of information-carrying technologies like the telegraph and the Internet. We're only now witnessing the cumulative impact, as the buying and selling of information begins to outweigh the buying and selling of stuff.

Why is this so important? Because humans who trade in information behave like our hunter gathering ancestors. They are alert and adaptable to an ever-changing environment. They work in small groups. They are independent thinkers who dislike taking orders and are fervently egalitarian. They place their faith in face to face relationships, not authority or a title. For as long as humanity got its living by agriculture or industry, such traits had to be suppressed in favor of those more amenable to centralization, authority, large-scale enterprises. This epoch is coming to an end. In the post-industrial west we no longer value stability, steadfastness and predictability over change, adaptability and flexibility. We are no longer awed by political power, instead seeing those who hold it as just like us. (When I was a kid people worried about the ``Imperial Presidency'' becoming too awesome for a democracy to support. But then, when I was a kid, an ex-wrestler could not get elected governor of Minnesota.) Corporate types often remark that their 20-something employees can't take orders and expect to be able to dress as they please and bring their parrot to work.

All this is supposed to be a consequence of prosperity. But it seems to me the shift is far more profound. After a 7000-year detour through agriculture and industry, we are returning to the ways of our proud, individualistic, headstrong, small-group-dwelling forebears, and that will reshape the human community profoundly. And it's the move from a thing-economy to an information-economy that's making it happen.

In the spirit of completeness and risking chronocentrism big time, I nominate Public Key Cryptosystems as something invented during the last two thousand years and which will remain useful long after the printing press will exist only in the (electronic) history books next to the steam engine. PKC has three incredible properties: perfect privacy, perfect authentication, and a reliable carrier of value and contracts — like gold used to be. All this in the digital environment where information can be easily and perfectly stored and copied. At a single stroke PKC transformed our vision of the asymptotic result of information technology from the 1984-ish nightmare to a realistic and ultimately attractive cyberspace where identity and privacy are not lost, despite of our (and Orwell's) commonsense intuition to the contrary.

THE SPECTROSCOPE

The telescope resolves light from very far away. The spectroscope analyses and diagnoses it. It is through spectroscopy that we know what the stars are made of. The spectroscope shows us that the universe is expanding and the galaxies receding; that time had a beginning, and when; that other stars are like the sun in having planets where life might evolve.

In 1835, Auguste Comte, the French philosopher and founder of sociology, said of the stars:

"We shall never be able to study, by any method, their chemical composition or their mineralogical structure . . . Our positive knowledge of stars is necessarily limited to their geometric and mechanical phenomena."

Even as he wrote, the Fraunhofer lines had been discovered: those exquisitely fine barcodes precisely positioned across the spectrum; those telltale fingerprints of the elements. The spectroscopic barcodes enable us to do a chemical analysis of a distant star when, paradoxically (because it is so much closer), we cannot do the same for the moon — its light is all reflected sunlight and its barcodes those of the sun. The Hubble red shift, majestic signature of the expanding universe and the hot birth of time, is calibrated by the same Fraunhofer barcodes. Rhythmic recedings and approachings by stars, which betray the presence of planets, are detected by the spectroscope as oscillating red and blue shifts. The spectroscopic discovery that other stars have planets makes it much more likely that there is life elsewhere in the universe.

For me, the spectroscope has a poetic significance. Romantic poets saw the rainbow as a symbol of pure beauty, which could only be spoiled by scientific understanding. This thought famously prompted Keats in 1817 to toast "Newton's health and confusion to mathematics", and in 1820 inspired his well known lines:

"Philosophy will clip an Angel's wings,
Conquer all mysteries by rule and line, 
Empty the haunted air, and gnomed mine — 
Unweave a rainbow . . ."

Humanity's eyes have now been widened to see that the rainbow of visible light is only an infinitesimal slice of the full electromagnetic spectrum. Spectroscopy is unweaving the rainbow on a grand scale. If Keats had known what Newton's unweaving would lead to — the expansion of our human vision, inspired by the expanding universe — he could not have drunk that toast.

Okay, I'll bite. Has anyone nominated free will yet? The concept is more than 2,000 years old, but surely it deserves consideration as one of our most important inventions ever. Almost as soon as philosophers conceived of free will, they struggled to reconcile it with the materialistic, deterministic views of nature advanced by science. Epicurus insisted that there must be an element of randomness within nature that allows free will to exist. Lucretius called this randomness "the swerve." Modern free-willers find the swerve within chaos theory or quantum mechanics. None of these arguments are very convincing. Science has made it increasingly clear — to me, anyway — that free will is an illusion. But more even than God, it is a glorious, absolutely necessary illusion.

Birth control (or if you need it to be more specific, the pill)

Why? Because freedom from constant childbearing means that women can become meme-spreaders like men — working for their memes rather than their genes. This then means a change in the kinds of memes that propagate effectively, including all the memes of other inventions as well as the meme-spreading media, myths, science and the arts. In other words, it is important because it changes the whole of culture. Few single inventions have this effect on the whole meme pool.

Like others who have responded, I think the choice is obvious. The remarkable thing is that "the obvious choice" is different for everyone! To my mind, the most important inventions are those which have forced the largest changes in our world-view. On the basis of this criterion, I pick two (for reasons listed below): The telescope, and the theory of evolution by natural selection.

I pick two because it seems to me that there are two major categories of important inventions: a) complexity increasing, and b) complexity decreasing.

By complexity increasing, I mean those inventions that open up vast new realms of data, which can not be accounted for on the existing world view, making the universe less understandable, and therefore seemingly more complex.

By complexity decreasing, I mean those inventions that identify a pattern or algorithm in vast realms of data, ridding that data of a good deal of its apparent complication. These inventions force alterations to our world view to account for previously unaccountable data, or to account for it more directly and simply, making the universe more understandable, and therefore seemingly less complex.

The former tend to take the form of instruments or devices — physical constructs — while the latter tend to take the form of concepts, theories, or hypotheses — mental constructs. Both qualify as inventions.*

(*To be careful, the former also involves a mental construct — a device alone is useless without the mental construct that points it in the right direction.)

In the former category, nothing rivals the telescope.

No other device has initiated such a massive reconstruction of our world view. It forced us to accept the Earth, and ourselves, as "merely" a part of a larger cosmos. Of course, numerous theories besides the earth-centered universe existed before its invention, but the telescope opened the doors to the flood of data that would resolve what were previously largely philosophical disputes. The microscope — a relative of the telescope — also opened the door to a previously unimagined universe, and runs a close second to the telescope on the world-view shaking Richter scale.

In the latter category, there are many brilliant candidates, but I think that Darwin's invention of the theory of evolution by natural selection outshines them all. It is perhaps the only truly general theory in Biology, a field much more complex than physics. If we discover life elsewhere in the universe it is likely to be the only biological theory that will carry over from our terrestrial biology. Darwin's theory reduced tremendously the complication of zoological data. Critically, as with the telescope, it has put tremendous pressure on the previous world-view to accommodate man as "merely" a part of a much larger nature. This pressure is still largely being resisted, but the outcome is clear.

A close second would be the Second Law of Thermodynamics. Although the Second Law has not, perhaps, posed such a profound challenge to our collective world view, it has tremendously reduced the complexity of a great body of data (and it profoundly affects the world view of anyone who studies it in detail!)

I would have nominated the computer, but I think that, although it has profoundly affected our daily routines, it has not yet profoundly affected our world view. The computer is a kind of mathematical telescope, revealing to us a vast new realm of data about what kinds of dynamics follow from what sorts of rules — we are constantly discovering new galaxies of mathematical reality with computers. However, it will be a while before these empirical discoveries force a profound alteration of our world view.

My candidate would be the idea of the unconscious, the notion that what we say and do and feel can spring from sources of which we are not aware, that our choices and the qualities of our relationships are deeply motivated by our histories. In recent years, the Freudian contribution has tended be seen as historical...something we have passed beyond...but I think that in large part this is because the most fundamental ideas of psychodynamics have passed into popular culture as a given. These ideas animate out understandings of who we are with our families, with our friends and work. They add a dimension to our understandings of what it is to be human that will become increasingly important as we confront world in which artificial intelligences are increasingly presented to us and our children as candidates for dialogue and relationship (this year's Furbies are only a beginning) — and we are compelled to a new level of reflection about what is special about being a person.

The most important invention has been reading-glasses. They have effectively doubled the active life of everyone who reads or does fine work — and prevented the world being ruled by people under forty

My vote for "The Most Important Invention In the Past Two Thousand Years" is Gödel's Incompleteness Theorem. This single piece of mathematical jujitsu, proving unprovability, formally ended the strain of Western thought begun by Socrates and first fully fleshed out by Aristotle. The ancillary effects of that theory — a rejection of master narrative, an understanding that we will never know all the answers, an acceptance of contradiction, and an embrace of complexity — are just now making themselves felt in the dawn of the post complete world.

The most important invention in the past two thousand years?

In my opinion it is the invention by Otto von Guericke in 1660 of a machine which produced static electricity. This device was the primitive tool which unlocked our understanding and application of electricity. Modern power generation, communication, computation, and almost all of our most important analytic devices stand on the foundation of von Guericke's machine. A long line of basic intellectual formulations from electromagnetism to the bioelectric properties of brain mechanisms owe a debt to this invention. When we discover how the human brain creates the covert models of its own inventions, the structure and dynamics of the brain's own electrical activity will undoubtedly be an essential aspect of the explanation.

Technological advances in communication from clay tablets, to papyrus,to moveable type, to postscript have had a shaping influence on society and these are accelerating. Almost overnight, the accumulated knowledge of the world is crystallizing into a distributed digital archive.

Images and music as well as text have merged into a universal currency of information, the digital bit, which is my choice for the greatest discovery of the last two millennia. Unlike other forms of archival storage, bits are forever.

In the next millennium this digital archive will continue to expand, in ways we cannot yet imagine, greatly enhancing what a single human can accomplish in a lifetime, and what our culture can collectively discover about the world and ourselves.

I would have to vote for philosophical skepticism as the most important "invention" (if one thinks of invention as fabrication rather than discovery, as it is more archaically meant) of the past two thousand years. The notion that there is a "truth behind" things and a "bottom" to the matter has instilled in all of us, whether scientists, philosophers, theologians, or lay people, a maniacal obsession with improving our explanatory capabilities. As such skepticism can be seen as the driving force behind science and technology, modern conceptions of faith, the soul, and the other. Of course, one might argue that skepticism has been around for longer than two thousand years; but its characterization as a fundamental problem to be contended with before any constructive work can be done seems to me a peculiarly modern invention, a defining feature of our intensively self-conscious, post-Cartesian world.

I propose that the most important invention in the past two thousand years is: "Languages". If you take a look at the proposals you have received (or will) so far: the contraceptive pill, the scientific method (whatever that means), the quantum theory, and so on, they could not have even been thought out, let alone conveyed, without the aid of a language. I do not mean a language in particular, but all the languages, dead or alive. Of course one tends to think that live languages deserve the credit, but without the so-called "dead languages", such as Latin, the live ones simply would not exist. If one accepts that language is the most important invention in the past 2000 years, one has to concede that the "Human Brain" is the most important inventor during the same period.

In my opinion, the printing press comes second to languages as the most important invention in the past 20 centuries; this puts Johann Gutenberg (c.1400-1468) as the second most important inventor of all, since one can easily pinpoint him as the Father of the printed letter. Without a (written) language, specially when it conveys concepts and feelings, all cultures — scientific, literary or otherwise — would be all but a conceptless matter. The Third Culture simply could not breathe.

One can speculate ad nauseam about which language in the current state of world affairs, including the Internet, is the most important one of all. I have some ideas, to theorize about them, though, is beyond your original question.

After reading the various answers to the question, I'm going to sneak through the door opened by Philip Anderson and nominate a discovery instead of an invention. And it is the Copernican Theory. Generally it was a counter-intuitive idea, and it ran opposite to the interpretation of senses (not to mention the Church) I mean, one could "see" the sun going across the sky. What could be more obvious than that? A nice move. It took a lot of intellectual courage, and taught us more than just what it said.

We are using it now. The internet. Of course the internet relies on numerous other inventions (chips, networking, CRTs, telephones, electricity etc). The reason why the internet isn't an obvious choice at first glance (besides the fact that is so present in our lives we can fail to notice it) is that its power has not yet begun to fully manifest itself. We still have schools, offices, the post office, telephone companies, places of entertainment, shopping malls and such, but we won't for long. Information delivery methods affect every aspect of how we live. If we don't have to walk to town to find out what's going on, or to shop, or to learn, or to work, why will we go to town? Schools (which have not been able to change) will completely transform themselves when better course can be built on the internet than could possibly be delivered in a university. Of course, we haven't seen that yet, but when the best physicists in the world combine to deliver a learn by doing simulation that allows students to try things out and discuss what they have done with every important (virtual) physicist who has something to say about what they have done, the only thing universities will have to offer will be football.

Shopping malls aren't gone yet but they will be. Why go to a store to buy music CDs any more? You can listen to samples of whatever you want and click a button for delivery while seated at home. Any object that needn't be felt and perused to be purchased will find no better delivery method than the internet. Newspapers? Not dead yet, but they will be. Pick an aspect of the way we live today and it will change radically in the coming years because of the internet. Life (and human interaction) in fifty years will be so different we will hardly recognize the social structures that will evolve. I don't know if we will be happier, but we will be better informed.

I don't need a page. The answer is clear: inventions are concepts, not just technologies, so the most important are the concepts of democracy, of social justice, and the belief in the possibility of creating a society free from the oppressions of clas, race, and gender.

Good question!

My immediate response (without even thinking) was the contraceptive pill. My mother had six children in five and a half years and it was only the invention of the pill that saved our family from becoming a mini-nation-state in its own right. But since Colin Blakemore has already described so well its immense importance, let me suggest another "invention" — electrification.

Why electrification? For a start, one of my most vivid childhood memories is of my mother seemingly spending endless hours washing nappies and clothes by hand. The electric washing machine and other electric home gadgets (vacuum cleaners, fridges, food processors et cetera) have freed billions of women from the endless drudgery of heavy-duty housework. By bringing us light and heat and power on tap, electricity has truly transformed life — not just in the home, but in almost every industry. Modern manufacturing would be impossible without electricity. Ditto the modern office. The ability to literally transport power is, I think, the most revolutionary technology to come out of modern science. And of course, it is the ability to transport electric power at the micro level that has made possible silicon chips, and the attendant computer and information revolution. Far more than Einstein and Bohr, Faraday and Maxwell are the true "heroes" of the modern technological world.

ELECTRICITY CONTAINS THE WORD CITY — WHICH CERTAINLY IS OUR MOST COMPLEX INVENTION & FROM THE DENSITY OF HUMAN INTERACTION ALL ELSE FLOWS.

The question does most of the answering: "What Is The Most Important Invention In The Past Two Thousand Years?"

That lets out agriculture, writing, mathematics, and money. Too early.

"Most important" would suggest looking for inventions near the beginning of the period, since they would have had the most time for accumulative impact.

Where did that number "Two Thousand" come from? From the approaching Year 2000, which is a Christian Era date — now referred to as "Common Era": 2000 CE. That's quite a clue.

The most important cultural — hence all-embracing — invention is a religion. Only two major religions have been invented in the last two millennia, Christianity and Islam. Try to imagine the last two millennia, or the present, without them.

The Universal Turing Machine. Because it is universal.

Not only as the theoretical archetype for digital computing as we practice it today, but as a least common denominator — translating between sequence in time and pattern in space — that lies at the foundations of mathematics and suggests the possibilities of a communications medium we have only just begun to explore.

Life and intelligence that achieves widespread distribution across the cosmos (and over time) may be expected to assume a digital representation, at least in some phases of the life cycle, to facilitate electromagnetic transmission, cross-platform compatibility, and long-term storage. This requires a local substrate. And we are doing our best, thanks to the proliferation of our current instantiation of the UTM (known as the PC) to help. When we establish contact with such an intelligence, will we receive instructions for building a machine to upload Jodie Foster? Probably not. The download will proceed the other way. To paraphrase Marvin Minsky: "Instead of sending a picture of a cat, there is one area in which they can send the cat itself."

(Well John, you did say most important invention, not the one we should be most proud of). The invention (and detonation) of the atomic bomb has changed the world more profoundly than any other human development in the last 2000 years. In seconds, nearly 200,000 people were dead or dying in Hiroshima, and consciousness was forever changed on our planet. Although the arms race fueled our economy for a few more decades, the bomb set into motion a 'warfare stalemate'. With the ability to destroy our planet within the realm of possibility, we were forced to examine our rules of war, and seek new means of engagement to work out our differences. And although hundreds of wars are going on at any time on our planet, there are checks and balances, underscored by the horror of Hiroshima and Nagasaki.

Please note that if you were to have phrased the question to include time prior to 2000 years ago, then I would have suggested that our most powerful invention would be song.

My personal favourite is the place value notation system combined with the use of a symbol 0 for Zero to denote a nonexistent number marks the birth of modern mathematics. I think this is the greatest invention, but I am being a little jingoistic—it was invented in India in the 4th or 5th century BC, systematised by Aryabhatta in the 4th century AD by the Indian Astronomer and then transmitted to the West via the Arabs. And Maths of course is essential for all science.

Some of your jump-start friends and colleagues seem to have ignored your (arbitrary?) cutoff date, so I will too. I think you'd have to go a long way to find a more important invention than the basket. Without something to gather into, you cannot have a gathering society of any complexity, no home and hearth, no division of labour, no humanity.

This is not an original insight. I ascribe it to Glyn Isaac, a sorely-missed palaeoanthropologist. The basket ranks right up there with hay, the stirrup, printing and what have you.

While we're about it, though, I'd like to take issue with Dan Dennett's choice of the battery. Granted it has enabled all the things he says it has (and I seriously considered nominating the Walkman — a bizarre idea, the tape recorder that doesn't record — as the invention with most impact on our lives) but at what cost? All extant batteries (though not fuel cells) are inherently polluting and wasteful. It takes something like six times more energy to make a Zinc-alkaline battery as the battery can store. I can't help but think that if a small portion of the effort that has gone into inventing "better" batteries had gone into, say, solar panels, our world and culture would be even more different.

Thanks for a stimulating time.

Most important invention: CALCULUS

The world today would be very different if the Greeks and not Newton/Leibniz had invented or "discovered" calculus. The world today might have occurred a millennium or two earlier.

Calculus was the real fruit of the renaissance. It began by taking a fresh look at infinity — at the infinitely small rather than the infinitely large. And it led in one stroke to two great advances: It showed how to model change (the differential equation) and it showed how to find the best or worst solution to a well-defined problem (optimization). The first advance freed math from static descriptions of the world to dynamic descriptions that allowed things to change or evolve in time. This is literally where "rocket science" becomes a science. The second advance had more practical payoff because it showed how to minimize cost or maximize profit. Thomas Jefferson claimed to have used the calculus this way to design a more efficient plow. Someday we may use it to at least partially design our offspring to minimize bad health effects or (God forbid) maximize good behavior.

Calculus lies at the heart of our modern world. Its equations led to the prediction of black holes. We built the first computers to run other calculus equations to predict where bombs would land. The recent evolution of calculus itself to the random version called "stochastic calculus" has led to how we price the mysterious financial "derivatives" contracts that underlie the global economy. Calculus has led us from seeing the world as what Democritus called mere "atoms and void" to seeing the world as atoms that move in a void that moves.