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

The horse collar as the most important high-tech invention.

Developed around 1000 AD in northern Europe, it allowed the region to be farmed efficiently and so, it could be argued, was responsible for the rise of civilization there. It also gave its possessors great war-making potential — think of knights in armour, for example. 

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.

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.

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.

I read through the list. Some good ones. I think it is interesting that many found it so difficult to stick to the 2000 year cut off. Is it really the case that all the big inventions happened so long ago? This is surely an important and profound statement, if correct.

I have two suggestions, both within the cut-off period. First, the electric light, born about 50 years before Joseph Swan put a patent on the incandescent lamp in 1878, and then Edison in 1879. Having lived in Africa, where one is often forced to read from fire light, electricity is a god send. Moreover, having invented the incandescent lamp, it didn't take too long to come up with the flashlight, another handy device for those of us working in dark jungles. My second suggestion for great inventions is the aspirin, invented, oddly enough in 1853 in France. Clearly, other medicines have been around, many of which serve comparable functions, but what a useful little pill. Among the Maasai in Kenya, headaches are treated with goat feces, a mud compact to the head. I prefer the aspirin personally.

In my view, questions of "importance" cannot be answered without first specifying "criteria of importance," of "important with respect to what."

Thus, I would give the following answer to your question:

"One criterion for "most important" is that which has most profoundly altered patterns of human mating. Changes in mating can affect the subsequent evolutionary course of the entire species, with cascading consequences for virtually every aspect of human life. Although many inventions have altered human mating over the past 2,000 years, television must rank among the most important. Television has changed status and prestige criteria, created instant celebrities, hastened the downfall of leaders, increased the importance of physical appearance, and accelerated the intensity of intrasexual mate competition — all of which have acutely transformed the nature of sexuality and mating and perhaps forever altered the evolutionary course of our species."

The eraser. As well as the delete key, white-out, the Constitutional amendment, and all the other tools that let us go back and fix our mistakes.

Without our ability to go back, erase, and try again, we'd have no scientific model, nor any way to evolve government, culture, or ethics. The eraser is our confessor, our absolver, and our time machine.

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.

Of course, "What is the single most important invention of the past two thousand years?" is one of those questions that does not really have an answer, like "What is the best novel/symphony/movie?

But if I had to make a choice, it would be the Hindu-Arabic number system, which reached essentially its present form in the sixth century.

Without it, Galileo would have been unable to begin the quantificational study of nature that we now call science. Today, there is scarcely any aspect of life that does not depend on our ability to handle numbers efficiently and accurately. True, we now use computers to do much of our number crunching, but without the Hindu-Arabic number system we would not have any computers.

Because of its linguistic structure, the Hindu-Arabic number system allows humans who have an innate linguistic fluency but only a very primitive number sense to use their ability with language in order to handle numbers of virtually any useful magnitude with as much precision as required.

In addition to its use in arithmetic and science, the Hindu-Arabic number system is the only genuinely universal language on Earth, apart perhaps for the Windows operating system, which has achieved the near universal adoption of a conceptually and technologically poor product by the sheer force of market dominance. (By contrast, the Hindu-Arabic number system gained worldwide acceptance because it is far better designed and much more efficient, for human usage, than any other number system.)

Okay, I'll weigh in with the invention of secularism — getting out from under the thumbs of the gods.

From all we can tell from historians and anthropologists, every ancient society worshipped some god or other. Superstition ran rampant. Human beings denied their own freedom and autonomy by praising or blaming the gods for their fates. Not until some bold minds like Ludwig Feuerbach, Karl Marx, Friedrich Nietzsche and Sigmund Freud did it become thinkable, much less fashionable, to preach atheism. These were inventors of a new order, one that allowed human beings to make up our game as we go along, unfettered by superstitions about the will of the gods or fear of their punishment.

For my part I am appalled at how slowly this invention has been accepted. Over 60 percent of Americans still agree (somewhat, mostly, or strongly) that, "The world was literally created in six days, as the Bible says," (confirmed on three successive national probability sample surveys by the Values and Lifestyles Program at SRI International where I was director of research during the 1980s). Islam claims over a billion devotees. And I find it remarkable the number of highly educated, intelligent adults who still embrace a childlike, wish-fulfilling belief in God.

Without kneeling down to positivism, or overestimating what is knowable, or underestimating the mysteries that remain lurking in the individual and social unconscious, let us nevertheless celebrate our liberation from superstition, remain humble before forces that transcend our individual egos, but accept the collective responsibilities of human freedom, and sing, as my GBN partner, Stewart Brand, did in the epigram for the Whole Earth Catalog: "We are as gods so we might as well get good at it."

I agree that Science is the most important human development is the last 2000 years, but it doesn't quite qualify as an invention. I therefore propose the clock as the greatest invention, since it is an instrument that enables Science in both a practice and temperament.

The clock is the embodiment of objectivity. It converted time from a personal experience into a reality independent of perception. It gave us a framework in which the laws of nature could be observed and quantified. The mechanism of the clock gave us a metaphor for self-governed operation of natural law. (The computer, with its mechanistic playing out of predetermined rules, is the direct descendant of the clock.) Once we were able to imagine the solar system as a clockwork automaton, the generalization to other aspects of nature was almost inevitable, and the process of Science began.

Here is my reply to your fiendish question:

How can we possibly pick the most important invention in the past two thousand years? The real biggies — language, fire, agriculture, art — came too soon. In the last two millennia our world has seen so many inventions that it's hard to think of one that stands above all the rest. The printing press? The computer? The A-bomb? After a bit of this, one is tempted to give a smart-aleck reply and back it up with the semblance of earnest reasoning: "Thousand Island dressing!"

But even this is boring. Somehow we have to break out of the box! Well, if inventions are important, surely it's even more important to invent the social structures that will guarantee a steady flow of new inventions. I've heard it said that Edison was the first to turn invention into a business. Every day he would walk into his lab and say "Okay, what can we invent today?" But the groundwork was laid earlier. Perhaps the invention of a patent office was the key step? Or further back, Bacon's "New Atlantis", which envisioned the techno-paradise we are now all so busy trying to build?

Why hasn't anyone mentioned television??!! Is it too obvious? I think it's the single most powerful and manipulative tool ever invented. It's today's most important source of information and serves as a tremendous behavior patterning device. Since it's inception, crime has risen, sex has increased and the attendance at live performances has died.

My first association for the most (whatever that means) important invention was the unconscious mind, because, I thought to myself, the concept offers some explanation — and thus hopefully later remedies — for the behaviors coming from the darker sides of our nature.

Armed with better understanding of the origins of such behavior, hopefully we could fashion ways out of the irrational clamp that fundamentalist religion, blind nationalism or deep ideology often puts on our conscious awareness. But, one thought later was that I believe the unconscious does indeed exist, so logically it is a discovery, not an invention.

That (somewhat uneasily) suggests psychotherapy (again, whatever that means given all its incarnations — psychotherapy being but one of a basket of techniques to make the unconscious more conscious) as my invention. At least in principle — and often in practice too I believe — it does offer us the opportunity to become more conscious, therefore less inclined to absolute thinking and the subjugation and/or violence absolutism often engenders in the minds of those who don't harbor doubts.

In discussing the causes and possible solutions to global environmental problems (e.g., global warming in particular), I note in dialogues with junior high school students — right on down to senate committees — that we can't easily fix problems we can't see. Thus, solutions to long-term, global-scale systems threats require — in a democracy at least — overcoming any collective denial that our "puny" individual impacts can cause a major disruption at a planetary scale or over timeframes longer than our lifetime.

Admittedly, I'm not going to seriously claim psychoanalysis is as "important" an invention as the scientific method over the past 2000 years (as I recall one of your respondents proposed). What I see as a key invention for the year 2000+, though, is an expanded systems analysis that includes methods to build in an understanding of the role of the unconscious of individuals which leads to lifestyles and behaviors which "scale up" to create unanticipated collective consequences.

Although not directly responsive to your question, the invention I really like — think we will really need — is a fusion of systems analysis with psychotherapy. But the new field of "systems therapy" is yet to be invented!, leaving me dangling uneasily between systems — and psycho-analysis. Perhaps, if armed with insights from tools that integrated physical, biological, social and psychological drivers of our behaviors across a range of scales, rather than always chugging merrily along in business as usual mode, we'd be more aware of the range of consequences of our unconsciousness. Then, if we continued to damage the collective or put the future at risk, at least that would be more of a choice and less of a surprise. With best wishes to all for the holiday season.

Thanks for the reminder. Here's my shot. Perhaps the most challengingly important inventions are those that open up new moral dilemmas, and thus make some people question whether the invention should have been allowed (or precursor discovery sought) in the first place. This even applies to Howard Gardner's suggestion of classical music: I would add Adorno's (I think) statement that, in contrast to some composers, it is impossible to find evil that could have been reinforced by any note written by Mozart. On the other hand, I believe Wagner is still banned in Israel.

But my own suggestion is closer to my professional interests. As delightfully examined in Jared Diamond's Guns, Germs and Steel, writing was at least one of the most important inventions of all time, but Sumerian cuneiform is too old for me to offer it, by 3000 years. So, in agreement with Philip Anderson's nudge, the printing press is my response to the question. After all, even the World Wide Web is just a printing press with electronic and photonic elaborations. But I can't resist looking forward at an editorial fantasy, ignoring all sober estimations of the difficulties involved: a cumulative invention which, if fulfilled, would certainly have a capacity for good and evil. To quote William Gibson's Neuromancer:

".. and still he dreamed of cyberspace...still he'd see the matrix in his sleep, bright lattices of logic unfolding across the colorless void..."

No keyboard, mouse or screen, just neural connections and a many-dimensional space of, at least, information, to explore, organise and communicate at will — perhaps, dare I presumptuously suggest, with occasional help from an editor. I fear it's too much for me to expect, but my grandchildren could love it.

Building autonomous tools is my candidate for the most important invention.

Artificial complex adaptive systems, from robots to any type of autonomous agent, will change our world view in a qualitative way, comparable to the change brought by the use of thing-like tools.

Tinkering with tools has shaped our view of the world and of ourselves. For example, the invention of the pump enabled us to understand the mechanical role of the heart. Science was born when laboratory apparatus was used to select among mathematical theories of the physical world which one correspond most closely to reality. But all those tools have been lifeless and soulless things, and it is no wonder that our scientific world view has tended to objectify everything. Grasping the proper role of the subject pole of experience, through the invention of subject-like tools, may provide the key to a far wider world view.

With the invention of perspective, in the late Middle Ages, we shifted our collective Western experience one-sidedly into the object pole, leaving the subject pole out of the picture. We started looking at the world from behind a window, and a couple centuries later, in science, we attempted to take a God's eye view of the world. By now, we are coming around full-circle, with our science and technology providing us the means of exploration of the role of the subject.

We have only set the first steps towards building artificial subjects. Just as our current artificial objects are vastly more complex than the first wheel or bow and arrow, our artificial subjects will grow more complex, powerful, and interesting over the centuries. But already we can see a glimmer of what lies ahead: our first attempts to build autonomous agents has taught us new concepts. As a result, we are now beginning to explore self-organizing ecological, economic, or social systems; areas of study where thing-like metaphors hopelessly fail.

My suggestion for the most important invention of the last two millennia is the computer because of the way it extends the capacities of the human mind for accurately performing large numbers of calculations and for keeping track of and accessing vast bodies of data. As with any great invention, these enhanced abilities have a light and a dark side. As a scientist I am now able to answer questions that could not be answered prior to the computer. On the dark side is the loss of privacy and the enhanced potential for social control made possible by the ability to manipulate large databases of personal information.

As another candidate, my mother has said that her all time favorite invention is the telephone because of how it allows her to stay in intimate and immediate contact with distant friends.

My immediate reaction to the question was to choose between the printing press and any of a set of public health-related inventions (antibiotics, sewage treatment, ...). And since it seems as though we might never have had the public health advances without the printing press, but did, in fact, have the printing press without the public health advances, I'd have to choose the printing press.

Why? Because it opened the possibility that knowledge (information, wisdom) could be disseminated beyond a small number of privileged individuals, thus permitting larger numbers to share or debate world-views and to build upon past and present ideas. Thus far, at least, new electronic technologies (radio, movies, television, computers) have been employed as extensions of this broadening of access to knowledge, altering the medium of exchange but not the concept. At some time in the future they may lead to more fundamental changes in the human condition, but not yet, I'm afraid.

If you read through this growing list, you will see that people tend to discover that the most important invention in the last 2000 years is something they just happen to know a lot about. Well, I know a lot about some important inventions — like the codex book (and the consequent idea that a book can be a manual for living — that leads us to the 19th century and its dead ends) and like the computer (which gives us a model for ignoring the manual and just living by experiment), but I think it is quite undeniable that there is something far more important going on: effectual health care. Not just antibiotics, not just birth control, not just anesthesia (to say things mentioned here), but the underlying fundamental fact that we have learned to cross the scientific method with care for human beings and save lives. A thought experiment I like to have people play is this: review your own life and imagine what it would have been like without late 20th century health care. Would you still be alive today? An astonishingly large number of people get serious looks on their faces and admit they wouldn't: I wouldn't, that's for sure. It's medical techniques, it's antibiotics, but it's also vitamin pills and — in some ways most wondrously cost-effective of all — soap, as in the soap doctors use to wash their hands.

Quite a good question and some very interesting responses. However, I take a more pragmatic view. For me, the steam engine was the most important invention in the past two thousand years. The steam engine freed man and beast from physical labor. No other invention had so many different and versatile uses. Man could cut down entire forests to feed sawmills to build cities, quarry stone, propel trains and ships to make the world a smaller place, power factories, and generate electricity. Agrarian society was over and industrialism reigned. Most importantly, the steam engine created more leisure time for mankind. No longer was leisure a pastime for the idle rich. The pursuit of leisure and the changes it created in society far outstripped the first 18 centuries. Without the steam engine, our society would be radically different from today.

Others in this science-minded group have appropriately mentioned the scientific method. Speaking for my discipline let me sharpen this: When it comes to thinking smart — to sifting reality from wishful thinking — one of the great all-time inventions is the control group. If we want to evaluate medical claims (from bloodletting to new drugs to touch therapy), to assess social programs, or to isolate influences on human behavior we construct a controlled reality. By random assignment we form people into equivalent groups which either receive some experience or not — thereby isolating the factor of interest. The power of the controlled experiment has meant the death of many wild and wacky claims, but also the flourishing of critical thinking and rationality.

Joe Traub already nabbed the invention I would have chosen; empirical method. So I'll stake out a different claim. For present purposes, I'll claim that the most significant invention of the last 2000 years was the human ego.

The ego I'm talking about is the self-concerned human that Harold Bloom credits Shakespeare with having invented. It's the thing that William Manchester finds definitively missing in the Medieval mind. Jostein Gaarder, in his children's philosophy novel, Sophie's World, blames St. Augustine for inventing it. It's what the fuss is about in Nietzsche. It's what exists in existentialism.

In truth, I'm not entirely convinced that I don't find good evidence of this creature in pre-Christian/Common-era texts. (Thomas Cahill thinks it was a gift from the Jews.) But it does seem that the sense of individual self, outfitted with moral responsibility, free will, consciousness, and — most importantly — neurotic self-obsession, at one time did not exist, and then did.

That same sense of self is now being challenged by AI-ish members of the EDGE community. Perhaps it will disappear, just as it once appeared. So it is reasonable to think of the ego as a natural inhabitant of approximately the last 2000 years.

One could argue that the ego had to precede empirical method. The shift from pure rationality to empiricism relied on an acknowledgement of differing perspectives of observation (while pure rationality was thought to be independent of personal perspective). So the self was needed in order to have a starting point from which to pose theories and to make measurements in order to test them. Only an ego can have imperfect enough knowledge to make mere guesses about what's going on in the universe, and the hubris to test and improve those guesses.

I personally hope the ego survives the computer.

The battery, the first major portable energy packet in the last few billion years. When simple prokaryotes acquired mitochondria several billion years ago, these amazingly efficient portable energy devices opened up Design Space to multicellular life of dazzling variety. Many metazoa developed complex nervous systems, which gave the planet eyes and ears for the first time, expanding the epistemic horizons of life by many orders of magnitude. The modest battery (and its sophisticated fuel cell descendants), by providing energy for autonomous, free-ranging, unplugged artifacts of dazzling variety, is already beginning to provide a similarly revolutionary cascade of developments. Politically, the transistor radio and cell phone are proving to be the most potent weapons against totalitarianism ever invented, since they destroy all hope of centralized control of information. By giving every individual autonomous prosthetic extensions of their senses (think of how camcorders are revolutionizing scientific data-gathering possibilities, for instance), batteries enable fundamental improvements in the epistemological architecture of our species. The explosion of science and technology that may eventually permit us to colonize space (or save our planet from a fatal collision) depends on our ability to store and extract electrical power ubiquitously. Our batteries are still no match for the mitochondrial ATP system — a healthy person with a backpack can climb over mountains for a week without refueling, something no robot could come close to doing — but they open up a new and different cornucopia of competences.

This is a good question. My suggestion is not original. I don't remember who gave me the idea, but it was probably Lynn White, with Murray Gell-Mann as intermediary.

The most important invention of the last two thousand years was hay. In the classical world of Greece and Rome and in all earlier times, there was no hay. Civilization could exist only in warm climates where horses could stay alive through the winter by grazing. Without grass in winter you could not have horses, and without horses you could not have urban civilization. Some time during the so-called dark ages, some unknown genius invented hay, forests were turned into meadows, hay was reaped and stored, and civilization moved north over the Alps. So hay gave birth to Vienna and Paris and London and Berlin, and later to Moscow and New York.

Computers, not for current reasons but because they're essential to prevent a collapse of civilization in the future. Computers may allow us to understand the earth's fickle climate and how it is affected by detours of the great ocean currents. These detours cause abrupt coolings within a decade that last for centuries, sure to set off massive warfare as the population downsizes to match the crop failures. "Natural" though these worldwide coolings have been in the past, with their forest fires and population crashes, they're not any more inevitable than local floods — if we learn enough about the nonlinear mechanisms in order to stabilize climate. Computer simulations are the key to a "preventative medicine" of climate, what may allow human scientific ingenuity to keep civilization from unraveling in another episode of cool, crash, and burn.

My choice for the most important invention? The contraceptive pill.

Why? Well, there are, of course, the well-rehearsed answers to that question. The pill did indeed fertilize the sexual liberation of the sixties, did stimulate feminism and the consequent erosion of conventional family structure in Western society — perhaps the most significant modification in human behaviour since the invention of shamanism. It did help to change our concept of the division of labour, to foster the beginnings of an utterly different attitude to the social role of women. But, arguably the important sequel of the pill is the growing conception that our bodies are servants of our minds, rather than vice versa. This relatively low-tech invention has triggered a cultural and cognitive revolution in our self-perception. It has contributed to our ability to accept organ transplantation, the notion of machine intelligence, gene therapy and even, eventually, germ-line genetic manipulation. It has shifted the quest of human beings from controlling their physical environment to controlling themselves — their own bodies and hence their physical destinies.

As usual you are a font of important, stimulating ideas and have gathered together an awesome collection of minds for your latest survey. Here is my response.

In 105 AD, Ts'ai Lun reported the invention of paper to the Chinese Emperor. Ts'ai Lun was an official to the Chinese Imperial court, and I consider his early form of paper to be humanity's most important invention and progenitor of the Internet. Although recent archaeological evidence places the actual invention of papermaking 200 years earlier, Ts'ai Lun played an important role in developing a material that revolutionized his country. From China, papermaking moved to Korea and Japan. Chinese papermakers also spread their handiwork into Central Asia and Persia, from which traders introduced paper to India. This is why Ts'ai Lun is one of the most influential people in history.

Today's Internet evolved from the tiny seed planted by Ts'ai Lun. Both paper and the Internet break the barriers of time and distance, and permit unprecedented growth and opportunity. In the next decade, communities formed by ideas will be as strong as those formed by geography. The Internet will dissolve away nations as we know them today. Humanity becomes a single hive mind, with a group intelligence, as geography becomes putty in the hands of the Internet sculptor.

Chaos theory teaches us that even our smallest actions have amplified effects. Now more than ever before this is apparent. Whenever I am lonely at night, I look at a large map depicting 61,000 Internet routers spread throughout the world. I imagine sending out a spark, an idea, and a colleague from another country echoing that idea to his colleges, over and over again, until the electronic chatter resembles the chanting of monks. I agree with author Jane Roberts who once wrote, "You are so part of the world that your slightest action contributes to its reality. Your breath changes the atmosphere. Your encounters with others alter the fabrics of their lives, and the lives of those who come in contact with them."

There is an inherent bias in all such surveys, because everyone strives to be original and surprising and so shuns the obvious but probably more correct answers — such as steel, or moveable type, or antibiotics, to name but three obvious things that have utterly transformed not only how people live but the way theyexperience life.

The only way I can think of being surprising is to violate John's terms and go back 6,000 years. But if I will be permitted to do so, I would argue that the single invention that has changed human life more than any other is the horse — by which I mean the domestication of the horse as a mount. The horse was well on its way to extinction when it was domesticated on the steppes of Ukraine 6,000 years ago, but from the moment it entered the company of man the horse repopulated Europe with a swiftness that announced the arrival of a new tempo of life and cultural change. Trade over thousands of miles suddenly sprang up, communication with a rapidity never before experienced became routine, exploration of once forbidding zones became possible, and warfare achieved a violence and degree of surprise that spurred the establishment and growth of fortified permanent settlements, the seeds of the great cities of Europe and Asia. For want of the horse, civilization would have been lost.

My nomination is the invention of the scientific method.

The Greeks believed we could understand the world rationally. But the scientific method requires that we ask questions of nature by experimentation. This has led to the science and technology that has transformed the world.

I always liked Lynn White's story about how the stirrup revolutionized warfare and made feudal society and culture possible. Or Lefebre des Noettes' argument about how the invention of the rudder made extensive sailing and the consequent expansion of Europe and its colonization of the world possible. But it's sobering to realize that it took us over one thousand years to realize the impact of these artifacts. So I am not at all sure we have at this time a good grip on what the most important inventions of the past millennia have been. Certainly the contraceptive pill is a good candidate, and so is the scientific method. I am also intrigued by the effects of such inventions as the flag — a symbol of belonging that millions will follow to ruin or victory independently of biological connectedness; or the social security cardthat signifies that we are not alone and our welfare is a joint problem for the community; or the invention ofcivil rights which however abused and misused is pointing us towards a notion of universal human dignity that might yet eclipse in importance all the technological marvels of the millennium.

In his work on the foundations of chemistry, it occurred to Antoine Lavoisier (and also, I suppose to Joseph Priestly) that the smell of a chemical was not necessarily a 'property' of that chemical, but a property of some related chemical that had the form of a gas, which therefore could reach the nose of the observer. Thus solid sulfur itself has no smell, but its gaseous relatives, sulfur dioxide and hydrogen sulfide have plenty of it. Perhaps this tiny insight was the key to the transformation of chemistry from a formerly incoherent field into the great science of the 19th and 20th centuries.

The question is impossible to answer with one thing; one could for instance say with some justification "the germ theory of disease" but then that goes back to the microscope — otherwise no one would ever have seen a germ — and that to the lens, and eyeglasses may be as important as germs, ft as germs, and so on. But I will give you my entry; to the amazement of my colleagues who think of me as the ultimate antireductionist, I will suggest a very reductionist idea: the quantum theory, and I include emphatically quantum field theory. The quantum theory forces a revision of our mode of thinking which is far more profound than Newtonian mechanics or the Copernican revolution or relativity. In a sense it absolutely forces us not to be reductionist if we are to keep our sanity, since it tells us that we are made up of anonymous identical quanta of various quantum fields, so that only the whole has any identity or integrity. Yet it also tells us that we really completely know the rules of the game which all these particles and quanta are playing, so that if we are clever enough we can understand everything about ourselves and our world. Note that I said understand, not predict — the latter is really in principle impossible, for reasons which have little to do with the famous Uncertainty Principle and a lot to do with exponential explosions of computations.

I would agree with whoever said "the scientific method" if I thought that was a single thing invented at some identifiable time, but I know too much history and see too much difference between different sociologies of fields.

Why has no one mentioned the printing press yet?

The other really profound discovery is the molecular basis of evolution, for which probably Oswald Avery deserves more credit than anyone. Evolution itself has, like the scientific method, much too complicated a history to class as a single invention.

The most important invention of all time was the interrogative sentence. i.e., the asking of questions.

However, the original request was for the most important invention of the last 2,000 years, not of all time. To that I would say, space travel.

Of course, it may be centuries before we know the full consequences of space travel.