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

The most important invention in the past two thousand years is the printing press. When William Caxton published 'The Canterbury Tales' in the 15th Century with his newly invented printing machine, he dramatically accelerated the separation of human culture from nature, eclipsing the direct experience of natural processes that continues in the oral tradition and replacing it by words on a page. This cut in two directions. (1) The power of nature diminished so that science and technology could start the systematic program of gaining knowledge for control of nature, liberating people from drudgery and freeing the imagination. (2) At the same time, nature was degraded to a set of mechanisms that humans could manipulate for their own purposes, and the 'rape of nature' began in earnest. We are now reaping twin harvests: vastly expanded potential for written communication through the internet, as in this exchange of views at the Edge web site; and a vastly degraded planet that won't support us much longer, as things are going. Can we use one to save us from the other? We can now connect with each other as never before; but what about nature?

John, The most important invention is the Indo-Arab counting system with 0,1,2,3,4,5,6,7,8,9 with its positional information content (so 111 means one hundred plus one ten plus one unit), zero symbol, and operator property that by adding a zero to the righthand end of a string multiplies the number by the base value of 10. This system of counting and enumeration is completely universal and lies at the foundation of all quantitative science, economics, and mathematics.

My nomination for the most important invention of the past 2000 years is probability theory, which was mainly put together in a series of steps between 1654, when Blaise Pascal proposed a solution for splitting the pot in an unfinished game of chance, and 1843, when Antoine Cournot offered a definition of chance as the crossing of two independent streams of events. I don't nominate it simply because probability theory laid the foundation for statistical analysis, which provided us with a vocabulary without which most scientific discoveries made in the last century would have been (literally) unthinkable.

Nor do I nominate probability theory because it gave us for the first time a trustworthy tool for deciding how to apportion belief to multiple sources of evidence. Probability theory had even more fundamental epistemological implications whose importance is under-appreciated in our time because those implications are so seamlessly integrated into the foundations of our modern world view. Until the nineteenth century, the idea that there could exist deep regularities underlain by pure chance — regularities arising from distributions of events which were themselves the result of multifarious unmeasurable causes — was not only almost unknown (Aristotle had hinted at it, as he seems to have hinted at everything), but actually philosophically repugnant. It required the invention of probability theory to make this idea thinkable.

In making it possible to think about such abstract regularities, probability theory rescued us from two philosophical shackles which had held us back from the beginning of history: that of needing to postulate a centralized controller that made everything come out right, and that of assuming that "what you see is what you get" — i.e. that the proper objects of scientific study are roughly identical to the direct objects of the senses. Though perhaps they have still not been totally removed, those philosophical shackles needed to be at least loosened in order for science to get moving.

A whole new world of law-obeying objects to be studied was opened up by probability theory. Neither Darwin's theory of natural selection, nor Maxwell's theory of statistical mechanics (both published in the same year, only 140 years ago) would have been thinkable before probability theory was thinkable. Without probability theory, human kind would be (and was) unable to even conceive of the explanations for many — probably most — of the phenomena which we have ever explained.

Earlier contributors have already staked out the intellectual high road of mental constructs like scientific method and the calculus, so I'll retreat to the most prosaic, literal reading of your question: What is the one device invented by one person at one moment during the past 2,000 years that has had the most influence to date?

I'd be a traitor to my inky profession if I didn't at least echo the nominations for Johann Gutenberg's movable-type printing press. But in the spirit of the game, let me throw support behind something else: Alessandro Volta's electric battery of 1800.

Static electricity was known since at least the time of the Greeks, but study of it had largely stalled. When Pieter van Musschenbroek built and discharged the first Leiden jar in 1745, nearly killing himself in the process, he also jolted the study of electricity back to life. But it was Volta's invention of a steady source of current, inspired by the electrochemical observations of Galvani, that revolutionized technology and physics. Without it, Oersted could not have proved that electricity and magnetism were different faces of the same force, electromagnetism. Electrochemistry itself offered clues to the underlying electrical nature of all matter. And of course, Volta's battery was the forerunner of all the electrical devices that have transformed the world over the past two centuries.

What I find so appealing about Volta's creation is that it had immense practical significance but also opened to us a world of physical phenomena that in themselves changed our understanding of the universe. Yet it was not a bolt-from-the blue inspiration; it pulled together other threads of discoveries by Volta's contemporaries. There's a lesson about greatness in there somewhere.

Text is Special

It seems to me, as it will no doubt to many others, that the printing press has changed the world more than any other invention in the past two millennia. But why has such a simple technology had such a huge influence? And why, after 500 years, has no one invented a superior replacement?

I suspect it is because text has a special relationship to the human mind. Printing is the third wave of the biggest innovation, the one that started with the co-evolution of language, thought and speech. Speech makes it possible to share and compare internal models of the external world, a capacity that gives huge selective advantages. But acoustic vibrations are ephemeral, fading in moments into questions about who said what, when.

Writing, the second wave, is like a blast of super-cooled air that freezes words in mid-flight and smacks them onto a page where they can be examined by anyone, anywhere, anytime. Writing makes possible law, contracts, history, narratives, and poetry, to say nothing of sacred texts with their overwhelming influence. Printing transformed writing into the first mass medium, and the world has never been the same since. In the half-century that followed Gutenberg's 1446 Bible, over a thousand publishers printed over a million books. Suddenly it was worthwhile, and soon essential, for even ordinary people to learn to read. Now, people whose brains have trouble with this trick are at a severe disadvantage, while some with particular verbal felicity can make a living just by arranging words on paper.

Is text merely a temporary expedient, necessitated by the previous inability to record and transmit speech and images? We will soon see. In just a few years, sensors, storage and bandwidth will be so inexpensive that many people will be unconstrained by technical limitations. This affords a fine opportunity to make bold predictions that can be completely and embarrassingly wrong, as wrong as the predictions that said that e-mail would never catch on. In that spirit, I predict that voice and video attachments to e-mail, "v-mail" and "vid-mail," will be the next big thing, and they will create all manner of consternation. At first they will be hailed as more personal and more natural, thanks to the increased content carried by intonation and exclamations. But soon, I predict, the usual human strivings will give rise to problems.

Many people who previously were forgiven as "liking to hear themselves talk" will be revealed as actually wanting to hear others listen to them talk. Some, especially bosses, will send long soliloquies to hundreds of other people in the expectation that they will be listened to in full. The wonderful veil of privacy in which a reader considers a text will be rent. You won't be able to jump around and skip whole paragraphs in v-mail and vid-mail, as you can in e-mail. Time and attention will be revealed as the valuable resources they are. Many people will post electronic notices equivalent to the one a friend has on his answering machine, "Leave a message, but please KEEP IT BRIEF."

To solve this we will, of course, turn to still more technology. V-mail will be transformed automatically into text so we will have a choice of mediums. What will we choose? It will depend. For emotional endearments, and many narratives, v-mail and vid-mail. For simple facts, and subtle ideas, however, I think will we choose text, at least, that is, until our brains are changed by the selective forces unleashed by these technologies.

My initial thought of how to define the importance of an invention was to imagine the impact which would be caused by its absence. But having just sat through yet another viewing of "Its A Wonderful Life," I am inspired to leave contemplation of the contingencies of history to others better suited to the task. And so, I will vote for my "knee-jerk" response: The Telescope.

The invention of the telescope and its subsequent refinement and use by Galileo marked the birth of the modern scientific method and set the stage for a dramatic reassessment of our place in the cosmos. A technological device revealed conclusively that there is so much more to the universe than is available to our unaided senses. And these revelations, in time, have established the unforeseen vastness of our dynamic, expanding universe, shown that our galaxy is but one among countless others, and introduced us to a wealth of exotic astrophysical structures.

I'd say the notion that people can govern themselves, rather than being governed by someone who claims divine right. (I'm wrestling with that one myself right now, on the Internet.)

Given the amount of self-reference in the answers so far, I'm tempted to nominate this very discussion list as the greatest invention of the past two thousand years, and hopefully out-meta all the other contenders.

I think part of the problem here is the fact that inventions by nature are cumulative, and so when asked to pick out the single most important one, you're inevitably faced with a kind of infinite regress: if the automobile is the most important invention, then why not the combustible engine? (And so onŠ) In that spirit — and in the spirit of nominating things you happen to be working on professionally — I'd nominate the ultimate cumulative invention: the city. Or at least the modern city's role as an information storage and retrieval device. Before there were webs and telegraphs making information faster, there were cities bringing information physically closer together, and organizing it in intelligible ways. It's not a stretch to think of the original urban guilds as file directories on the storage device of the collective mind, combining disparate skills and knowledge bases and placing them into the appropriate slots. (Manuel De Landa has a wonderful riff on this in the first section of his new book, A Thousand Years of Nonlinear History.)

But of course, the city isn't an invention proper, at least in the conventional way that we talk about inventions. It's the sum total of multiple inventions, without each of which the modern city as we know it might not exist.

I think what this discussion makes clear is that we need a better definition of "invention"!

Had you asked two years ago I would have nominated the airplane, for it symbolizes the essence of invention by being composed of other inventions: the wheel, the bicycle, a glider, a prop, and a 12 horse power engine. The airplane is important because it diminishes our parochial view, it too changed the manner of warfare (Hey, nice bomber) and one can argue that it was an early form of the space shuttle. But if by important you mean sweeping, the utility of electricity is pivotal to so many things mundane and great, especially the broadcast of information, the A train, the monitors that tell me if my flight is delayed, this modern version of Gutenberg's press, and Les Paul's guitar. Thomas Edison received 389 patents for electric light and power, and Nikola Tesla patented his Apparatus for Transmitting Electrical Energy. Of course humans no more invented electricity than we invented flight, but utility is key. As I write I am preparing to go out for New Year's Eve, and packing a flashlight, just in case an old programming shut down code of 99 introduces us to the Y2K bug a year early. Should such a power failure occur then, the impact of electrical utility will be known.

As a cognitive linguist whose job is to study conceptual systems, both conscious and unconscious, I was struck by what was meant by "invention."

• The most concrete "inventions" proposed have been gadgets, mechanical or biological — the printing press, the computer, the birth control pill.

• A step way from the concrete specific technical innovations are specific technical inventions of a mental character: Gödel's Theorem, Arabic numbers, the nongeocentric universe, the theory of evolution, the theory of computation.

• A step away from those are the general innovations of a mental character in specific domains like science and politics, e.g., the scientific method and democracy. I would like to go a step further and talk about the invention that was causally necessary for all of the above:

• The most basic fully general invention of a mental character is The Idea of an Idea.

THE IDEA OF AN IDEA

It's a bit more than 2,000, more like 2,500 years, at least in the West. It is an 'invention" in the sense that human beings actively and consciously thought it up: to my knowledge, it is not the case that every indigenous culture around the world objectifies the notion of an idea, making it a thing that can be consciously constructed.

What is required for all other human inventions is the notion that one can actively, consciously construct new ideas. We take this for granted, but it is not a "natural" development. Three-year-old children have lots of ideas and even make up new ideas. But they do not have the Idea of an Idea that they can construct anew; they do not naturally arrive at the idea that making up new ideas is something people do. The Idea of an Idea is a cultural creation that children have to learn.

It is only with the Idea of an Idea that we get conscious specific intellectual constructions like democracy, science, the number system, the computer, the birth control pill, and so on. The Idea of an Idea is the generative notion behind the very notion of an invention and is causally necessary for all specific inventions.

The electric motor, in all its guises where electricty produces mechanical motion. The industrial revolution was restricted to places of work and shared production until the relatively small and clean electric motor enabled the adoption of its bounty into the home; for instance, refrigeration, automated cleaning, cooling, better heating, entertainment, mass data storage, home medical care, and more comfortable personal transportation.

True, many of these aspects were present in the home with simpler technologies (e.g., gravity driven water flow, convective air flow), but it was the electric motor which made them pervasive.

The change in our western lifestyle has been profound and has completely changed our expectations of how our bodies should fit with our surroundings.

A question: what will it take for the computer revolution to truly enter our lives in the way that the electric motor has enabled the industrial revolution to do so?

I've been pondering your millennial/bimillennial question, and I'd like to cheat a bit by giving several answers.

I too offer a vote for the oral contraceptive pill. It is revolutionary for two reasons. First, it makes a quantum leap in the effectiveness of technologies for the control of human fertility — which are found in every known culture and likely date back more than a hundred millennia. The pill and subsequent devices have the potential for a revolutionary impact on the lives of women from puberty to menopause everywhere in the world, allowing women to control their own fertility and thus enabling members of half the human species to control their own adult lives.

In addition, these devices have the potential to save the planet Earth from the ongoing disaster of human overpopulation, with its present and future dire consequences globally of mass poverty, pandemics, warfare and violent confrontations over scarce resources, environmental degradation, and wholesale species extinctions.

My next vote for most important technology of the last two thousand years goes to the gun, or more precisely to a series of European inventions of more efficient killing technologies. The ship-mounted cannon, the Spanish trabuco and the British Snider rifle — to mention just a few weapons from recent centuries — in the hands of members of authoritarian societies (whose populations had exceeded the carrying capacities of their homelands given contemporary agricultural technologies), bent on acquiring new territories, propelled across the Atlantic and Pacific Oceans by ships built according to the most advanced maritime technologies of their eras, effected the European conquest of large portions of the planet's landmass, resources, and human populations. The momentous consequences of the European conquest will continue to play themselves out in every sphere of human life around the globe over the next millennium.

My final vote goes to the revolutionary improvements in hydraulic engineering made beginning in the late nineteenth century that have solved what has for millennia been the single greatest problem of urban life: how to bring clean water in and human waste out of a large nucleated settlement. While the Roman waterworks were brilliantly designed (and their epoch crosses the bimillennial cut-off point of this exercise), improvements in sanitation made only a century or so from the present led, in industrial societies like Britain and the United States, to a revolutionary drop in the death rate from infectious diseases transmitted by fecal contamination of drinking water. These advances in hydraulic engineering have extended human life spans even more than the subsequent discovery of antibiotics.

This technology has diffused only slowly around the globe as it encounters barriers created by unequal distributions of wealth and power. Even so, ironically, our resulting increased longevity, and the increases in population fertility that declines in mortality rates confer when they are unchecked by other variables, contribute dramatically to the ongoing crisis of human overpopulation. This makes the wide availability of advanced contraceptive technology, invented two generations later, all the more critical for the survival and well-being of our species and of the entire planet.

The Thermionic Valve by DeForest in 1915 really was the birth of the electronic age. Without this invention most of us would never have been born. Without electronics this planet would not be supporting the massive numbers of people now living in the West. We would not be able to communicate, compute, manufacture and distribute atoms on the scale we now enjoy. There would be no radio, TV, computers, Internet, modern medicine — engineering, international travel of any scale, atomic power and almost everything we currently take for granted. In fact our species and our civilisation would have stalled without this invention.

This Thermionic Valve is very closely followed by the Transistor in 1945 with Bardeen and Shockley creating the foundation for what you are reading this on — the PC.

The great invention of the modern era is the invention of organized science — scientific societies and journals that foster the accumulation and dissemination of knowledge based on evidence rather than on authority or revelation. Before the invention of these organizations the accumulation of scientific knowledge was slow, because there were no established venues for criticism and education — essential social interactions at the heart of science. Now that these organizations (in the developed world) have become very large (necessitating the proliferation of many subdivisions, to allow for personal interactions on a human scale) they facilitate the unprecedented opportunities for collective knowledge and self knowledge that so many of us enjoy.

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.

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.

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.

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.

Another good question! My perhaps eccentric but nonetheless heartfelt nomination is Western classical music, as epitomized in the compositions of Bach, Beethoven, Brahms, and above all Mozart. Music is a free invention of the human spirit, less dependent upon physical or physiological inventions than most other contrivances. Musical compositions in the Western tradition represent an incredible cerebral achievement, one that is not only appreciated but also imitated or elaborated upon wherever it travels. Most inventions — from nuclear energy to antibiotics - can be used for good or ill. Classical music has probably given more pleasure to more individuals, with less negative fallout, than any other human artifact. Finally, while no one can compose like Mozart and few can play like Heifetz or Casals, anyone who works at it can perform in a credible way — and, courtesy of software, even those of us unable to play an instrument or create a score can now add our own fragments to an ever expanding canon.