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

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

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

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.

Founder and director of Psi-Phi Communications

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

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

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

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

science editor of Weidenfeld & Nicholson

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.

Professor of Biology at Schumacher College

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?

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?

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.

Founding Partner, Formicio; Chairman & CEO, Cochrane Associates

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.

Physicist, Perimeter Institute; Author, Einstein's Unfinished Revolution

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.

Professor of Neurobiology and Psychiatry, UCSF; Author, Making Sense of People

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.

Professor of Biology, Amherst College; Author, Plague Time

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.

Post doctoral fellow in the Department Of Psychology, University Of Alberta

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.

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.

Editor-In-Chief, Scientific American

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.

Professor Emeritus of Chemistry and Senior Research Scientist, New York University; Author, Planetary Dreams

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?

Research Professor of Life Sciences, Director (2014-2019), Center for Evolution and Medicine, Arizona State University; Author, Good Reasons for Bad Feelings

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.

Columnist; Broadcaster in areas of technology and computing

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.

Co-founder of the World Science Festival and Chairman, Science Festival Foundation; Professor of Mathematics & Physics, Columbia University; author, The Hidden Reality, The Fabric of the Cosmos, and The Elegant Universe

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.

Retired Director of the American Institute of Physics

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.

Investor; Chairman, EDventure Holdings; Executive Founder, Wellville; Author: Release 2.0

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.)

Physicist

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.

Editor-In-Chief and co-founder of Feed

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"!

Communications Expert; Author, Smart Mobs

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.

Paleontologist; Author, Hominid Gang

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.

Author; The Cancer Chronicles, The Ten Most Beautiful Experiments; Columnist, The New York Times

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.

Fellow at The Rockridge Institute; Author, The Little Blue Book

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.

Professor of Neural Science, Psychology, Psychiatry, and Child and Adolescent Psychiatry, NYU; Director Emotional Brain Institute; Author, Anxious

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.

Panasonic Professor of Robotics (emeritus); Former Director, MIT Computer Science and Artificial Intelligence Lab (1997-2007); Founder, CTO, Robust.AI; Author, Flesh and Machines

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?

Professor Emeritus, University of Maryland, Baltimore County; Author, Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond

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.

Professor, Department of Anthropology, University of Wisconsin

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.

Mills Professor of Philosophy of Mind at the University of California

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.

Director emeritus of Fermi National Accelerator Laboratory

If we suggest anything other than the Printing Press, Brockman will cancel our Christmas bonuses and New Years Eve turkey. So: the greatest invention in the past two thousand years is the printing press. Next is the thermos bottle.

Social and Cognitive Scientist; CEU Budapest and CNRS Paris; Co-author (with Deirdre Wilson), Meaning and Relevance; and (with Hugo Mercier), The Enigma of Reason

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

I 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.

Director of JavaSoft's Corporate and ISV Relations for Sun Microsystems, Inc

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

Professor of Psychology, University of Texas, Austin; Author, When Men Behave Badly

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

"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."

Writer; Speaker; Thinker, Copenhagen, Denmark

THE MIRROR

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

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

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

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

Media Analyst; Documentary Writer; Author, Throwing Rocks at the Google Bus

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.

Theoretical physicist; Author, The Janus Point

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

Director of The Human Origins Program

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.

Contributing Editor at Reason

The most important invention in the last 2000 years has to be the moveable-type printing press. Cheap book production put the printed language in the hands of the masses and led directly to the rise of literacy. Once you have a large literate class, you see the democratic impulse flourish — even a moderately educated populace begins to make judgments about its rulers and its mode of government. Cheap book production also advances both scientific and historical knowledge by ensuring that valuable source documents are duplicated and preserved and (just as important, really) ensuring that those old documents are readable. Cheap book duplication makes it possible to quickly build a cadre of scientists and historians who've read the same works and thus share a common body of knowledge. Finally, moveable type makes it possible for the past to speak to the future en masse in a way that the evanescent oral tradition never could.

It's helpful to look at the other inventions listed as the most important in the last 2000 years and try to imagine how they might have come about had there been no moveable-type printing press.

Professor of psychology and a professor of computer science and engineering at the University of Michigan at Ann Arbor

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.

Theoretical Physicist; Foundation Professor, School of Earth and Space Exploration and Physics Department, ASU; Author, The Greatest Story Ever Told . . . So Far

If I take the word "important" to suggest an invention that will have "the greatest impact on the next 2000 years" (after all, it is the future that counts, not the pa st!),then the invention of the programmable computer seems to me to be the most important invention of the last 2000 years. ( I am not including in my list of possibilities here ideas and concepts, since I don't think they qualify as inventions, and I suspect that the intent of the question is to explore technology, not ideas...). While the printing press certainly revolutionized the world in its time, computers will govern everything we do in the next 20 centuries. The development of artificial intelligence will be profound, quantum computers may actually be built, and I am sympathetic to the idea I first heard expressed by my friend Frank Wilczek, that computers are the next phase of human evolution. Once self-aware, self-programmable computers become a reality, then I have a hard time seeing how humans can keep up without in some way integrating them into their own development. The only other invention that may come close is perhaps DNA sequencing, since it will undoubtedly lead to a new understanding and control of genetic and biology in a way which will alter what we mean by life.

research astronomer at the Joule Physics Laboratory at the University of Salford

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.

Film director and writer-producer

Richard Gatling started with a cotton seed sowing machine and graduated to a weapon that rotated 10 barrels of 0.45 in bullets at a rate of 1000 rounds a minute. The Confederacy didn't purchase the thing 'til after the Civil War. But in the next several decades it was bought and used by powerful armies around the globe. Finally it proved its battle merit in Africa where it mowed down thousands of unsuspecting Zulus. The Gatling Gun was the first weapon of mass destruction. Moreover, it spawned the ongoing, if clumsy, debate about weapons being banned for the sake of mankind.

Professor of Computer Science at Stanford University

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.

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

It all depends on how you define important, of course. But to my mind the most important invention is telecommunications technology: the telegraph, the telephone, and now things like the Internet. Until about 150 years ago, it was impossible to communicate with someone in real time unless they were in the same room. The only options were to send a message (or go in person) by horse or ship.

The early optical telegraphs of the 1790s made long-distance communication possible at hitherto impossible speeds, at least for the governments that built them, but they were not available for general use. Then in the 1840s, the electric telegraph enabled people to send messages over great distances very quickly. This was a step change, though its social consequences took a while to percolate. At first, telegraph operators became the pioneers of a new frontier: they could gather in what we would today call chat rooms, play games over the wires, and so on. (There were several telegraphic romances and weddings.) The general public, of course, was still excluded, and had no direct access to the real-time nature of the technology. But the invention of the telephone in the 1870s made real-time telecommunications far more widely available.

Today, in the developed world at least, we think nothing of talking with people on the other side of the world. During the course of a normal working day, many people spend more time dealing with people remotely than they do face-to-face. The ubiquity of telecommunications technology has become deeply embedded in our culture. Of course, life has sped up as a result. But we watch TV and use telephones, fax machines and, increasingly, the Internet, almost unthinkingly. If the mark of an advanced technology is that it is indistinguishable from magic, then the mark of an important one is that it becomes invisible — that we fail to notice when we are using it. That makes the significance of telecommunications technology very easy to overlook, and underestimate.

professor of mathematics at Temple University

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.)

Producer; Founder, Managing Director, Skyscraper Productions; Author, The Antisemitism Wars: How the British Media Failed Their Public

Clearly, none of us is playing by the rules in this game, otherwise we would all concentrate on a few key inventions that are obviously the most important — the Indo-Arabic number system including zero, computers, the contraceptive pill. Instead we are all reading the suggestions so far and then trying to select something different. Because I've come in late my friend Nicholas Humphrey has bagged my first thought — reading glasses, so I'll break the rules in two ways by choosing something which was invented more than two thousand years ago but refined over the last two thousand years.

In fact I'll break the rules a third time by choosing two things — chairs and stairs. Apart from the fact that they rhyme, they also represent an imaginative leap by seeing the value to the human anatomy of an idealised platform in space at a certain height. A platform of, say, 7 inches would enable a person to raise himself towards some higher objective without undue effort, but that's as far as it goes.

But if, from that new starting point, a further platform of the same height could be constructed, the objective could be more closely approached. The refinements have all been to do with the fact that the greater the height you want to reach the larger the floor area that has to be taken up by the staircase. But landings and 180 degree turns helped to solve that problem, along with the even later improvement of a spiral structure.

The consequences of stairs have obviously included greater density of occupation of site areas, but they have also included the propagation of the Muslim religion by allowing muezzins to call the faithful to prayer from minarets. As far as chairs are concerned, the same thought process was involved — seeing the value of a platform at just above knee height and then constructing it.

Portability came in at some stage as well so that instead of finding somewhere — a wall, a rock, etc — of the right height you carry around with you, or position where you liked, the place to park your butt. Somehow, the height was chosen, or evolved, so that we can stay for the maximum time in a fixed position with eyes,hands and arms free to do what eyes, hands and arms are good at. Lying down, standing up, and squatting all get uncomfortable after a while, particularly for reading or writing (although we have to accept that medieval monks seemed to manage O.K, transcribing manuscripts standing up.)

Professor of Cognitive Philosophy, Department of Philosophy and Department of Informatics, University of Sussex, Brighton, UK; Author, Surfing Uncertainty: Prediction, Action, and the Embodied Mind

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.

1923-2016; Emeritus Professor, Formerly, Philosophy Department. University of Calgary, Alberta Canada

My first reaction to your question was The Zero, the next Infinity, but my answer is The Infinitesimal Calculus.

Creating a bridge between the two archetypal fictions 0 and * it makes sense of them. It has become a tool in just about every branch of engineering and science. It provides a language for the formulation of laws and a method for constructing explanations, solutions and predictions. It is alive: its invention in the 17th century — by Leibniz and Newton independently — articulated a concept that had long been vaguely anticipated and applied implicitly, its development is still in progress, leading to the resolution of old puzzles (e.g., Zeno's Paradox) while raising new ones (e.g., the continuum hypothesis). Leibniz had been agonizing over what he called "the labyrinth of the continuum" but the 19th century put the infinitesimal calculus on a firm basis by analyzing the concepts of a limit and of infinity from a variety of view points. Nowadays we are blessed with new developments coming from the quarter of symbolic logic that arose out of a digital (0,1) modeling of rational arguing: non standard analysis vindicates Leibniz' use of "infinitely small" non-zero quantities.

Psychologist, Boston College; Author, How Art Works: A Psychological Exploration

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).

Neuroscientist; Collège de France, Paris; Author, How We Learn

In my opinion, the most important human invention is not an artefact, such as the pill or the electric shaver. It's an idea, the very idea that made all these technical successes possible: the concept of education.

Our brain is nothing but a collection of networks of neurons and synapses that have been shaped by evolution to solve specific problems. Yet through education and culture, we have found ways to "recycle" those networks for other uses. With the invention of reading and writing, we recycle our visual system to do word reading. With the invention of mathematics, we apply our innate networks for number, space, and time to all sorts of problems beyond their original domain of relevance. Education is the key invention that enables all these rewirings to take place at a time when our brains are still optimally modifiable.

As David Premack likes to remind us, homo sapiens is the only primate that has invented an active pedagogy. Without education, it would only take one generation for all the inventions that other have mentioned to vanish from the surface of the earth.

Geochronologist Emeritus, University of California, Berkeley

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!

Editor (Emeritus), Nature; Royal Commissions on environmental pollution and genetic manipulation

I'm amazed that fellow beneficiaries of this site are making such heavy weather of your pre-millennial assignment. Incidentally, surely some have bent your rules in that assorted Sumarians, Assyrians and Egyptians, not to mention Chinese, Greeks and Romans, were well into the recording of history long before 2,000 years ago.

Ab-reacting a little, I was tempted to enter the central locking-systems on modern motorcars (a.k.a. "automobiles") as the greatest contribution to the convenience of modern life, but that's a trivial invention (and should have been incorporated on the model-T).

In any case, there's no doubt in my mind that the invention of the differential calculus by Newton and, independently, by Leibnitz, was the outstanding invention of the past 2,000 years. The calculus made the whole of modern science what it is. Moreover, this was not a trivial invention. Newton know that velocity is the rate of change (with time) of distance (from Galileo, for example) and that acceleration is the rate of change of velocity (with time), but it was far from self-evident that these quantities could be inferred from the geometrical shapes of Kepler's orbits of the planets. Nowadays, of course, mere schoolboys (and girls) can play Newton's game — it's just a matter of "changing the variables", as they say.

In the seventeenth century, it was far from obvious that the differential calculus would turn out to be as influential as later events have shown. Indeed, Daniel Bernoulli claimed (in 1672) that Newton had deliberately hidden his "method of fluxions" in obscure language so as to keep the secret to himself. But Leibnitz's technique was hardly transparent; it fell to Bernoulli himself to interpret the scheme, much as Freeman Dyson made Feynman's electrodynamics intelligible in the 1940s.

Both Newton and Leibnitz appreciated that the inverse of differentiation leads to a way of calculating the "area under a curve" (on which Newton had earlier spent a great deal of energy), but it was Liebnitz who invented the integral sign now scattered through the mathematical literature. That these developments transformed mathematics hardly needs assertion.

But the effect of the calculus on physics, and eventually on the rest of science, was even more profound. Where would be field theories of any kind (from Maxwell and Einstein to Schrodinger/Feynman/Schwinger/Weinberg and the like) without the calculus?

One can, of course, say much the same about the invention of arithmetic, but that long predates 2,000 years ago. The calculus was the next big leap forward.

Professor of Anthropology, University of Michigan; Adjunct Associate Research Scientist, Museum of Anthropology

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.

Managing director of science communications

The tricky part of the question is not what the most important invention is, but the qualifier "in the past two thousand years". Technological innovations alter the frontier between humans and their natural habitat. Because of the insuperable importance of the environment, humans have always sought to maximize the advantage they can take from the laws provided by nature. As a consequence, truly fundamental innovations date back many thousand years ago. The most outstanding innovation of all times was probably the domestication of animals, followed by that of plants. Life in permanent homes, villages and cities, the wheel, the sailing ship, engineering, script, as well as conceptual achievements such as nations, democracy, religion, music and songs, even taxes, interest and inflation all date back way before the beginning of the common era. Several innovations suggested in this forum were actually part of every day routines of Bronze Age people, including, for instance, language, steel, paper, and reading glasses. Scientific method must have also existed in some form, since 14th century BC hydraulic installations in Greece perfectly meet the parameters of the given environment. Even moveable type was known by 1500 BC, as the example of the Discos of Phaistos from Minoan Crete shows. Finally, heliocentricity was first discovered by the astronomer Aristarchos of Samos during the 3rd century BC — but the concept failed peer reviews and its acceptance was thus delayed by 1800 years. Since the principle factors controlling people's lives today already existed 2000 years ago, the skeptic in me would intuitively vote for:nothing worth mentioning.

If we take a stroll through a Roman town 2000 years ago — and ancient Pompeii provides a good example of a city frozen in a moment of every day life — we would find a city containing factories (including one for fish sauce), public baths, athletic stadiums, theaters, plastered roads, proper sidewalks, pubs and, inevitably, brothels — facilities for people who were, for the most part, in better physical shape than us. What distinguishes a modern city from its Roman predecessor? Two things come to mind, the first belonging to the category of conceptual realization:Christianity. The Roman dominion over the western world lasted for about 1000 years — and we might indeed still live in the Roman era, if there would not have been a common denominator which united the many tribes suppressed by the imperious control. This unifying factor was Christianity. — The second prominent innovation which distinguishes a Roman from a modern city is electricity. Only through the invention of electricity is it possible to operate laundry machines and subnotebook computers; two inventions I personally cherish the most, as well as many of the other items suggested in this forum.

However, I recall enjoying a particularly Romantic evening in the usually overcrowded, noisy Cretan tourist resort of Elounda. Some time passed before I realized what made this evening so special — a general power shut down had knocked out all fluorescent lighting and loudspeakers. Lanterns and kitchen stoves still worked — with gas. This brings me back to my original response to the question, what is the most important invention of the past two thousand years. Nothing worth mentioning.

writer and founder and editor of Fiction Magazine

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.

Social & Technology Network Topology Researcher; Adjunct Professor, NYU Graduate School of Interactive Telecommunications Program (ITP); Author, Cognitive Surplus

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.

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

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.

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

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.

Mathematician; Executive Director, H-STAR Institute, Stanford; Author, Finding Fibonacci

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.)

Computational Neuroscientist; Francis Crick Professor, the Salk Institute; Investigator, Howard Hughes Medical Institute; Co-author (with Patricia Churchland), The Computational Brain

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.

a cofounder of GBN, a Partner in the Monitor Group of Companies

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."

Senior Vice President, Product Strategy, Pearson

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.

Physicist, Computer Scientist, Co-Founder, Applied Invention.; Author, The Pattern on the Stone

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.

Associate Professor of Medicine at the National Autonomous University of Mexico

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.

Mathematical Physicist, U.C. Riverside

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?

Executive Editor, The New Yorker

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.

Flutist

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.

Journalist; Author, Us and Them

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.

climatologist, is a professor in the Department of Biological Sciences

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.

Software Engineer, Computer Scientist, Entrepreneur, Philanthropist

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.

Editor-in-Chief of Nature since 1995; Beginning summer 2018, he will become Editor-in-Chief of Springer Nature’s portfolio of journals, books and magazines

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.

Evolutionary Biologist; Emeritus Professor of the Public Understanding of Science, Oxford; Author, Books Do Furnish a Life

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.

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

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.

Director, Center for Science Writings, Stevens Institute of Technology

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.

George Putnam Professor of Biology, Harvard University; Author, From Darwin to Derrida

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.

Psychologist; Visiting Professor, University of Plymouth; Author, Consciousness: An Introduction

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.

physicist, is Associate Vice Provost for Research at Columbia University and was Associate Director of the Superconducting Super Collider Laboratory

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.

member of the External Faculty of the Santa Fe Institute

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.

Classics Scholar, University Librarian, ASU; Author, Pagans

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.

Abby Rockefeller Mauzé Professor of the Social Studies of Science and Technology, MIT; Internet Culture Researcher; Author, The Empathy Diaries

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.

CFO of rightscenter.com, Inc

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.

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

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

Professor of Psychology, Hope College; Co-author, Psychology, 11th Edition

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.

Hobbs Professor of Cognition and Education, Harvard Graduate School of Education; Author, A Synthesizing Mind

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.

Biologist; Senior Science Writer, Bioversity International; Managing Director, Green Ink

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

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

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

Thanks for a stimulating time.

Philosopher; Austin B. Fletcher Professor of Philosophy, Co-Director, Center for Cognitive Studies, Tufts University; Author, From Bacteria to Bach and Back

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.

Information Scientist and Professor of Electrical Engineering and Law, University of Southern California; Author, Noise, Fuzzy Thinking

Most important invention: CALCULUS

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

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

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

Physicist, Institute of Advanced Study; Author, Disturbing the Universe; Maker of Patterns

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.

Professor, Anesthesiology and Psychology Associate Director, Center for Consciousness Studies The University of Arizona Tucson, Arizona

The most important invention in the past two thousand years is anesthesia.

Have you ever had surgery? If so, either a) part of your body was temporarily "deadened" by "local" anesthesia, or b) you "went to sleep" with general anesthesia. Can you imagine having surgery, or needing surgery, or even possibly needing surgery without the prospect of anesthesia? And beyond the agony-sparing factor is an extra added feature — understanding the mechanism of anesthesia is our best path to understanding consciousness.

Anesthesia grew from humble beginnings. Inca shamans performing trephinations (drilling holes in patients' skulls to let out evil humors) chewed coca leaves and spat into the wound, effecting local anesthesia. The systemic effects of cocaine were studied by Sigmund Freud, but cocaine's use as a local anesthetic in surgery is credited to Austrian ophthalmologist Karl Koller who in 1884 used liquid cocaine to temporarily numb the eye. Since then dozens of local anesthetic compounds have been developed and utilized in liquid solution to temporarily block nerve conduction from peripheral nerves and/or spinal cord. The local anesthetic molecules bind specifically on sodium channel proteins in axonal membranes of neurons near the injection site, with essentially no effects on the brain.

On the other hand general anesthetic molecules are gases which do act on the brain in a remarkable fashion — the phenomenon of consciousness is erased completely while other brain activities continue.

General anesthesia by inhalation developed in the 1840's, involving two gases used previously as intoxicants. Soporific effects of diethyl ether ("sweet vitriol") had been known since the 14th century, and nitrous oxide ("laughing gas") was synthesized by Joseph Priestley in 1772. In 1842 Crawford Long, a Georgia physician with apparent personal knowledge of "ether frolics" successfully administered diethyl ether to James W. Venable for removal of a neck tumor. However Long's success was not widely recognized, and it fell to dentist Horace Wells to publicly demonstrate the use of inhaled nitrous oxide for tooth extraction at the Massachusetts General Hospital in 1844. Although Wells had apparently used the technique previously with complete success, during the public demonstration the gas-containing bag was removed too soon and the patient cried out in pain. Wells was denounced as a fake, however two years later in 1846 another dentist William T.G. Morton returned to the "Mass General" and successfully used diethyl ether on patient William Abbott. Morton used the term "letheon" for his then-secret gas, but was persuaded by Boston physician/anatomist Oliver Wendell Holmes (father of the Supreme Court Justice) to use the term anesthesia.

Although its use became increasingly popular, general anesthesia remained an inexact art with frequent deaths due to overdose and effects on breathing until after World War II. Hard lessons were learned following the attack on Pearl Harbor — anesthetic doses easily tolerated by healthy patients had tragic consequences on those in shock due to blood loss. Advent of the endotracheal tube (allowing easy inhalation/exhalation and protection of the lungs from stomach contents), anesthesia gas machines, safer anesthetic drugs and direct monitoring of heart, lungs, kidneys and other organ systems have made modern anesthesia extremely safe. However one mystery remains. Exactly how do anesthetic gases work? The answer may well illuminate the grand mystery of consciousness.

Inhaled anesthetic gas molecules travel through the lungs and blood to the brain. Barely soluble in water/blood, anesthetics are highly soluble in a particular lipid-like environment akin to olive oil. It turns out the brain is loaded with such stuff, both in lipid membranes and tiny water-free ("hydrophobic") lipid-like pockets within certain brain proteins. To make a long story short, Nicholas Franks and William Lieb at Imperial College in London showed in a series of articles in the 1980's that anesthetics act primarily in these tiny hydrophobic pockets in several types of brain proteins. The anesthetic binding is extremely weak and the pockets are only 1 /50 of each protein's volume, so it's unclear why such seemingly minimal interactions should have significant effects. Franks and Lieb suggested the mere presence of one anesthetic molecule per pocket per protein prevents the protein from changing shape to do its job. However subsequent evidence showed that certain other gas molecules could occupy the same pockets and not cause anesthesia (and in fact cause excitation or convulsions). Anesthetic molecules just "being there" can't account for anesthesia. Some natural process critical to consciousness and perturbed by anesthetics must be happening in the pockets. What could that be?

Anesthetic gases dissolve in hydrophobic pockets by extremely weak quantum mechanical forces known as London dispersion forces. The weak binding accounts for easy reversibility - as the anesthetic gas flow is turned off, concentrations drop in the breathing circuit and blood, anesthetic molecules are gently sucked out of the pockets and the patient wakes up. Weak but influential quantum London forces also occur in the hydrophobic pockets in the absence of anesthetics and govern normal protein movement and shape. A logical conclusion is that anesthetics perturb normally occurring quantum effects in hydrophobic pockets of brain proteins.

The quantum nature of the critical effects of anesthesia may be a significant clue. Several current consciousness theories propose systemic quantum states in the brain, and as consciousness has historically been perceived as the contemporary vanguard of information processing (J.B.'s "technology = new perception") the advent of quantum computers will inevitably cast the mind as a quantum process. The mechanism of anesthesia suggests such a comparison will be more than mere metaphor.

Theoretical Neurobiologist; Affiliate Professor Emeritus, University of Washington; Author, Global Fever

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.

Existence is Non-Time, Non-Sequential, and Non-Objective

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

Chief Executive, Medical Research Council;Waynflete Professor of Physiology, University of Oxford

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.

CEO, Socratic Arts Inc.; John Evans Professor Emeritus of Computer Science, Psychology and Education, Northwestern University; Author, Make School Meaningful-And Fun!

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

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

Author, The Math Book, The Physics Book, and The Medical Book trilogy

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."

neurobiologist, is Professor of Biology and Director, Brain and Behaviour Research Group

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

Journalist; Author, Journey to the Edge of Reason

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.

science writer and commentator

Good question!

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

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

Professor of Computer Science, Columbia University; coauthor, Complexity and Information

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.

Founder, TED Conference; EG Conference; TEDMED Conferences; Architect, Cartographer; Author, Information Architects

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

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

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.

Founder, the Whole Earth Catalog; Co-founder, The Well; Co-Founder, The Long Now Foundation, and Revive & Restore; Author, Whole Earth Discipline

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

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

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

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

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

Mathematician; computer scientist; Professor of Media Arts and Sciences, MIT; cofounder, MIT's Artificial Intelligence Laboratory; author, The Emotion Machine

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.

Science Historian; Author, Analogia

The Universal Turing Machine. Because it is universal.

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

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

Nobel Laureate; Physicist

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.

Professor of Interaction Design, Engineering Department, Stanford University

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

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

Professor emeritus, University of New Mexico

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.

Neuroscientist; Professor & Director, Center for Brain and Cognition, UC, San Diego; Author, The Tell-Tale Brain

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