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Lucidity and scienceIII: Hypercredulity, quantum mechanics,and scientific truth

PROFESSOR MICHAEL E. McINTYRECentre for Atmospheric Science at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK

Scientific research can reasonably be described as a search for truth, in an important and nontrivial sense. Butrespect for the scientific ideal is incompatible with the myth, or instinctive, quasi-religious belief, that science isabout discovering final, infallible, absolute or ultimate truth. That myth, if publicly endorsed by scientists,inadvertently or otherwise, is perilous because it fuels tribal conflicts like the current 'science wars' and increasespublic confusion about science. This in turn helps the psychological, social, and economic forces, including theforces within big commerce, that work toward discrediting the scientific ideal and ethic for reasons both consciousand unconscious, restricting our options for coping with an uncertain and highly dangerous future. Future possibilitiesinclude the risk of substantial sea level rise, continuing unstoppably for a century or more after first detection.Also possible - and arguably likely if the scientific ideal is too far discredited - is the destruction of the system offree market democracy and free trade, the government by consent and prosperity of individuals on which bigcommerce itself depends.

Our understanding of the actual and potential human behaviour patterns that might lead to such destruction isbeing sharpened by evidence from linguistics, palaeoclimatology, palaeoanatomy, and genetics, and from researchon perception and cognition. It is remarkable that any such self-understanding is possible for us, and even moreremarkable that any human society allows such matters to be openly discussed. Both things demonstrate ourspecies' adaptability and the power of cultural evolution - more precisely the adaptive power of the intimate andintricate interplay, or dynamic, of what we falsely dichotomise as 'nature and nurture'. This adaptive power is onereason why our children and their descendents might dare, against the odds, to hope for some kind of civilisedfuture existence incorporating a new covenant between science and society.

'I would know my shadow and my light, so shall 1 at last be whole.'Michael Tippett128

Respect for science is on trial in today's world. Thisis not only trial by soundbite but also, more to thepoint, trial by our deepest fears and imaginings. 129,130Paradoxically, it is the same world where sciencehas made it possible for all children to be wantedchildren, 131 where the economic running is beingmade by scientifically minded competitors, andwhere scientific skills and knowledge are crucialto meeting the growing threats from poverty, war,terrorism, environmental change, and new diseaseepidemics. 132,133

Like it or not, science and technology are increas-ingly powerful tools for good and evil. Human societ-ies, especially those with democratic aspirations, needsome understanding of the tools they use. If today'sdemocracies are to survive as democracies they willneed to find ways of alleviating the widespread,profound, and dangerous confusion 134,135 about whatscience is and what it is not, and about the value ofscience to society. That value includes the humanvalue of the scientific ideal, meaning the ideal in thesense discussed in Parts I and II of this series136 - avalue now largely neglected and perhaps even largelyunrecognised by today's societies, as expressed

1998 The Institute of Materials

officially by trends in science policymaking and audit-ing. I shall argue that this puts us in far greater perilthan is commonly believed.

Understanding the reasons for the peril requiresan interdisciplinary perspective. This article will tryto sketch what seems to be involved. Alongside wellknown themes there are some new twists, comingfrom recent discoveries in linguistics and palaeoclima-tology and from insights into perception and cog-nition, plus evidence from palaeoanatomy andgenetics. There are increasingly clear implications notonly for science po1icymaking and auditing but alsofor education, and for scientists' professional codesof conduct.

Ideal and methodI shall refer below to the sceptical questions askedby thoughtful and intelligent non-scientists. Some ofthose questions indicate a confusion for which we asscientists are in part to blame: a confusion betweenthe scientific ideal, on the one hand, and humanattempts to approach it on the other. These two verydifferent things tend to be lumped together whenspeaking of 'science' or 'the scientific method'.

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Even professional historians of science have some-times lost sight of the ideal in their attempts tounderstand the complexities, imperfections, and falli-bilities - indeed, the sheer stubborn difficulties - ofhuman attempts to approach the ideal while strug-gling with uncertainty at the periphery of scientificknowledge. That struggle, indeed the whole sociologyand psychology of research, is an important butseparate aspect of science.137 It is something thatneeds to be clearly distinguished from the scientificideal. It involves of course human error, moral issues,varying standards of personal behaviour, powergames played by scientists and non-scientists, band-wagon effects and so called paradigm changes, everincreasing cultural and commercial pressures, varyinglevels of numinous or religious feeling, and certainlyno single, rigid, infallible methodology. Althoughthere are good practical working rules tested by harshexperience, 'the scientific method' - unlike the scien-tific ideal - is not, never was, nor is ever likely to be,a rigidly defined entity let alone something that issimple to explain.

Let me try to put the last point more sharply. It isa dangerous illusion to think that there is a rigidlyand explicitly defined 'method' guaranteed to produceaccurate scientific judgments on demand, let alone todo so before the next quarterly financial report. Ifthere were such a method, then science would be bestturned over to computers. Anyone who has donesignificant scientific research knows that there is nogenerally applicable 'method' in that sense, especiallywhen we are dealing with the unknown and theunpredictable - as with, for example, the evolutionaryresponse of bacteria to antibiotics,132 and the emerg-ence of new disease agents in response to pollu-tion.138,139Disease agents know nothing of financialreports. They are massively parallel problem solversthat in some sense know about, and try to adapt to,the temperatures, chemicals, and life forms in theirchanging environments.

There is a fundamental reason why scientific'method' cannot be rigidly and legalistically defined.If you accept the hypothesis that both science andordinary perception work by model fitting, and there-fore involve combinatorial tree pruning, then it fol-lows, for the reasons discussed in Parts I and II -including the largeness of combinatorially largenumbers - that even the most rigorous, the mostmeticulous scientific thinking has an inescapableunconscious component. It is not just that some ofthe modelling assumptions happen to be unconscious:a good many are bound to be unconscious. The'walking lights' phenomenon is a simple but sufficientillustration,136 and there are countless others.140

The model fitting hypothesis explains why scientificand technological breakthroughs, and much ordinaryscientific progress as well, often come from exposing,from making conscious, a previously unconsciousassumption, from breaking out of what psychologistscall a mental tunnel. 140,141This means unpruningsome branch of a combinatorially large tree of pos-

30 INTERDISCIPLINARY SCIENCE REVIEWS, 1998, VOL 23, NO. 1

sibilities.142 If the branch comes from far enoughdown the tree then we tend to speak of a break-through or even a paradigm change.141

I want to make a case for talking less often aboutthe scientific method, in public at least, and moreoften about the scientific ideal. As already hinted,remembering the ideal is important for a simplereason that transcends technicalities. Forgetting it islikely to have catastrophic consequences for human-kind, for our increasingly crowded planet andourselves. New evidence about our distant past under-lines this point, as will be seen shortly. And a widerappreciation of the scientific ideal and its significanceis surely attainable, because it is fundamentally asimple matter, and because there is genuine publicinterest. Such appreciation could help to answer orforestall the sceptical questions asked by thoughtfuland intelligent non-scientists. It could help to counterthe widespread, and in some ways understandable,talk about the end of science, the failure of science,the arbitrariness, the inhumanity, the imperialism,the evil, the loathsomeness of science,143and so forth.

There is, of course, nothing arcane or technicallycomplicated about the scientific ideal. Difficult thoughit may be to approach, it should be easy to explain -to ourselves, to our students, and to others. Suchexplanations have been given before, and they willhave to be given again.

One might try saying, for instance, that respect forthe scientific ideal is like caution in buying a usedcar,135or like the attitude of a Miss Marple trying tosolve a murder mystery. I was going to say SherlockHolmes, except that he is far too sure about seeingall the possibilities. It is like the sceptical juror'sattitude in the film 'Twelve Angry Men', the jurorwho insisted on taking another look at the evidencein a murder trial when everyone else thought theyknew the truth. One might say that it is like Spock'sattitude in 'Star Trek', if you like 'Star Trek', thoughnothing to do with the flashing lights144- and nothingto do with comic strip pictures of spitting sparks,bubbling beakers, monster mutants, and madscientists.

Respect for the scientific ideal is something verysane, close to common sense even though much morecareful.145It is an attitude that tries hard to keep anopen mind while deploying logical thinking as care-fully as possible. It puts up with nagging uncertainty.It is willing to admit ignorance. It avoids priorjudgments about candidate theories or hypotheses,that is, about candidate models, and it avoids priorjudgments about methodologies and domains ofapplicability, apart from giving primacy to the coher-ence and self consistency of a model and its goodnessof fit to experimental data. It is sceptical about anyother reasons to favour a model, apart from thecautious application of Occam's razor, or explanatoryparsimony, the principle that a model should be nomore complicated than necessary.

It asks, what happens to the goodness of fit whennew data become available? Does the whole thing

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withstand being looked at from another viewpoint?Does it withstand all the consistency checks anyonecan think of? (That is why thought experiments, 146as well as mathematics and computer simula-tions,136,142,147are so important in science.) Howaccurate is the fit? How good are the data? Does thetheory, the model being tested, need to be changed,or thrown out altogether - do we need some large orsmall paradigm change, or novel viewpoint as it usedto be called - or does the experimental error or theexperimental concept need further investigation? AmI measuring what I think I am measuring?

Just as with the model fitting process underlyingordinary perception, these are all questions aboutaccuracy or goodness of fit, and about repeatedchecking in different ways. They are about taking yetanother look from yet another angle146 or, so tospeak, listening or feeling as well as looking, and notabout any absolute and knowably final truth of thetheory. 'If it looks like a duck, quacks like a duck,and waddles like a duck, let's see if it swims like aduck and dives like a duck.' Even in those remarkablecases in physics where a beautifully simple theoryrepeatedly fits high precision data to many decimalplaces - including data obtained after theoreticalpredictions are made - we can never, if we respectthe scientific ideal, claim to know with certainty thatany such theory represents an absolute truth, eventhough we can reasonably and provisionally say thatsuch a theory must, in some sense, be close to reality,or 'close to the truth' .148

It is indeed remarkable - not to say awesome -how well Occam's razor seems to work in some casesat least: how reliable, accurate, and widely applicablea simple model can be, and how beautiful andinsightful. Einstein's gravitational theory is a goodexample, and a supremely beautiful one.149There canbe no doubt that the skilful use of Occam's razor,and the faith in Occam's razor, has had a crucial rolein the discovery of such models.147,149,150But noneof this implies the possibility of access to a final andabsolute truth that is known for certain or could,even in principle, be known for certain.

I shall return to this point because, though it maysound to some like philosophical hair splitting andto others like repeating the obvious, and though ithas often been made before, the point is too importantto be left aside. It is an essential part of what I amcalling the scientific ideal, and I believe central tosolving the problems labelled 'science wars' and'public understanding', beginning at primary schoollevel.151I think the point should be made as oftenand as cogently as possible, especially by scientists inthe public eye. In today's conditions it is arguablythe most crucial single point to get over to non-scientists, when trying to improve the public under-standing of science and when trying to discouragethe misuse of science, as with

X is Absolutely Safe.

For reasons to be explained I think it is the point

whose neglect, in the long run, most deeply anddangerously undermines respect for the scientific idealand reduces the value of the ideal to society, not leastthe human value in a far reaching sense.

The value of the scientific idealBut what is it, then, this value to society, this humanvalue, of the scientific ideal? Contrary to popularmythology, it is not only the value of cheap longdistance communication, painless dentistry, heartpacemakers, and the like. It is not only the value ofthe invisible science base, the unmeasurable infra-structure of tacit skills and mental flexibility152required to reach and make use of tomorrow'snew knowledge, new understanding, and new tech-nologies, a prerequisite to future developments ofpractical and economic value - such as the mainten-ance or improvement of food safety, the mitigationor prevention of the new disease epidemics, thehumane avoidance of overpopulation and environ-mental stress, the development of robustness, security,maintainability, reliability, and audit ability ofcomputer software and electronic transaction sys-tems,153,154the efficient and sustainable use of energyand other resources,155,156the containment of terror-ism,157 the early detection of environmental change- the value of good science and technology as oureyes and ears on an uncertain future, without whichour heads, and our leaders' heads, will be firmlyburied in the sand, at great future COSt.131,132,158Norindeed is it only the invisible and unmeasurablecultural value, the value of the intellectual thrill andastonishment of great discoveries and great leaps ofthe imagination, and the spiritual value of somethingthat transcends the individual:

Then felt I like some watcher of the skiesWhen a new planet swims into his ken ... - John Keats159

Of course, it is all of these. But it is also somethingstill less visible and still less measurable, though stillmore crucial and still more valuable - in a hardeconomic sense. It is the value, beyond price, ofrespect for the scientific ideal, if such respect can bemaintained, as a moderating or countervailing force,or if you will an insurance, against renewed cycles ofsocial chaos and totalitarian repression in a worldfull of modern weapons, biological, physical,chemical, psychological, and economic155 - aninsurance against what today's politicians might callwealth destruction, on a gigantic scale, a scale incalcu-lably greater than the recent wealth destruction byfood safety scares.139 This is an insurance againstwealth destruction on the scale of gross nationalproducts, an insurance against the breakdown ofdemocracy itself, of government by consent, of freetrade and personal prosperity - the breakdownof the increasingly fragile economic, technological,and psychological infrastructures of modern humansocieties - an insurance whose premiums are dwarfedby the cost /of the disasters insured against. It is a

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1800

1600Later period of rapid

~brain evolution

~ 1400 /C")~~

E()'-" 1200~~ I=J~13 as a. 1000 a1 Earlier period of rapid() brain evolution15 / 2 800 CU .- *..0 * *600 * **+-++~ + + ++

400 + + + +

2000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5Age In millions of years

+ australopithecines; * early Homo (H. habilis, H. rudolfensis); Homo erectus, including Homo ergaster;o archaic and modern Homo

1 Skull capacities of some of our ancestors and their close relatives, from the fossil record. Reference 173,from which the figure is taken with kind permission, reviews this and several other lines of palaeo-anatomical evidence that are consistent with an evolutionary preconditioning for language, intensify-ing roughly 2000 millennia ago (see text), followed by the rapid co-evolution of brain and language overthe past few hundred millennia in a genetic-memetic 'evolutionary arms race,161,174

long term insurance whose value might commandsignificant public understanding, if explained wellenough. It has not, I think, been explained nearlywell enough in recent years, because its value, thoughlong recognised by careful thinkers,160 now seems tobe forgotten not only in popular mythology but also,I shall argue, in today's official science policymaking.

This forgetfulness seems to be connected in partwith the workings of the short sighted, not to sayblind, international market forces that seem to domi-nate our situation today, and to which I shall alsorefer, the very forces whose enormous strength makesus forget that they too are vulnerable - that themarkets themselves depend for their wealth creatingpotential on the avoidance of social chaos and totali-tarian repression.

But how can respect for the scientific ideal besocially stabilising, rather than destabilising as somewould now have us believe? As long recognised bycareful thinkers, something very fundamental isinvolved, something both visible and invisible. It issomething about our own human nature that weseem close to understanding quite well, and thatwe need to understand, in any case, as well aspossible. It is a matter of ubiquitous psychologicalrealities, of human instincts, of our unalterable gen-etic inheritance,161,162 part of what our politiciansboth underestimate163 and perilously exploit. Respectfor the scientific ideal cannot solve all our problems,but it can help with 'clearing space to speak of the

32 INTERDISCIPLINARY SCIENCE REVIEWS, 1998, VOL. 23, NO.1

unspeakable',164 with tipping the balance - as hasalready happened so remarkably in recent centuries- toward -understanding, moderating, and redirectingsome of the most terrible and potent forces that leadto social instability.

These forces manifest themselves most plainly, aseveryone knows, in the phenomena called bigotryand superstition, sectarianism and racism, scape-goating and witch hunting,165 kamikaze terrorismand other forms of human sacrifice,166 and genocidalwarfare. They are forces whose crosscultural presenceand whose potential for social catastrophe have beenamply and repeatedly demonstrated throughout his-tory, and in recent living memory. I shall hypothesisethat they involve what is usually called 'instinctive'behaviour,167 as well as cultural influence - moreaptly nature-nurture or genetic-memetic168 inter-actions, the intricate, inextricable interplay of genomeand culture161,167,169-171- and I assume that they arelatent in everyone and could easily be powerfulenough to destroy democracies and free market econ-omies of the type now familiar, which, throughouthuman existence, have not, after all, been among theusual types of human society,172 especially underenvironmental stress.

Language and climateWhat then is fundamental? To get a clearer view ofthis, I must digress on language and climate. We

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Wernicke's area

2 Side view of, and cut through, the brain of arighthanded modern human: after Ref. 175.Thecut, more precisely a view from above of thepart of the brain below the cut, shows some ofthe left-right asymmetry including the largeWernicke's area (shading at left), essential tounderstanding language. The patterns of foldsor sulci and their evolution over the timespanof Fig. 1 can be traced in fossil skulls.161,173 TheSylvian sulci, the large folds along whichthe front part of the cut is made, also showleft-right asymmetry: the Sylvian sulcus islower, and the Broca's and adjacent areaslarger, on the left than the corresponding fea-tures on the right. Broca's and adjacent areasare associated with the fine control of speechvocalisation

input. Versatile brain development would thus havebeen favoured in a number of ways, with far reachingimplications for social interactions and genetic-memetic evolution. All this seems to fit into a selfconsistent picture of group dynamics and evolutionunder the extreme pressure to increase group size,with a high premium on intelligence and especiallysocial intelligence.

Jumping to more recent times we may note threelines of evidence, independent of the foregoing, allindicating that language was well developed by ahundred millennia ago at the latest. First, there arethe genetics and comparative linguistics of modernhumans across the globe, especially in culturallyisolated pockets, outside the major language groups,in places like Papua New Guinea. The implication isthat a language ability close to today's must havebeen fully formed by that time, if not earlier.167 Thefossil record, now beginning to include evidence fromDNA sequencing, suggests that the worldwide spread

RIGHT

CUT

occipitallobe

~ front tips of~ / frontal lobes

LEFT

temporal plane

rear poles ofoccipital lobes

possess new and decisive evidence on both. First,language is far more ancient than we used to think -specifically, far more ancient than the visual arts ofthe Upper Palaeolithic, more like hundreds than tensof millennia. Second, our prehistoric ancestors, orsome of them at least, had to survive still larger,more rapid, and more frequent climate fluctuationsthan we used to think. There was a highly unstableclimate regime throughout much of our ancestors'human and prehuman existence, suggesting morestrongly than ever that climate fluctuations wereimportant for our ancestors' development.

By prehuman existence I mean a fully bipedal, fullyground dwelling existence, which as far as the fossilrecord can tell us dates from around the beginningof the unstable climate regime, the Pleistocene,roughly 2000 millennia ago.173 It was probably thenthat the ability to abandon shrinking forests andmigrate freely began to compensate for greater expo-sure to predators. The record also shows, beginningnear that time, the first of two periods of strikinglyrapid brain expansion; see Fig. 1. This can be wellexplained in terms of the intensified selective pressurestoward ever larger group sizes that must, inevitably,have arisen at that time, from the exposure to pred-ators even if from no other cause (e.g. Refs. 166,173, and many references therein).

By human as distinct from prehuman existence Imean language speaking existence. Despite lingeringcontroversy it is now clear, from evidence to bereviewed shortly, that the human language abilityresides in genetic memory. This suggests in turn thatlanguage and brain are likely to have evolved togetherover a timespan sufficient for substantial geneticchange, probably hundreds of millennia at least. Thiswell explains the second period of rapid brain expan-sion, seen at the left of Fig. 1, what ChristopherWills161 has called the 'runaway brain' phenomenon.

The first period of brain expansion, from roughly2000 millennia ago, seems likely to have been associ-ated with a preadaptation for language, rather thanwith anything like language as we know it. Suchpreadaptation seems likely to have involved vocal aswell as visual (facial and gestural) communication -all highly advantageous under the pressure to increasegroup size, even if for no other purposes, at first,than social bonding and simple forms of signalling.Reference 173 makes a cogent palaeo anatomical casefor just such a preadaptation, pointing out first of allthat the characteristic brain asymmetries, illustratedin Fig. 2, were already present 2000 millennia ago,even though brain size was much smaller, suggestingan early trend toward elaborate vocalisation andauditory perception. Furthermore, the case continues,other anatomical features - including those relatedto bipedalism - have strong implications not only forvocalisation and hand-eye coordination but also fordiet and metabolism, and for infantile brain develop-ment. Bipedalism implies a small birth canal andearly birth, the more so as brain size increases, henceincreasingly early exposure of infants to a rich sensory

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of the human genome - the spread of our speciesfrom its likely original home in Africa - must havetaken a hundred millennia or more.

Second and third, the genetic basis of language hasbeen independently confirmed not only by increas-ingly clearcut psycholinguistic research resultsI76 butalso, very recently, by another piece of evidence thatis decisive in itself, concerning what linguists callcreolisation, or nativisation. This is the construction,from fragmentary raw material, of a syntacticallycomplete, syntactically consistent new language by asingle generation of children younger than 7 years orso - naturally and spontaneously, as part of theirrehearsal for 'real life', the deadly serious rehearsalthat we call juvenile play.177

A case of creolisation has now been observed anddocumented, in full detail, for the first time.167,178The story is fascinating and compelling. In Nicaragua,in 1979, there was a change of government thatbrought deaf children together in a new State schoolsystem, after long social isolation from other deafpeople. The result, within just a few years, was thecreation of two new sign languages the prior absenceof which is well documented: first a pidginlikesign language, syntactically feeble, inconsistent, andunstable, like other pidgins, and second a creole-likesign language, syntactically powerful, consistent, andstable, like other creoles, having the full range ofsyntactic or grammatical devices. The creole is nowdisplacing the pidgin. Close observation of the chil-dren's behaviour over a number of years, includingsystematic tests recorded on videotape, has estab-lished that the pidgin was created by children olderthan about 7 years, and the creole subsequently bythose younger. The only linguistic input to theyounger children was the fragmentary raw materialprovided by the older children's pidgin. There wasno way that there could have been any significantlinguistic input from adults.

Here then is the clearest possible demonstrationthat, astonishing as it may seem, genetic memorycontains, implicitly, the complete syntactic machineryof language. Or, more carefully stated, geneticmemory contains the complete wherewithal - theseeds of the self assembling, self organising, yet inputsensitive components - from which to build thatsyn tactic machinery.

Creolisation, remarkable though it is, need notsurprise an observant parent. English children whensmall tend to say 'I keeped mouses' before learningto say 'I kept mice'. As N oam Chomsky pointed outlong ago, it is not syntactic function and syntacticconsistency that young children have to learn fromthe language they hear or see around them. Rather,what they have to learn is the superficial form andabove all the irregularities of the language, the cul-turally evolved departures from syntactic consistency.As Steven PinkerI67 aptly puts it, 'a three-year-old ...is a grammatical genius'.

Now the language ability, like other functionalabilities of living organisms, must have developed in

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parallel with its most basic uses, as language becameever more critical to survival in increasingly largegroups or tribes. In the living world, functionalabilities develop through use, and only through use;and they atrophy through lack of use. Sooner orlater, the basic uses of language must have included,for instance, what we call storytelling - again partof, and growing from, juvenile play and again rehears-ing for real life, and doing so in more than one way- not only expanding the ability to imagine or remem-ber real situations that might be important to survival,such as, for instance, the climate and vegetation ofpast centuries,179 but also in the process developinglinguistic skill. Juvenile play in any species developsthe abilities and skills of that species. It is no accidentthat young children love stories - narratives if youprefer - and will create them spontaneously180 justas kittens propel small objects in order to chase them.N either thing needs to be taught, and both things areessential to the survival of the species.

Sooner or later, therefore, in our ancestors' evol-ution, linguistic skills must have become as importantas any other survival skill, hunting or gathering oranything else. In particular, as has often been sug-gested, linguistic skills must have been intimately partof what we call social skills: what grows not onlyfrom storytelling but also from making friends, allies,enemies, jokes, love - what grows from, what isdriven by, the imperatives of group survival andsocial cohesion. Social skills must have includedforms or precursors of what we now call rhetoric andadvocacy181 and the building, reinforcement, andexploitation of belief systems. Such skills would havebeen strongly selected for by the competition formates and for varieties of social influence within agroup or tribe; and that ongoing competition musthave been a continual and potent driving force forlinguistic evolution, genetic and memetic, a forceconspicuously at work today.167,182 So the skills wecall rhetoric and advocacy, in one form or another,must themselves have been survival skills and inti-mately part of the use and development of languageitself - notwithstanding our tendency to think ofrhetoric and advocacy as recent inventions, alongwith the associated cognitive symbolism.

Notice by the way that none of these uses oflanguage need have left the slightest archaeologicaltrace. The impermanence of sound waves, and ofvisual signals too, is sometimes forgotten in the heatof controversy. Furthermore, our powers of cognitivesymbolism - including the unconscious power ofabstraction discussed in Part II - are so intimatelybound up with unconscious levels of perception andcognition that they must have had origins far moreancient, even, than the timespan of Fig. 1.

This is one implication of the line of argumentdeveloped in Parts I and II. It is not only ourselves,but also monkeys and other creatures, that can avoida charging rhinoceros and therefore have unconsciousmodel fitting abilities. Language had no need to buildcognitive symbolism from scratch; it could develop,

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and make connections to, unconscious symbolicstructures already there.

The possibility thus suggested that the linguisticarts became highly developed long before therecorded visual arts, and that they were crucial totribal development, cohesion, memory,179 and beliefsystems166 provides an interesting variant of, oralternative to, pictures of cognitive development suchas that suggested in Ref. 183, which approaches theproblem from an archaeological perspective. Visualsymbolism recorded in art objects like beads andbracelets, first appearing in the Upper Palaeolithicarchaeological record a mere 40 to 60 millennia ago,could have been late developing precisely because thelinguistic or oral arts were already rich enough tosupport tribal cohesion and competitiveness. Theycould have been rich enough either on their own, or,more likely, complemented by unrecorded, butremembered, visual arts of mimicry and dance.

The early development of linguistic arts and skills,including storytelling, being presumably central tosurvival, would in any case have been intimately partof, and central to, the co-evolution of brain andlanguage - part of the whole biological point, or ifyou will, 'purpose', of that co-evolution under thecontinuing, and longstanding, selective pressures forcohesion and competitiveness, pressures that musthave been acute for at least half the timespan ofFig. 1, i.e. for more like thousands than tens ofmillennia. And the linguistic or oral arts, plus mimicryand dance, would have been among the most emi-nently portable art forms for a tribe on the move.

And tribal competitiveness must have involved, ofcourse, not just social cohesion, collective memory,improved hunting skills, and ways of coping withpredators, but also - inevitably - warmaking skills.174There must have been territorial warfare, includinggenocidal warfare, beginning on the small scaleobserved today among chimpanzees184but developingformidably as language and rhetoric developed,allowing tribes to expand yet cohere. And on top ofall the other selective pressures - putting a higherpremium on warmaking - would have been the forcedmigrations due to the unstable climate itself.

Such pressures must have been especially intenseduring the final hundred millennia or so, the finalspurt at the extreme left of Fig. 1, during whichmigration took many of our ancestors out of Africainto or through regions strongly affected by climateinstability. New palaeoclimatological evidence, atunprecedentedly sharp time resolutions, has revealedmany large and rapid fluctuations during that time.In some parts of the world at least, there were climatictemperature changes of the order of several degreescelsius 'within decades' .185There were large oscil-lations with periods of the order of 2 centuries.179And again and again there were large changes in sealevel, including episodes of sea level rise at rates upto about 3 metres per century. At such times andplaces the environmental change within an individ-ual's lifetime would have been far bigger, and swifter,

than the changes now being discussed in connectionwith possible manmade global warming.

Together with the vagaries of chaotic ecodynam-ics186 and human population growth, the climatefluctuations must have kept tribes on the move inwhat became a global scale diffusion, almost arandom walk in the technical sense of the term, inan unwritten saga of growth, famine, migration, andwarfare. As Ref. 173 reminds us - and equallycogently Refs. 161, 166, and 174 among others - therunaway brain evolution seen at the left of Fig. 1 isprobably the signature of, quite literally, an inten-sifying 'evolutionary arms race'.

The behavioural abilities and potentials that mostpowerfully coped with this situation - that producedthe largest, best coordinated, and most formidabletribes - must have been well established, and longestablished, in genetic memory by the time the climateturned warmer and more stable about ten millenniaago, leading to the first large agricultural communi-ties. Ten millennia is little more than an instant ofgenetic evolution. We may reasonably assume thatalong with formidable linguistic skills there must haveevolved our powerful sense of truth and falsehood,and an ability to accept as absolute truth the tribe'sbelief system, reinforced in times of need by the wordof a strong leader - giving leaders the power togalvanise followers into action while assuaging theirfear of the unknown.166,174As language is ancient,so is conviction politics. A tribe thus equipped wouldhave had overwhelming advantages over any thatwere not. The leaders' claim, implicit or explicit, tobe the mouthpiece of absolute truth would naturally,in times of war, have implicitly or explicitly portrayedany deviant beliefs, including a competing tribe'sbeliefs or alleged beliefs, as absolutely false and inneed of extermination. Numinous or visionary experi-ence, more probable in times of famine or otherhardship, would have served to reinforce such claims.And there can be little doubt, as already suggested,that we are genetically much the same now as tenmillennia ago.

Hypercredulity anddichotomisationFrom the evidence and the arguments just reviewed,it should be no surprise to find today, in geneticmemory, showing itself in many cultures, not only acapacity for such things as love, altruism, wit, invec-tive, poetry, rhetoric, and visionary experience -whose latency in genetic memory we can now demon-strate through mind altering drugs as well as throughthe natural mechanisms of stress and starvation - butalso a capacity, a tendency, an urge, a longing, aprofound need, stronger in some individuals than inothers, to believe in some unique Absolute Truth orAnswer to Everything, regardless of logical coherenceor supporting evidence.

There is a recognisable, indeed conspicuous, behav-iour pattern here,134,135on which I want to focus

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attention. It is a meme susceptibility if you will, abehavioural ability with a powerful and deep-rootedgenetic underpinning or genetic component. Weneed a name for it, if possible a neutral, non-confrontational, self explanatory name, a non-partisan name that helps dispassionate discussion andsteers clear of old feuds, cliches and distortions, thathelps us to grasp, to understand, something of whatis happening in today's world, and to understand thenew dangers we face. The best I can come up with is'hypercredulity', or 'hypercredulity instinct' .187Thebehaviour pattern in question seems to go beyondordinary credulity, gullibility or mental laziness, andbeyond the ordinary susceptibility to mental tunnel-ling or cognitive illusion.14o,188The likely importanceof such behaviour to our ancestors' survival explains,also, why human language and cognition are sostrong on feelings of truth and falsehood yet so weakon logical consistency checking - especially whencompared with, say, the relatively tight, but uncon-scious, consistency constraints on visual perceptiondiscussed in Parts I and II - why self contradictoryterms like 'heteroactive barber', meaning a barberwho shaves those and only those who do not shavethemselves, are not intuitively nonsensical eventhough actually nonsensical. 136

Bound up with all this seems to be the equallyconspicuous, and peculiarly powerful, human urge todichotomise or polarise, to make two way distinc-tions, to see things in black and white or as absolutelytrue or absolutely false, reflecting not only the 'we orthey' of tribal conflict but also the prelinguisticdichotomies like 'edible or inedible', 'fight or flight',and 'male or female', and tending to spill in otherdirections as well:

Don't equivocate! Either it's Nature or it's Nurture.Whaddaya mean, yes and no? Give me a straight answer.You can't have it both ways: either you're for God or

you're for Satan.Just tell us The Truth! Either X is safe or it isn't.

Aristotle's law of the logically excluded middle isreplaced by the urge to annihilate any kind of middle.Our politicians' exploitation of, or struggle against,such behaviour patterns can be seen every day. Evenwell educated, thoughtful, intelligent people who cansee that 'nature or nurture', for instance, is a falsedichotomy still tend to say, as I have observed oncountless occasions, that it's a matter of some percent-age of one and some percentage of the other.As geneticists are quick to point out now-adays,129,161,171,187that is complete nonsense - a bitlike talking about a lock and key mechanism that is300/0 lock and 700/0 key. No simple analogy cancapture the intricacy, complexity, and subtlety of thegenetic-memetic dynamic.

Here of course things get delicate, very close to thebone. If you will, I am using the words 'hypercredul-ity' and 'dichotomisation' as caricatures of a sort, asways of highlighting a particular aspect, you mightsay a primitive extreme, of our complex nature that

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needs to be recognised. I am not suggesting thateither word captures everything about the vast edificesof today's human belief systems, including what youmight fairly regard as their more civilised and spiri-tually necessary aspects. Indeed I want to draw asharp distinction between, on the one hand, hypercre-dulity understood in the sense of the primitive urgeto believe in a unique Absolute Truth and Answer toEverything - no alternative to which can be toleratedand no aspect questioned - and, on the other hand,the need for 'something to believe in' understood ina more democratic way, in the sense of a personaltruth or faith that may be shared with others butdoes not demand to be imposed on others.

This is a distinction that our ancestors could nothave been in any position to make. Throughout mostof prehistory, as we call it, a typical tribe would havehad to stick together or be wiped out. Indeed, asalready noted, the selective pressure to stick togethermust have been prelinguistic, and unremittinglyintense from the time that our ancestors becameground dwelling, bipedal, continuously exposed tolarge predators and also, probably, benefiting fromthe same predators through the leftover carcasses ofother large animals killed by them, supplying someof the high quality diet for expanding, metabolicallygreedy, energy hungry brains.173 Reference 166 sug-gests that aspects of what we call pagan religion andmythology - the obsession with blood rites, theworship of deities that are both fickle benefactorsand devouring monsters, the ecstasy of war andhuman sacrifice - could well have had their beginningsin those very circumstances, long, long before theexistence of language. So too, perhaps, does yetanother conspicuous and widespread human behav-iour pattern - the wordless, mindless urge to gamble,to tickle the monster's tail,189 to dare fate, to riskeverything for Victory, Power, and Glory.

The dark side of the PlatonicOne has to marvel at the extraordinary moment ofhistory we live in, and at our species' extraordinaryadaptability. It is a remarkable testament to thatadaptability, and to the power of cultural evolution,that any of us now dare make the distinction betweenhypercredulity and personal faith despite being gen-etically almost the same as ten millennia ago. Thedistinction is now understood and the making of itnow tolerated more widely, perhaps, than ever beforein human history and prehistory. 172Along with manyothers I would argue that a major reason for thisdegree of toleration, and for being able to make thedistinction at all, is respect - implicit or explicit,acknowledged or unacknowledged - for the scientificideal or its equivalent, for science not as absolutetruth but as rational, empirical, and sceptical think-ing: respect for taking experimental evidence seri-ously, and recognition that any claim to infallibleknowledge is, indeed, deeply irrational. The physi-cist Max Born put the point sharply but well: 'Ibelieve that ideas such as absolute certitude, absolute

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exactness, final truth, etc., are figments of the imagin-ation which should not be admissible in any field ofscience ... This loosening a/thinking [Born's emphasis]seems to me to be the greatest blessing which modernscience has given to us. For the belief in a single truthand in being the possessor thereof is the root causeof all evil in the world.'190 Jacob Bronowski, payinghis respects at Auschwitz, put the last point evenmore sharply: 'This is where people were turned intonumbers. Into this pond were flushed the ashes ofsome four million people. And that was not doneby gas. It was done by arrogance ... This is whatmen do when they aspire to the knowledge ofgods.'191

I am suggesting, then, that recognition of thedistinction between hypercredulity and personal faith,and social toleration of those making the distinction- which toleration always hangs, perilously, in thebalance - might once again gain ground if respectfor the scientific ideal were once again to gain ground.Such recognition, toleration, and respect are surelyfundamental to our chances of a civilised future; andit is precisely here - as I shall try to argue as cogentlyas I can - that there are implications for scientists'professional codes of conduct.

But recognition of the distinction means recog-nition, first of all, of hypercredulity itself. If, as isstill fashionable in some circles - and I have encoun-tered this even from scientific colleagues - if you areprepared to dismiss the sort of evidence I have citedand claim that it's all down to culture, a hundredpercent nurture without any nature, that there is nosuch thing as genetic-memetic evolution leading toinstinctive behaviour, that infant minds are blankslates and that tolerance is just a matter of a culturedeciding to be tolerant - whatever that might mean- then consider how to explain various observedphenomena.

Consider for instance the debate on the right todie. Consider indeed the observation that such adebate exists in, among other countries, the USA, ina culture born of escape from persecution and pro-fessing personal liberty as its highest ideal. Thisculture of personal liberty, declaimed throughout theanthem 'America' and in countless political slogans,seems unable to prevent the persecution, today, ofindividuals for holding to a personal faith thatdeclares no threat to others and is nothing but a sureknowledge of readiness to die at a chosen time, aloneor in chosen company, without harming others, andwith a felt sense of rightness or even sacredness. Theexample is noteworthy because 'sure knowledge', inthe sense of a personal truth or faith, has such anoutstandingly simple, clear, and testable meaning- manifested by willingness to press a switch that youknow will lead to your own death.

Such sureness, such personal faith, is not onlytestable; it has also been tested, in recent years,through the work of pioneers like Dr Jack Kevorkianof Detroit, Michigan, USA. At the cost of his ownmedical career, Kevorkian has made available to

ordinary people who consult him the means to dievoluntarily, peacefully, and with dignity, and at achosen time, alone or in chosen company, by pressinga switch - after due counselling, and with assurancesup to the last moment that a change of mind is noproblem. Kevorkian, though never himself pressingthe fatal switch, has been called a 'murderer'; and heand his patients have been subjected to legal andnewsmedia harassment, including police intrusion atthe family deathbed and actual murder charges,acquittal from which led to changes in the law priorto further attempts to convict.

These events, all on the record,192,193well illustratethe power of what I am calling hypercredulous belief,even when held by a small minority of the membersof a society. The individuals making the accusationsof murder with such prodigious assurance appear tobe driven by belief in a unique, infallible, and unques-tionable absolute truth, having the force of absoluteauthority over others even to the point of conferringthe power of life and death over them - the powerof death in the form of capital punishment,193 andthe power of life in the form of psychological orphysical torture: the compulsory prolongation ofgrossly humiliating indignity or intractable acutechronic pain, twenty-four hours of terrifying agonyeach day. The individuals seeking to exercise suchpower, citizens of the 'sweet land of liberty', as theanthem has it, would no doubt profess belief infreedom, democracy, and individual human rightsincluding the sanctity of life. Such doublethink, orhypocrisy as the case may be, is strong evidence -either way - for the existence of an immensely power-ful instinct, something having roots deep in geneticmemory and more powerful in some individuals, andin some circumstances or subcultures, than anybroader culture that weighs against it.

There is no lack of other examples. Considertoday's best known form of voluntary human sacri-fice.166Consider what it takes, if not hypercredulity,to become a kamikaze terrorist or suicide bomber -or martyr, depending on your viewpoint -literally, abringer of the 'divine wind' to save your people,certain of heavenly bliss for exercising, in anotherway, the power of life and death over others. Considerthe record on medieval witch hunting and its recentcounterpart in the Chinese Cultural Revolution.194Consider the power, and evident deep-rootedness,beyond reason, of ordinary, commonplace racismand sectarian hatred. 'People discover race hatred theway lovers discover love. It always seems utterly newand fresh to the hater ... And, like love, race hatredalways expresses itself in the same cliches, uttered asif the hater had discovered the principles of theuniverse.'195 Indeed, what thing in genetic memory,what Answer to Everything awaiting fresh discovery,could have been more powerful in winning the evol-utionary arms race suggested in Fig. 1, in galvanisingone tribe to exterminate another when the unstableclimate forced them together? We may yet learn tocall this thing the dark side of the Platonic.

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Again, consider the power of today's widely heldbelief, exploited by tycoons and flying in the face ofthe evidence, that Market Forces are the Answer toEverything - as distinct from the reasonable prop-osition that market forces are useful for somethings155,156,158though not for others.196 Considerthe related belief that Everything Must Be Measured,in dollars if possible, part of an 'audit culture' 197-200that brooks no questioning - as distinct from thereasonable proposition that measurement and audit-ing are useful for some things though not for others.Again, consider the power of the belief, among intelli-gent, highly educated people, that language dictatesthought - still, as far as I know, passionately held insome parts of the academic world of postmodernismand so called political correctness - the appealinglysimple idea that language is thought, that we aretotal and absolute slaves to our fickle and unstablesemantics (Korzybski-Sapir-Whorf hypothesis), asdistinct from the reasonable proposition that lan-guage, depending on how it is used, is a powerfultool for confusing or clarifying our thinking, and forinciting various kinds of behaviour, and that languagehas its more stable and its less stable aspects and itsdifferent timescales of evolution.167 Reference 135gives further telling examples.

And beyond those, consider finally, if you will bearwith me, the most straightforward, the plainest, sim-plest, and perhaps best documented example of all,that of the overtly fundamentalist religious cults thatexplicitly claim to have the Answer to Everythingand succeed, again and again, in recruiting teenagersand young adults not only from the depths ofThird World poverty and repression but also fromthe affluent heartlands of the economically privilegedWestern democracies; and consider the record ofpersonal testaments of those leaving the cults spon-taneously or through 'deprogramming' or its modernvariant, 'exit counselling' .201,202

Respect and humilityExit counselling is something that deserves widerpublic attention, along with other group exercises forloosening thinking.188 It is of interest not only toparents with sons and daughters in the fundamentalistcults, but also as illustrating Max Born's point - asa demonstration of how respect for the scientific idealcan loosen the grip of a pre-established hypercredul-ous belief. Exit counselling is non-coercive; and itdoes not talk about science as such, still less aboutflashing lights and bubbling beakers. Rather, it worksby skilfully stimulating the cult member's instinctiveinterest in coherence and self consistency, in whathangs together and makes sense, in what withstandsconsistency checking. It assumes, often successfully,that 'victims of cults are not characteristically lessintelligent than other people' .202Here is yet anotherillustration of our species' astonishing adaptability.It says again that respect for the scientific ideal, forcoherence, self consistency, and experimental evi-

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dence, for what hangs together, can strengthen andencourage such adaptability in a way that is likely tobe critical for our species' future.

Indeed, such respect is critical, I want to suggest,in a more ways than the mere loosening of thinking,the mere weakening of the forces that push us towardoverpopulation and tribal conflagration. There is apositive vision, a rational hope of alleviating ourspiritual malaise - of finding ways to rediscover thesacred without confusing it with the absolute203 -that can be put forward more persuasively than everbefore. Respect for the scientific ideal can increaseour chances of maintaining, and further developing,another kind of respect, born of growing understand-ing, and sheer wonder, a deeper respect for our ownnature as part of the biosphere and as living organ-isms whose subtlety, sophistication, and vast com-plexity makes our most powerful electronic computersand other machines look like the crudest of kindergar-ten toYS.204,205

We are beginning to learn such respect for whatwe used to call 'simple' organisms as well, such asbacteria. It is beginning to sink in that even a singlebacterium, a prokaryotic cell, even one whose com-plete DNA sequence is known, is far too complicatedto simulate in detail even on today's largest electroniccomputers - we can't even, in a computer simulation,fold all the proteins correctly yet, let alone accuratelyhypothesise how they function in their thermallyagitated environment ~ reminding us how implausibleis the idea that Computers are the Answer toEverything and that robots will soon, in every respect,outstrip not only bacteria but also the human brain,a single one of whose tens of billions of neurons is athousand or more times more massive, and orders ofmagnitude more complicated, than a single bac-terium.205 We are beginning to glimpse why suchcomplexity and massively parallel architecture arecrucial to human perception and cognition, whichmust deal with combinatorial largeness - and begin-ning to glimpse, as suggested in Parts I and II, wheremathematics, music, poetry, rhetoric, and the otherarts come from, and why rational and intuitivethought must, and do, work intimately together inmany more ways than we can be conscious of. Weare even beginning to learn, or relearn, what musthave come naturally to our ancestors: respect forecosystems and for the Earth as a whole. We arerediscovering that respect in new ways, through thewonderment of new insights, viewpoints, and vantagepoints inaccessible to our ancestors, through views oflarge and small worlds within worlds, through viewsof the cosmos, of quantum phenomena, of the bio-sphere, and of the Earth seen from space.

And respect for the scientific ideal, and the knowl-edge it has led to, have given us, for the first time inour existence, a rational hope of beginning to under-stand, of coming to terms with, of evolving moredemocratic ways of living with, our own instinctsincluding the need for 'something to believe in'. Suchunderstanding can add to the ways in which the

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energies unlocked by personal faith, courage, andenthusiasm can, and do, turn from destructive towardcreative uses, toward ways of spiritual health thataccept the naturalness, and the great value, of genetic-memetic diversity - of individual diversity and cul-tural diversity - ways that accept the different spiritualneeds of different individuals and groups of individ-uals, ways that make room for reverence but distancethemselves more and more surely from arrogance,bigotry, coercion, violence, and torture - from 'thebelief in a single truth and in being the possessorthereof'.

Quantum mechanics and theMind of GodCan such a vision, such a hope, be realised? Asalways, it hangs perilously in the balance. For thecultural evolution required will hardly be possiblewithout social stability and freedom of information.This means survival of democracy in some form.And, for the reasons already rehearsed, the survivalof any form of democracy must surely depend, amongother things, on respect for the scientific ideal orsomething equivalent - on the willingness to be opento rationality, to take rationality seriously eventhough rationality is not, cannot be, the answer toeverything. Echoing Born and Bronowski - andFriedrich von Spee, Thomas Ady, John Locke,Immanuel Kant, Karl Popper, Carl Sagan, MichaelWalzer, and many other careful thinkers down thecenturies,160,165,172,206I am arguing that, whateveranyone says about the evil of science or of scientists,a democracy that loses respect for the scientificideal or its equivalent will quite literally be in mortalperil.

For without the respect for evidence, for coherence,for logic, the willingness to think again and tore-examine the evidence - and without the willingnessto teach such things to our children151 - what canhold the line against hypercredulous behaviour,against primitive, raw tribalism in all its politicalpotency? What can stop torture or witch huntingwhen 'everyone knows' that exterminating witches isthe Answer to Everything?194For 'witches' read anycategory you like: for some people today, it is already'scientists'. Yet science is still our eyes and ears onan uncertain future.

Clearly, the peril is brought closer by the trend injournalism that treats science on an equal footingwith pseudoscience, with no attempt to look forinconsistencies.207 Clearly it is brought closer by thecommercial and political moves against the freeexchange of data and against scientific independencegenerally, to be discussed below. But the peril is alsobrought closer - for reasons I hope my discussionhas made obvious - whenever a scientist is perceivedas claiming to be the mouthpiece of absolute truth,or as suggesting that science might lead us to absolutetruth or that scientists view science as the answer to

everything or as a way to know the Mind of GOd.134Whether or not a vague metaphor is intended, and

whether or not such metaphors can be the privateinspiration of great scientific achievement, is besidethe point here. What is at stake is public perceptionand its mind sets, and the survival, or not, of publicrespect for the scientific ideal and the survival ofdemocracy itself. I say this with the most profoundpersonal respect for some of our greatest scientists,such as Albert Einstein, who quite innocently usedthe 'Mind of God' metaphor or something like it.One feels that Einstein got away with it because heshowed respect and humility.

I think most scientists recognise the problem andtry to be careful about it, most of the time. However,it seems that we as scientists, or enthusiasts forscience, are not always careful enough, especiallywhen under political and newsmedia pressure andwhen tempted to use words like 'truth', 'certainty',and 'heresy' in the heat of debate. Once again wehave a false dichotomy, and a supremely dangerousone: Science as Mere Opinion208,209versus Science asAbsolute Truth, or Religious Belief.134

Take for instance some of today's pronouncements,and tacit assumptions, about quantum mechanics.They are strikingly similar to the pronouncementsand tacit assumptions about classical physics in thelate nineteenth century, which seemed to take forgranted the absolute truth of a particular set ofbeautiful, high precision model building blocks, theprinciples of classical physics.15o,210Just as thosenineteenth century pronouncements ignored orplayed down known inconsistencies, like the electronspiral catastrophe in blackbody radiation, so do someof today's pronouncements seem to ignore or playdown what may prove to be inconsistencies between,for instance, quantum theory and gravitation theoryat the Planck scale211of about 10 - 33cm and, moreimportant still, seem to ignore or play down knownpoints of inconsistency and vagueness in the quantummechanical principles themselves, which have beenwell aired in the literature and to which I shall refershortly. Indeed there seems to be a largely unspokenbelief in the absolute truth, and completeness, ofpresently known quantum principles, or even of thesubset of those principles presently expressible inprecise mathematical form, describing what is calledthe unitary or Hamiltonian evolution of wave-functions or state vectors. Related to that subset,though not in a fully consistent way212,213- and seethe references to 'branching rates' below - is thehypothesis of many worlds or many universes. Thissays that 'all possible worlds are actual worlds', 212inthe sense that there are as many universes as thereare quantum possibilities, a combinatorially largenumber to beat all combinatorially large numbers. Ivividly remember hearing, around 1995, a well knownphysicist, someone who has done significant researchin quantum theory and whose work I personallyadmire in many ways, saying clearly and forcefullyin a television documentary that the many worlds

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hypothesis describes a reality about which we can beabsolutely certain.

Such prodigious assurance can hardly be rational.I dare to hypothesise that it may instead be deeplyinstinctive - in a word, hypercredulous. It is to becontrasted with the more careful available discussionsof quantum mechanical technicalities, which latterare fundamentally simple, mathematically speaking,even if their meaning is dizzyingly strange and themathematical spaces dizzyingly and unimaginablylarge.149,150,21Q-221The many worlds hypothesis is notonly untested, and arguably untestable in its presentform, but also seems oblivious to the basis of scienceitself, including Occam's razor. All the well tested,accurate, reliable, hardcore scientific knowledge wepossess - indeed, the very ideas of 'knowledge','reliability', and 'testing' - have been based, so far,on the hypothesis that we and our fellow creatureslive in a single world, what I have been calling 'the'outside world, also 'reality', 'physical reality', 'physico-chemico-biological reality', or what you will, a singleworld in which the same things and events can beobserved by different people and the same experi-ments repeated by different people.222 Although thesingle world hypothesis, like everything else, is notabsolutely provable - and might somehow be shownone day to be untenable - it has withstood far moreconsistency checking than any other scientific model-making assumption. The single world hypothesis hasgreat simplifying power. It is arguably the most basicand powerful way in which we use Occam's razor,consciously as well as unconsciously. Abandoning itwould call for very hard evidence indeed: far morethan speculative hypotheses, supported by no experi-mental tests, about quantum mechanics outside itspresently established domain of applicability.

Having dared to stick my neck into a controversythat is - oh sacrilege! - not even within my ownresearch speciality, I must now return briefly to thetopic of free will discussed in Part II. Why? Becauseour subjective experience of free will has been claimed,in a remarkable and interesting book just pub-lished,147 to be decisive experimental evidence infavour of the many worlds hypothesis - in the strongsense that all explanations of, or discussions of, freewill within any single-world framework are 'puregibberish' (p. 339 of Ref. 147). My reply to thisdepends on the arguments given in Part II. In brief,the claim just referred to is on the same footing asthe claim, dealt with in Part II, that acausalityillusions force the abandonment of ordinary physicalcausality principles. The point is that both claimsignore what is known, and easily checkable, aboutthe workings of perception and cognition.

As was explained Part II, there is no need to regardfree will as an illusion. Free will is a percept. It is nomore and no less illusory than other percepts, likethe perceived time of striking a piano key, or ofhitting a fast moving ball. Such perceived times canbe accurate to within milliseconds and anything butillusory, especially if you use them to become a great

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pianist or the Wimbledon Champion. All I am saying,and this is the point missed in Ref. 147 and in someother discussions of free will, is that subjective experi-ences are - can be none other than - properties ofthe brain's internal models or, in the language ofRef. 147 itself, properties of the brain's own 'virtualreality' apparatus, whose inputs include sensory data.Included in those internal model properties are thesubjective experiences or qualia that we call the flowof time and the sequence of events, and equally thesubjective experiences we call consciousness, free will,intentionality, planning, and action. The multiplepossibilities of planned and intended actions canreside wholly within the brain's 'virtual reality'apparatus, and have no need of actual physicalcounterparts within a still vaster multiplicity of worldsor universes.

Let us return to the main point. Many worldshypotheses or not, there seems to be a whole mystiquebuilt on assuming that the quantum principles, asused today, are the complete, final, absolute, andunquestionable truth, with an unquestionably un-limited domain of applicability. That mystique issometimes associated with the term 'quantum philos-ophy'.215 The moment you ask what the principlesare, you find that besides unitary evolution theyinclude extremely vague notions of 'measurement'and 'observer', or of mysterious 'branching rates' orsomething equivalent. 217If you dare to point this out- that the lack of a clear, self consistent definition ofan essential and fundamental element shows thatsomething important must be missing from the theory- then you might be told that you are not evenallowed to try to make the theory more nearly com-plete. It is taboo; it is not to be questioned. You mustnot dare to define such an essential, inscrutableelement, because, as some might tell you, it defies thevery rules of logic, or has its own arcane rules of'quantum logic'.215Or you might be told almost theopposite, that the thing is forbidden because vonNeumann's anti-hidden-variable theorem forbids it.This is what has been called the 'unspeakable' partof quantum mechanics.146

Why 'almost the opposite'? Von Neumann'stheorem - or any other mathematical theorem - usesordinary mathematics, and therefore ordinary logic,as distinct from 'quantum logic'. You do not needany expertise, therefore, to know that the theoremcan have no bearing on something undefined andinscrutable. Mathematics is a sophisticated kind ofconsistency check. It tells you what follows fromcertain assumptions stated precisely. Wonderful andawesome though mathematics can be, it does notdeal with the vague, the inscrutable, the ineffable.The points just made, including the irrelevance ofvon Neumann's theorem, have been cogently arguedin Refs. 146 and 218 and elsewhere; see also Note 212.In many worlds and related theories, including thosecarrying the label 'decoherent histories' or 'consistenthistories',221 the vagueness arises in connection with,the branching rates already mentioned. They are also

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400

300

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Frequency (cm-')15 20

3 The astonishingly close fit between the radiation law or Planck function for blackbody radiation attemperature 2'728 0004 K (thin curve) and recent measurements of the mean cosmic backgroundmicrowave radiation. The measured points and their statistical error bars are invisible. They are smallerthan the thickness of the plotted curve. From Ref. 223; q.V. for full technical detail (to convert the valuesat left from megajansky per steradian to 51 units, W m -2 (m -1)-1 sr-1, multiply the values by2'99792458 x 10-12)

called proliferation, splitting, or divergence rates;l47and though talked about, or written about, they arenot specified quantitatively.

Respect for the success of standard quantum mech-anics compels us to say that in some sense, whichno-one fully understands - a point on which expertsagree - it is a superbly good model. It is an astonish-ingly accurate and reliable model, of certain aspectsof the outside world in an impressive range of circum-stances. Among many examples, one of the simplestyet most striking - especially when regarded as evi-dence for a vast domain of applicability - is the socalled blackbody radiation law, the curve plotted inFig. 3, and, by implication, its quantum mechanicalbasis. The radiation law closely fits not only therelevant laboratory data but also very precise obser-vations of what is called the cosmic backgroundmicrowave radiation, consistent with cosmologicalmodels in which the radiation fills the whole universeand originated, in a thermodynamically reasonableway, at an early stage of the cosmic 'big bang' .224Reference 223 gives the technical details concerningobservational accuracy; note, however, that in Fig. 3not only the observational points, but also theirstatistical error bars, are invisible - hidden entirelyinside the curve.

Standard quantum mechanics correctly predicts,furthermore, phenomena so strongly counterintuitivethat their repeated experimental confirmation is oneof the greatest wonders of the world. The fact thatcomputers work, most of the time, is wonder enough;and there are phenomena still more conspicuously

strange, going under names like entanglement,quantum teleportation, or Einstein-Podolsky-Rosen-Bohm phenomena, now confirmed by many carefulexperiments. 149,212,216

But respect for the scientific ideal says that, despiteall this, we cannot accept any taboo on changes tothe quantum principles if goodness of fit is preserved,as it can be in, literally, countless ways - a combin-atorial infinity of ways. Most of these are frivolousin the sense of grossly violating Occam's razor,but there now exist a number of serious pro-posals, to change or add to quantum principles, infairly simple ways that extend domains of applica-bility and define them more precisely, without aban-doning the single world hypothesis, without relyingon vague ideas about 'measurements', 'observers','branching rates', or their equivalent, withoutviolating self consistency, and without affecting thegoodness of fit to experimental data obtained sofar.146,220,225,226These are what the late John Bellcalled 'sharp quantum theories' .212

What I have been trying to say about humaninstincts and behavioural tendencies and about per-ception and cognition, and about our unconsciousdrive to prune combinatorial trees of possibilities,136arguably throws some light on why sharp quantumtheories have tended to be ignored, even though theearliest such theory was developed by famous physi-cists and has been around for a good many dec-ades.212,215,219I would argue that this is enough initself to tell us, for one thing, that we must be nearerthe beginning than the end134of science.

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Scientists in publicThe preceding sections try to bring into clearer viewsome of the psychological forces working against thepublic understanding of science, and against publicrespect for the scientific ideal. But before goingfurther, I hope we can take stock and agree on foursimple points that have already been touched on invarious ways. They are hardly new, though oftenforgotten; and the first three at least must surely beobvious to anyone who considers them, even for amoment, regardless of specialist knowledge about thePlanck scale or electrons or brain function or any-thing else. They must surely be obvious - glaringlyobvious - to, in particular, sceptical and thoughtfulnon-scientists:(i) all our knowledge of things outside us depends,

directly or indirectly, on perception as well ason conscious reasoning

(ii) perception in the everyday sense is limited,approximate, and fallible, though astonishinglyaccurate and reliable in some range of circum-stances (as when avoiding a highway collision,landing an aircraft, or recognising a familiartune or a friend's voice)

(iii) scientific knowledge is also limited, approximate,and fallible, though astonishingly accurate andreliable in some, often much greater, range ofcircumstances (as when navigating to Jupiter,cloning antibodies, or building a computer thatworks)

(iv) both everyday, unaided perception and the exten-sion of it we call science depend - inescapablyand fundamentally - on modelling assumptions,some of them wholly unconscious. A dependenceon such assumptions is inescapable because thenumber of possibilities to be coped with is alwayscombinatorially large.

The fourth point, argued for in Parts I and II, impliesthat what has just been said is less superficial than itmight sound. On the contrary, it is about as funda-mental as you can get; and it is consistent withexperience. In particular, as recalled earlier, scientificadvances have often depended on exposing uncon-scious modelling assumptions.

The view summarised by the four points is not,incidentally, to be confused with the 'positivist' or'instrumentalist' view of science put forward in philo-sophical debates such as that on 'realism versuspositivism' (see Part II, also Refs. 227-230 below).Those debates, like the debate on whether science is'objective or theory laden', all seem to stem from thefalse dichotomy that science is either about dis-covering reality or about fitting models, as if youcould have the one thing without the other.

Points (i)-(iv) try to incorporate and reconcilewhat seems valid on both sides of the dichotomy. Ithardly needs adding that, for given accuracy, somemodels are better than others in the sense that theyseem more natural, and convey better or deeperinsight or understanding. The best models in this

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sense satisfy, almost by definition, a strong form ofOccam's razor: they have properties of lucidity,beauty, and simplicity that help to make them access-ible to our intuitions. 147-150If such a model accuratelyfits some aspect of reality, then it makes that aspectcomprehensible. One might say that the consciousand unconscious aspects of such models are wellintegrated, and mutually consistent.

Now it is easy to lose sight of point (iv), inparticular, when contemplating the power, the scope,and the accuracy of hardcore scientific knowledge -the sheer hardness of hardcore scientific knowledge.If a model of a protein molecule composed of ahundred thousand model atoms linked in a definiteway, and subject to thermal agitation in a certaintemperature range, behaves as a miniature precisionmachine231 or as an elaborately constructed yetreliable logic gate174- and in such a way as to fitdata from many careful experiments - then we areimpressed and awed, just as we are by cases likeFig. 3, by the goodness of fit between high precisiondata and the great theories, the great models, ofphysics, the more so when we contemplate their stillmore awesome simplicity, beauty, and economy150and their power, or potential power, to convey under-standing. 147The chance of such goodness of fit occur-ring by accident is combinatorially small, like thechance of opening a large combination lock at firstguess.

Knowing about the huge effort that went intodiscovering and repeatedly checking these astonish-ingly accurate and reliable models, and faced withthe far greater uncertainties at the research frontiers,scientists are understandably impatient, not to sayangry, with suggestions - and school curriculumproposals - saying that the validity of such models ismerely a matter of opinion or cultural bias.232 Toanyone who knows anything about science this is likesaying that cultural bias dictates the validity ofnormal visual perception, in broad daylight, of alarge and brightly painted juggernaut truck approach-ing head-on collision with your car, or that culturalbias dictates what happens when you step out of atenth storey window. In some cases the repeatedgoodness of fit, and the variety of crosschecks fromdifferent viewpoints, is such that we can talk aboutpractical certainty - about a probability still closerthan unity than the probability of being dead afterimpact, a probability so close to unity that it iscomparable, say, to the probability (and culture inde-pendence) of tomorrow's sunrise, or of green pencilsnot falling upward.

It is considerations like these that underlie theworking scientist's shorthand terms 'proof', 'hardfact', 'decisive evidence', 'law', 'certainty', 'truth','true theory', 'good understanding', 'established fact',and so on. As normally used by scientists147,224theseterms signal that attention is being directed elsewhere,away from practical certainties and near certainties,as presently judged by people who have looked atthem seriously, and toward the fog of uncertainties

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that the scientific research is trying to penetrate. Adetective trying to solve a murder mystery is notinterested in lengthy discussions of whether gunsthrown into rivers fall upwards or downwards, unlessexceedingly good evidence for their falling upwardsis unexpectedly found.

But we still have a problem, indeed a crisis. Deepin our nature, latent in genetic memory, stronger insome individuals than in others, lurks what I calledthe hypercredulity instinct. The word hypercredulitymay be a caricature, but I hope to have convincedyou that what it caricatures is something so powerfuland dangerous that scientists, and democratic humansocieties, can no longer afford to ignore or underesti-mate it (as did the US State Department overBosnia163). If I have not yet convinced you, thentake a look at Refs. 134 and 135, or simply imagineyourself caught up in circumstances the like of whichyou may never have experienced, between a .risingsea and a strange tribe that wants what's left of yourterritory and can't even speak English. Or see if youcan explain in another way why human language andcognition are so strong on feelings of truth andfalsehood yet so weak, as noted earlier, on logicalconsistency checking.

Words like 'truth' are indeed emotionally loaded,and liable to be misunderstood, by ourselves as wellas by others, in a profoundly dangerous way. This isthe case even when political temperatures are nothigh, even when there is no official secrecy, nodeliberate camouflage and deception of any kind, nolegal or commercial pressures. There have been incess-ant reminders of the problem. The evidence I havereviewed - including the evidence from creolisation,with its implications for the nature and origins oflanguage and cognition - shows that the problem isdeep-rooted in genetic memory - more strongly, nodoubt, in some individuals than others. So we arestuck with the problem, genetic engineering fantasiesnotwithstanding. 162

For those of us who are professional scientists, theimplication is clear. If we want to help to buildrespect for the scientific ideal, then we shall have tokeep looking for more and better ways to remindboth ourselves and the public, as many scientists doalready, that claiming practical certainty (and cultureindependence) is different in principle from claiming,or seeming to claim, absolute, final, and infalliblecertainty or even the possibility of such certainty,that being awed and impressed by Fig. 3 or beingconvinced that a big breakthrough in theoreticalphysics is in prospect150 is different in principle -profoundly, fundamentally, and crucially different -from claiming, or seeming to claim, that any scientifictheory is, or could ever be known to be, exact andabsolutely true with the whole universe for all time,and everything in it, as its domain of applicability.

Here, once again, things get delicate. We canreasonably, if perilously, talk about scientific truth ifwe somehow make clear that it means, as with pencilsfalling, practical but not absolute certainty.224 We

can reasonably, if perilously, talk about a search fortruth, in the sense of trying to break through, oftrying to make decisive advances in the scope, accu-racy, simplicity, and insightfulness of our knowledge,if we somehow retain, in addition, a certain humility:a humility that respects the complexity of things andsays that we cannot expect to be infallible oromniscient - that we cannot expect science, or anyother human activity, to be the absolute and certainAnswer to Everything, to be the Way to an attainableand knowable absolute, final, and infallible Truth, toa knowledge of the Mind of God. To think that finiteevidence can give infinite knowledge - despite thecombinatorially large tree of possibilities and ourunconscious drive to prune it233- is not only, selfevidently, a cognitive illusion but arguably our mostdangerous cognitive illusion. The poet Hilaire Bellocseems to have sensed this danger when he wrote, inan extraordinary sonnet first published in 1938, asthe darkness spread over Europe, the lines234

Believing Truth is staring at the sunWhich but destroys the power that could perceive.

The biological, climatological, linguistic, palaeo-anthropological, and perceptual-cognitive evidencesays the same thing. So does the evidence fromBosnia, from Cambodia, from the Middle East,from Northern Ireland, from Rwanda and Zaire, andfrom Auschwitz, the obscenity of 'what men do whenthey aspire to the knowledge of gods'.

So I am arguing that the foregoing is the veryopposite of hair splitting, and that it is relevant toscientists' professional codes of conduct and to thecrises in science policy and public understanding andto the threatened crisis in democracy itself. If helpingto build a stable, civilised society is among ouraspirations, if we want human societies to evolveaway from primitive behaviour, then those of us whoare professional scientists might want to considerwhether professional codes of conduct should beindifferent to a scientist's publicly claiming, or seem-ing to claim, that science can lead us to absolutetruth. We might want to consider whether to regardsuch claims not only as unprofessional, but more tothe point recklessly irresponsible, and incalculablyperilous, endangering not only science itself but alsohumankind - like playing with matches in an explos-ives factory, playing with the 'combustible mixtureof ignorance and power' now threatening to 'blowup in our faces' .135We might even want to considerwhether professional codes should not explicitlyrespect a principle of humility or, if you will, 'epis-temological uncertainty', acknowledging publiclywhat most scientists would concur with privately,that claims to the absolute, infallible, and knowablyfinal truth of any present or future scientific theorycannot possibly - for anyone who respects the scien-tific ideal- have any basis beyond instinctive feeling.We might, in addition, want to remember that makingsuch claims or seeming to do so - tempting thoughit may be under pressure from journalists, publishers,

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politicians, funding agencies, and our instinctivefeelings - plays straight into the hands of those ofour fellow humans who want to see scientists as justanother category of warring tribes, with their ownarbitrary belief systems and their tribal leaders claim-ing to be the mouthpiece of absolute truth. It is noaccident that the conflicts thus arising are now called'science wars'. 235,236

So what is distinctive aboutscience?Have we gained any insight, then, into the 'scepticalquestions asked by thoughtful and intelligent non-scientists' and into how to answer them effectively?Wearing my optimist's hat, I dare to hope that wemay have. Suppose we accept, as I think most scien-tists do already, that both ordinary perception andscience work by fitting finite, self consistent modelsto finite amounts of data, and that these are indeedmodels and not absolute truths. Then we immediatelyhave a coherent and simply explicable view of science,well supported by evidence like that described inPart II and easily understood by intelligent lay people.We can then speak accurately of 'science as anextension of ordinary perception', or 'science as oureyes and ears on an uncertain future'; and we canalso - then - give clear, dispassionate, uninflatedanswers to the sceptical questions asked by thoughtfuland intelligent non-scientists.

What, if anything, they ask, is objective and cultureindependent about science? What, if anything, makesscience different from other belief systems? What, ifanything, makes it different from fundamentalistreligion? Doesn't the non-uniqueness, the 'incommen-surability' of scientific theories discussed by Kuhn,Feyerabend, and others show that scientific theoriesand beliefs are arbitrary products of culture andtribal allegiance, whose seeming objectivity is yetanother illusion?

We can answer very simply. What is distinctiveabout science is the scientific ideal. What is distinctive,and crosscultural, about the ideal is its closeness tothe genetic foundations of perception - part of thegenetic inheritance shared by all tribes and culturestoday, an inheritance across unimaginable timespans,from many, many thousands of millennia of evol-ution. That inheritance provides us with the auto-matic, unconscious model fitting abilities that makepossible the unconscious 'science in miniature' we alldevelop from infancy, and use to build coherent, selfconsistent internal models of, and thereby becomevividly aware of, the earth under our feet and thetrees, mountains, ocean waves, wildlife, and peoplearound us. These are model fitting abilities that workapproximately and imperfectly, yet whose power andefficiency, far outstripping that of any artificial