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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Will we live to see the components of the electron?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mental processes: An out-of-body existence?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Progress. 

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

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

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

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

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

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

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

Tribal Mind.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

I like to think there may be such a law.

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

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

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

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

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

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

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

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

Why is there scientific law at all?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

We are good at fitting explanations to the past, all the while living in the illusion of understanding the dynamics of history.

My claim is about the severe overestimation of knowledge in what I call the " ex post" historical disciplines, meaning almost all of social science (economics, sociology, political science) and the humanities, everything that depends on the non-experimental analysis of past data. I am convinced that these disciplines do not provide much understanding of the world or even their own subject matter; they mostly fit a nice sounding narrative that caters to our desire (even need) to have a story. The implications are quite against conventional wisdom. You do not gain much by reading the newspapers, history books, analyses and economic reports; all you get is misplaced confidence about what you know. The difference between a cab driver and a history professor is only cosmetic as the latter can express himself in a better way.

There is convincing but only partial empirical evidence of this effect. The evidence can only be seen in the disciplines that offer both quantitative data and quantitative predictions by the experts, such as economics. Economics and finance are an empiricist's dream as we have a goldmine of data for such testing. In addition there are plenty of "experts", many of whom make more than a million a year, who provide forecasts and publish them for the benefits of their clients. Just check their forecasts against what happens after. Their projections fare hardly better than random, meaning that their "stories" are convincing, beautiful to listen to, but do not seem to help you more than listening to, say, a Chicago cab driver. This extends to inflation, growth, interest rates, balance of payment, etc. (While someone may argue that their forecasts might impact these variables, the mechanism of "self-canceling prophecy" can be taken into account). Now consider that we depend on these people for governmental economic policy!

This implies that whether or not you read the newspapers will not make the slightest difference to your understanding of what can happen in the economy or the markets. Impressive tests on the effect of the news on prices were done by the financial empiricist Victor Niederhoffer in the 60s and repeated throughout with the same results.

If you look closely at the data to check the reasons of this inability to see things coming, you will find that these people tend to guess the regular events (though quite poorly); but they miss on the large deviations, these " unusual" events that carry large impacts. These outliers have a disproportionately large contribution to the total effect.

Now I am convinced, yet cannot prove it quantitatively, that such overestimation can be generalized to anything where people give you a narrative-style story from past information, without experimentation. The difference is that the economists got caught because we have data (and techniques to check the quality of their knowledge) and historians, news analysts, biographers, and "pundits" can hide a little longer. Basically historians might get a small trend here and there, but they did miss on the big events of the past centuries and, I am convinced, will not see much coming in the future. It was said: "the wise see things coming". To me the wise persons are the ones who know that they can't see things coming.

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

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

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

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

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

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

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

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

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

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

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

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

We're living longer, and thinking shorter.

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

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

It's all about time.

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

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

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

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

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

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

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

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

How can we reverse this?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

So the answer is still...nothing.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

I believe that microbial life exists elsewhere in our galaxy.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Of course, I could be wrong...

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

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

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

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

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

Breaking the brain's modularity.

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

Spontaneous activity and the autonomy of consciousness.

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

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

The profound influence of culture on the human brain.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Here are three of my unproven beliefs:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Think true, cannot prove. 

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

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

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

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

I think human-level artificial intelligence will be achieved.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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