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"What Do You Believe Is True Even Though You Cannot Prove It?"

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Alun Anderson

Chris W. Anderson

Philip W. Anderson

Scott Atran

Simon Baron-Cohen

John Barrow

Gregory Benford

Jesse Bering

Susan Blackmore

Ned Block

Paul Bloom

David Buss

William Calvin

Leo Chalupa

Mihaly Csikszentmihalyi

Paul Davies

Richard Dawkins

Stanislas Deheane

Daniel C. Dennett

Keith Devlin

Jared Diamond

Denis Dutton

Esther Dyson

Freeman Dyson

George Dyson

Jeffrey Epstein

Todd Feinberg

Christine Finn

Kenneth Ford

Howard Gardner

David Gelernter

Neil Gershenfeld

Steve Giddings

Daniel Gilbert

Rebecca Goldstein

Daniel Goleman

Brian Goodwin

Alison Gopnik

Jonathan Haidt

Haim Harari

Judith Rich Harris

Sam Harris

Marc D. Hauser

Marti Hearst

W. Daniel Hillis

Donald Hoffman

John Horgan

Verena Huber-Dyson

Nicholas Humphrey

Piet Hut

Stuart Kauffman

Alan Kay

Kevin Kelly

Stephen Kosslyn

Kai Krause

Lawrence Krauss

Ray Kurzweil

Jaron Lanier

Leon Lederman

Janna Levin

Joseph LeDoux

Seth Lloyd

Benoit Mandelbrot

Gary Marcus

Lynn Margulis

John McCarthy

Pamela McCorduck

Ian McEwan

John McWhorter

Thomas Metzinger

Oliver Morton

David Myers

Randolph Nesse

Tor Nørretranders

Martin Nowak

James O'Donnell

Alex Pentland

Irene Pepperberg

Stephen Petranek

Clifford Pickover

Steven Pinker

Jordan Pollack

Carolyn Porco

Robert R. Provine

Martin Rees

Howard Rheingold

Carlo Rovelli

Rudy Rucker

Douglas Rushkoff

Karl Sabbagh

Robert Sapolsky

Roger Schank

Jean Paul Schmetz

Stephen H. Schneider

Gino Segre

Martin E. P. Seligman

Terrence Sejnowski

Rupert Sheldrake

Michael Shermer

Charles Simonyi

John R. Skoyles

Lee Smolin

Elizabeth Spelke

Maria Spiropulu

Tom Standage

Paul Steinhardt

Bruce Sterling

Leonard Susskind

Nassim Taleb

Timothy Taylor

Arnold Trehub

Robert Trivers

J. Craig Venter

Alexander Vilenkin

Margaret Wertheim

Donald I. Williamson

Ian Wilmut

Ellen Winner

Anton Zeilinger


Psychologist, New York University; Author, The Birth of the Mind

If computers are made up of hardware and software, transistors and resistors, what are neural machines we know as minds made up of?

Minds clearly are not made up of transistors and resistors, but I firmly believe that at least one of the most basic elements of computation is shared by man and machine: the ability to represent information in terms of an abstract, algebra-like code.

In a computer, this means that software is made up of hundreds, thousands, even millions of lines that say things like IF X IS GREATER THAN Y, DO Z, or CALCULATE THE VALUE OF Q BY ADDING A, B, AND C. The same kind of abstraction seems to underlie our knowledge of linguistics. For instance, the famous linguistic dictum that a Sentence consists of a Noun Phrase plus a Verb Phrase can apply to an infinite number of possible nouns and verbs, not just a few familiar words. In its open-endedness, it is an example of mental algebra par excellence.

In my lab, we discovered that even infants seem to be able to grasp something quite similar. For example, in the course of just two minutes, a seven-month-old baby can extract the ABA "grammar" inherent in set of made-up sentences like la ta la, ga na ga, je li je. Or the ABB "grammar" in sentences like la ta ta, ga na na, je li li.

Of course, this experiment doesn't prove that there is an "algebra" circuit in the brain—psychological techniques alone can't do that. For final proof, we'll need neuroscientific techniques far more sophisticated than contemporary brain imaging, such that we can image the brain at the level of interactions between individual neurons. But every bit of evidence that we can collect now—from babies, from toddlers, from adults, from psychology and from linguistics—seems to confirm the idea that algebra-like abstraction is a fundamental component of thought.

Writer and Television Producer; Author, The Riemann Hypothesis

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.

Anthropologist, University of Michigan; Author, In God's We Trust

There is no God that has existence apart from people's thoughts of God. There is certainly no Being that can simply suspend the (nomological) laws of the universe in order to satisfy our personal or collective yearnings and whims—like a stage director called on to change and improve a play. But there is a mental (cognitive and emotional) process common to science and religion of suspending belief in what you see and take for obvious fact. Humans have a mental compulsion—perhaps a by-product of the evolution of a hyper-sensitive reasoning device to serve our passions—to situate and understand the present state of mundane affairs within an indefinitely extendable and overarching system of relations between hitherto unconnected elements. In any event, what drives humanity forward in history is this quest for non-apparent truth.

Psychologist, University of Arkansas

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.

Research Scientist, MIT School of Architecture and Planning; Author, The Alex Studies

I believe, but can't prove, that human language evolved from a combination of gesture and innate vocalizations, via the concomitant evolution of mirror neurons, and that birds will provide the best model for language evolution.  

Work on mirror neurons over the past decade has provided intriguing evidence, although no solid proof, for the gestural origins of speech. What can be called the mirror neuron hypothesis(MNH) suggests that only a small re-organization of the nonhuman primate brain was needed to create the wiring that underlies speech acquisition/learning. What is missing from the MNH is a model of the development of language from speech; it is here that I believe that a model based on avian vocalizations is most valuable.

First, some background. Passerine birds can be divided into two groups: the oscines, who learn their songs, and the sub-oscines, who have a limited number of what seem to be innately-specified songs; the former have a well-defined neural architectures and mechanisms for song acquisition; the latter lack brain structures for song acquisition, although they obviously have brain and vocal tract structures for producing song. The sub-oscines, in parallel with nonhuman primates, often use various activities or gestures (posture, numbers of repetitions of songs, feather erectness, types of flights, etc) to provide additional information about the meaning of their utterances. W. John Smith, for example, can predict a flycatchers actions by the combination of posture, flight, and singing pattern he observes. The songbirds, like human children learning language, will not learn their vocalizations if deafened, and need to hear, babble and practice songs before attaining adult competence; very recent work by Rose et al. demonstrate that even the syntax of their song is learned through early exposure to paired phrases, which are then combined to create the adult vocalizations. Such data, demonstrating how sparrows integrate information about temporally-related events and how they use that information to develop sequential vocal behavior, is a viable model for human syntax acquisition.

Now, no one knows if any birds have any mirror neurons, and how their mirror neurons would function if they did exist; some neural data on responses to self-song provide intriguing hints but go no further. I predict (a) the existence of such neurons in oscines and (b) that such neurons will have a robust role in oscine song development, but (c) that only more primitively-functioning mirror neurons (akin to the differences separating monkey and human MNs) will be found in sub-oscines.

Now, what about the so-called missing link between learned and unlearned vocal behavior? No one has found such a missing link in the primate line. But Donald Kroodsma has recently discovered a flycatcher (a supposedly sub-oscine bird) that apparently learns its song. The song is simple, but has variations among groups of birds that constitute dialects. No one yet knows if these birds have brain mechanisms for song learning, or what these mechanisms might be. But I predict that Kroodsma's flycatchers will have mirror neurons that function in intermediate manner, between those of the oscines and sub-oscines, and will provide a model for the missing link between nonhuman primate and human communication.

Mathematical trader; Author, Fooled By Randomness

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.

Psychiatrist and Neurologist, Albert Einstein College of Medicine; Author, Altered Egos

I believe the human race will never decide that an advanced computer possesses consciousness. Only in science fiction will a person be charged with murder if they unplug a PC. I believe this because I hold, but cannot yet prove, that in order for an entity to be consciousness and possess a mind, it has to be a living being.

Being alive, of course, does not guarantee the presence of a mind. For example, a plant carries on the necessary metabolic functions to be alive, but still does not possess a mind. A chimpanzee, on the other hand, is a different story. All the behavioral features we share with chimps in addition to life, such as intelligence, the ability to deceive, mirror self-recognition, some individual social identity, make chimps seem so much like us that many in the scientific community intuitively grant chimps "beinghood" and consciousness.

In addition to being alive, therefore, it appears that a living thing must be a being, must possess a self, to possess a mind. But silicon chips are not alive, and computers are not beings. I argue that this is so because the particular material substance and arrangement of the brain is essential to the creation of consciousness and "beinghood." Computers will never achieve consciousness because in order for a computer to be "conscious like us" it will need to be made of living stuff like us, to grow like us, and unfortunately, to be able to die like us.

Software: Concepts, Artwork & Interface Design; Byteburg Research Lab above the Rhein River

I always felt, but can't prove outright: Zen is wrong. Then is right.
Everything is not about the now, as in the "here and how", "living for the moment" On the contrary: I believe everything is about the before then and the back then.

It is about the anticipation of the moment and the memory of the moment, but not the moment.

In German there is a beautiful little word for it: "Vorfreude", which still is a shade different from "delight" or "pleasure" or even "anticipation". It is the "Pre-Delight", the "Before-Joy", or as a little linguistic concoction: the "ForeFun"; in a single word trying to express the relationship of time, the pleasure of waiting for the moment to arrive, the can't wait moments of elation, of hoping for some thing, some one, some event to happen.

Whether it's on a small scale like that special taste of your favorite food, waiting to see a loved one, that one moment in a piece of music, a sequence in a movie....or the larger versions: the expectation of a beautiful vacation, the birth of a baby, your acceptance of an Oscar.

We have been told by wise men, Dalais and Maharishis that it is supposedly all about those moments, to cherish the second it happens and never mind the continuance of time...

But for me, since early childhood days, I realized somehow: the beauty lies in the time before, the hope for, the waiting for, the imaginary picture painted in perfection of that instant in time. And then, once it passes, in the blink of an eye, it will be the memory which really stays with you, the reflection, the remembrance of that time. Cherish the thought..., remember how....

Nothing ever is as beautiful as its abstraction through the rose-colored glasses of anticipation...The toddlers hope for Santa Claus on Christmas eve turns out to be a fat guy with a fashion issue. Waiting for the first kiss can give you waves of emotional shivers up your spine, but when it then actually happens, it's a bunch of molecules colliding, a bit of a mess, really.  It is not the real moment that matters. In Anticipation the moment will be glorified by innocence, not knowing yet. In Remembrance the moment will be sanctified by memory filters, not knowing any more.

In the Zen version, trying to uphold the beauty of the moment in that moment is in my eyes a sad undertaking. Not so much because it can be done, all manner of techniques have been put forth how to be a happy human by mastering the art of it.  But it also implies, by definition, that all those other moments live just as much under the spotlight: the mundane, the lame, the gross, the everyday routines of dealing with life's mere mechanics.

In the Then version, it is quite the opposite: the long phases before and after last hundreds or thousands of times longer than the moment, and drown out the everyday humdrum entirely.

Bluntly put: spend your life in the eternal bliss of always having something to hope for, something to wait for, plans not realized, dreams not come true.... Make sure you have new points on the horizon, that you purposely create. And at the same time, relive your memories, uphold and cherish them, keep them alive and share them, talk about them.

Make plans and take pictures.

I have no way of proving such a lofty philosophical theory, but I greatly anticipate the moment that I might... and once I have done it, I will, most certainly, never forget.

Psychologist, Harvard University

I believe, first, that all people have the same fundamental concepts, values, concerns, and commitments, despite our diverse languages, religions, social practices, and expressed beliefs. If defenders and opponents of abortion, Israelis and Palestinians, or Cambridge intellectuals and Amazonian jungle dwellers were to get beyond their surface differences, each would discover that the common ground linking them to members of the other group equals that which binds their own group together. Our common conceptual and moral commitments spring from the core cognitive systems that allow an infant to grow rapidly and spontaneously into a competent participant in any human society.

Second, one of our shared core systems centers on a notion that is false: the notion that members of different human groups differ profoundly in their concepts and values. This notion leads us to interpret the superficial differences between people as signs of deeper differences. It has quite a grip on us: Many people would lay down their lives for perfect strangers from their own community, while looking with suspicion at members of other communities. And all of us are apt to feel a special pull toward those who speak our language and share our ethnic background or religion, relative to those who don't.

Third, the most striking feature of human cognition stems not from our core knowledge systems but from our capacity to rise above them. Humans are capable of discovering that our core conceptions are false, and of replacing them with truer ones. This change has happened dramatically in the domain of astronomy. Core capacities to perceive, act on, and reason about the surface layout predispose us to believe that the earth is a flat, extended surface on which gravity acts as a downward force. This belief has been decisively overturned, however, by the progress of science. Today, every child who plays computer games or watches Star Wars knows that the earth is one sphere among many, and that gravity pulls all these bodies toward one another.

Together, my three beliefs suggest a fourth. If the cognitive sciences are given sufficient time, the truth of the claim of a common human nature eventually will be supported by evidence as strong and convincing as the evidence that the earth is round. As humans are bathed in this evidence, we will overcome our misconceptions of human differences. Ethnic and religious rivalries and conflicts will come to seem as pointless as debates over the turtles that our pancake earth sits upon, and our common need for a stable, sustainable environment for all people will be recognized. But this fourth belief is conditional. Our species is caught in a race between the progress of our science and the escalation both of our intergroup conflicts and of the destructive means to pursue them. Will humans last long enough for our science to win this race?

Neuroscience Researcher; Author, The End of Faith

Twenty-two percent of Americans claim to be certain that Jesus will return to earth to judge the living and the dead sometime in the next fifty years. Another twenty-two percent believe that he is likely to do so. The problem that most interests me at this point, both scientifically and socially, is the problem of belief itself. What does it mean, at the level of the brain, to believe that a proposition is true? The difference between believing and disbelieving a statement—Your spouse is cheating on you; you've just won ten million dollars—is one of the most potent regulators of human behavior and emotion. The instant we accept a given representation of the world as true, it becomes the basis for further thought and action; rejected as false, it remains a string of words.

What I believe, though cannot yet prove, is that belief is a content-independent process. Which is to say that beliefs about God—to the degree that they are really believed—are the same as beliefs about numbers, penguins, tofu, or anything else. This is not to say that all of our representations of the world are acquired through language, or that all linguistic representations are on the same logical footing. And we know that different regions of the brain are involved in judging the truth-value of statements drawn from different content domains. What I do believe, however, is that the neural processes that govern the final acceptance of a statement as "true" rely on more fundamental, reward-related circuitry in our frontal lobes—probably the same regions that judge the pleasantness of tastes and odors. Truth may be beauty, and beauty truth, in more than a metaphorical sense. And false statements may, quite literally, disgust us.

Once the neurology of belief becomes clear, and it stands revealed as an all-purpose emotion arising in a wide variety of contexts (often without warrant), religious faith will be exposed for what it is: a humble species of terrestrial credulity. We will then have additional, scientific reasons to declare that mere feelings of conviction are not enough when it comes time to talk about the way the world is. The only thing that guarantees that (sufficiently complex) beliefs actually represent the world, are chains of evidence and argument linking them to the world. Only on matters of religious faith do sane men and women regularly dispute this fact. Apart from removing the principle reason we have found to kill one another, a revolution in our thinking about religious belief would clear the way for new approaches to ethics and spiritual experience. Both ethics and spirituality lie at the very heart of what is good about being human, but our thinking on both fronts has been shackled to the preposterous for millennia. Understanding belief at the level of the brain may hold the key to new insights into the nature of our minds, to new rules of discourse, and to new frontiers of human cooperation.

Biologist, University of Massachusetts, Amherst; Author, Symbiosis in Cell Evolution.

I feel that I know something that will turn out to be correct and eventually proved to be true beyond doubt


That our ability to perceive signals in the environment evolved directly from our bacterial ancestors. That is, we, like all other mammals including our apish brothers detect odors, distinguish tastes, hear bird song and drum beats and we too feel the vibrations of the drums. With our eyes closed we detect the light of the rising sun. These abilities to sense our surroundings are a heritage that preceded the evolution of all primates, all vertebrate animals, indeed all animals. Such sensitivities to wafting plant scents, tasty salted mixtures, police cruiser sirens, loving touches and star light register because of our "sensory cells".

These avant guard cells of the nasal passages, the taste buds, the inner ear, the touch receptors in the skin and the retinal rods and cones all have in common the presence at their tips of projections ("cell processes") called cilia. Cilia have a recognizable fine structure. With a very high power ("electron") microscope a precise array of protein tubules, nine, exactly nine pairs of tubules are arranged in a circular array and two singlet tubules are in the center of this array. All sensory cells have this common feature whether in the light-sensitive retina of the eye or the balance-sensitive semicircular canals of the inner ear. Cross-section slices of the tails of human, mouse and even insect (fruit-fly) sperm all share this same instantly recognizable structure too. Why this peculiar pattern? No one knows for sure but it provides the evolutionist with a strong argument for common ancestry. The size (diameter) of the circle (0.25 micrometers) and of the constituent tubules (0.024 micrometers) aligned in the circle is identical in the touch receptors of the human finger and the taste buds of the elephant.

What do I feel that I know, what Oscar Wilde said (that "even true things can be proved")?

Not only that the sensory cilia derive from these exact 9-fold symmetrical structures in protists such as the "waving feet" of the paramecium or the tail of the vaginal-itch protist called Trichomonas vaginalis. Indeed, all biologists agree with the claim that sperm tails and all these forms of sensory cilia share a common ancestry.

But I go much farther. I think the the common ancestor of the cilium, but not the rest of the cell, was a free-swimming entity, a skinny snake-like bacterium that, 1500 million years ago squiggled through muds in a frantic search for food. Attracted by some smells and repelled by others the bacteria, by themselves, already enjoyed a repertoire of sensory abilities that remain with their descendants to this day. In fact, this bacterial ancestor of the cilium never went extinct, rather some of its descendants are uncomfortably close to us today. This hypothetical bacterium, ancestor to all the cilia, was no ordinary rod-shaped little dot.

No, this bacterium who still has many live relatives, entered into symbiotic partnerships with other very different kinds of bacteria. Together this two component partnership swam and stuck together both persisted. What kind of bacterium became an attached symbiont that impelled its partner forward? None other than a squirming spirochete bacterium.

The spirochete group of bacteria includes many harmless mud-dwellers but it also contains a few scary freaks: the treponeme of syphilis and the borrelias of Lyme disease. We animals got our exquisite ability to sense our surroundings—to tell light from dark, noise from silence, motion from stillness and fresh water from brackish brine—from a kind of bacterium whose relatives we despise. Cilia were once free-agents but they became an integral part of all animal cells. Even though the concept that cilia evolved from spirochetes has not been proved I think it is true. Not only is it true but, given the powerful new techniques of molecular biology I think the hypothesis will be conclusively proved. In the not-too-distant future people will wonder why so many scientists were so against my idea for so long!

Physicist, UC Irvine; Author, Deep Time

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?

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