Philosophy http://journals.cambridge.org/PHI Additional services for Philosophy: Email alerts: Click here Subscriptions: Click here Commercial reprints: Click here Terms of use : Click here Who's Afraid of Determinism? Leslie Stevenson Philosophy / Volume 89 / Issue 03 / July 2014, pp 431 - 450 DOI: 10.1017/S0031819113000867, Published online: 10 January 2014 Link to this article: http://journals.cambridge.org/abstract_S0031819113000867 How to cite this article: Leslie Stevenson (2014). Who's Afraid of Determinism? . Philosophy, 89, pp 431-450 doi:10.1017/S0031819113000867 Request Permissions : Click here Downloaded from http://journals.cambridge.org/PHI, IP address: 138.251.162.251 on 16 Sep 2014 Who’s Afraid of Determinism? LESLIE STEVENSON Abstract Becauseoftheidealizationsinvolvedintheideasofatotalstateoftheworldandofall thelawsofnature,thethesisofall-encompassingdeterminismisunverifiable.Our everyday non-scientific talk of causation does not imply determinism; nor is it neededfortheKantianargumentforageneralcausalframeworkasaconditionfor experience of an objective world. Determinism is at best a regulative ideal for science,somethingtobeapproachedbutneverreached. 1. The status of determinism Determinism is standardly understood as the thesis that the laws of nature together with the state of the world at any particular time necessitate the state of the world that must come next. Since the same applies to every future instant, the whole subsequent history of the universe would be predetermined. In the early nineteenth centurytheFrenchmathematicianLaplaceexpressedthismetaphys- ical claim in epistemological form: if a super-intelligence or demon knew the total state of the universe at a given time and all the laws of nature, then the demon (or these days, a super-computer) could dothecalculationsandpredicteverystateoftheworldwithmathemat- icalcertainty.(Legend hasitthatwhenthe EmperorNapoleon asked him where God came in, Laplace replied ‘Sire, I have no need of that hypothesis’.) Indeterminism is the negation of determinism – that there is at least one case in which the future is not necessitated by thepresent. Over the last few centuries it has seemed to many people intellec- tuallycompulsorytobelieveindeterminism,inlightoftheimpressive progress of science and our continuing commitment to scientific method. Admittedly, the advent of quantum mechanics has shaken belief in universal determinism at all levels of nature, but the theory of chance events at the sub-atomic level has not done much to stop a widespread fear that determinism may still apply at the level of human behaviour. Yet the possibility cannot be ignored that random micro-events may result in some degree of indeterminism at the macro-level, as illustrated by the notorious thought-experiment doi:10.1017/S0031819113000867 ©TheRoyalInstituteofPhilosophy,2014 Firstpublishedonline10January2014 Philosophy 89 2014 431 Leslie Stevenson of Schrödinger’s cat, and (so I am told) by recent developments in quantum computing and cryptography. And there is a long- standing argument that even if there should be some indeterminism inthebrain,thatwouldnotamounttofreewill,whichsurelyinvolves someconnection(whichneednothoweverbedetermination)betweena person’s decisions and the reasons for them in her thoughts, desires and feelings. A ‘choice’ that is determined by a sub-atomic chance event hardly seems like a choice at all. Indeterminism might be a necessarycondition of freewill (though that haslong been denied by compatibilists), but it is certainly not a sufficient condition. Thus philosophers have continued to debate the implications for free will if determinism is true, and to exercise their conceptual ingenuity on avarietyofsubtlepositionsaboutthecompatibilityorincompatibility of free will with determinism. This debate is predicated on a wide- spread assumption that determinism is a coherently-statable, extre- mely general, yet ultimately empirical claim about the overall character of our universe – and that science has provided strong evi- denceforitstruthatanylevelabovethe atomic. However I am going to argue that there are several fundamental difficulties in this apparently easily-stated but ambitiously world- encompassing conception. Even before we get to physical science, there is a purely mathematical obstacle in the way of a Laplacean demon or computer. Most of us, knowing little science (perhaps only the school textbook statements of Newton’s laws of motion) tend to assume that the calculations can be straightforwardly per- formed.Butthatistobetrayignoranceofthecomplexityofthemath- ematicsthatisinvolved.Eveninthelong-standing paradigm caseof gravitation, whose mathematics is elementary by today’s standards, thereliesaproblem.Newton’sSecondLawofMotionsaysthataccel- erationofabody,i.e.thedoublederivativeofdistancewithrespectto time,isequaltotheforceactingonitdividedbyitsmass.Sotoknow itsvelocityatanytimewehavetointegratethedifferentialequation; and to predict its position we have to integrate again. If there were only two bodies in the universe, then given their masses and their relative distance we can readily calculate the gravitational force acting between them and thustheiracceleration towards each other, and hence their velocities and positions at subsequent times after their initial positions and motions. If however we imagine three masses isolated from all other forces, the derivation of predictions about their relative motions and positions poses the classic ‘three body problem’ that is apparently still unsolved in principle, though there are methods of making approximate predictions for practical purposes (so that we were able to send men to the moon and back). 432 Who’s Afraid of Determinism? Themoralofthestoryisthateveninthatverysimpleartificiallyiso- latedcase,althoughwebelievethatthefuturestatesofthesystemare completely determined by the laws and its initial state, neither our best mathematicians nor our most powerful computers can derive predictions with absolute precision. Recent developments in the mathematics of so-called ‘chaotic’ or nonlinear systems show that for some equationsthe predictions that canbecomputedfrominitialstatescanvarydramatically,depending onverysmalldifferencesintheinitialstates(asinthe‘butterfly-wing effect’ontheweatherontheothersideoftheworld).‘Chaotic’isnot really the best label for these systems, for the output values remain mathematically determined by the input values, it is just that tiny differences in the inputs can make huge differences to the outputs. Thismeansthatinpractice,giventhatallofouractualmeasurements have limits of accuracy, some of our predictions are liable to large errors for complex systems such as the worldwide weather, and that most complex system in the universe, the human brain. But the point is also instantiated in simpler systems that we use to generate ‘random’ outcomes, such as tossing a coin, or dropping a ball to bounce downthrough anarrayofpins,orthemoreelaboraterando- mizingdevicesnowusedinnationallotteries;inthesecases,ahuman actionstartsaphysicalprocesswhoseresultcannotbepredicted.Itis not just that we lack the technology to make sufficiently precise measurements of the relevant variables, those systems are designed to have so much multiplication of tiny differences that no measure- ment could ever make realistic predictions of outcomes. We here get indeterminateness arising from the limits of measurement, even where Newtonian mechanics is assumed to apply.1 ThatisthefirstdifficultyintheLaplaceanpicture.NextIwantto pointouthowmuchidealizationisinvolvedinthenotionofthetotal stateoftheuniverseatanyonetime.Thereisnoprospectofanyone(or anycomputer)everknowingsuchatotalstateofthisworld,including thesizeandshapeandfallofeveryleaf,themotionofeverymolecule intheair,theexactmixingofgenesineveryactofreproduction,the firing of every neurone in animal and human brains – let alonewhat happens on other planets and in the nuclear innards of billions of 1 AsElizabethAnscombenotedinherinaugurallecture‘Causalityand Determination’(Cambridge:CambridgeUniversityPress,1971),reprinted in E. Sosa (ed.) Causality and Conditionals (Oxford: Oxford University Press,1975).Thepointhasalsobeenmadebythedistinguishedmathema- tician Roger Penrose, in The Emperor’s New Mind (Oxford: Oxford UniversityPress,1989),224–5,559. 433 Leslie Stevenson stars.Somephilosophers arenotimpressedbymereepistemological difficulty however, and will insist that this does not disprove the metaphysical thesis that there exists a total state of the universe at each moment.2 Peter van Inwagen has provided one of the most careful formu- lations of metaphysical determinism.3 He expresses it in terms of propositions, which makes it sound language-relative, but prop- ositions as he defines them correspond to ‘possible ways the word could be’, and those ‘ways’ can outrun what can be expressed in any particular natural language. Thus his definition of determinism hasasitsfirstclause:‘Foreveryinstantoftime,thereisaproposition thatexpressesthestateoftheworldatthatinstant’.Somephilosophi- calhearts(includingmine)willquailatthethoughtofamonstrously large proposition that expresses every instantaneous detail of the entire universe, but metaphysicians are made of stronger stuff and remain confident that their armchair formulations can encompass thewhole of reality. It does not help if we try to think an enormous (perhapsinfinite)numberofpropositions,eachofwhichcorresponds to a way that some determinate part of the world can be; for the conjunction of any set of propositions is itself a proposition, so if youarepreparedtorecognizesomesuchcompletesetofsmallerprop- ositions,youcangettheOnegreatWorld-encompassingProposition for free. The underlying intuition is robustly, indeed extremely, Realist: namely, that at any time there is such a thing – or fact, or state of affairs, or truth – as the way the whole world is, including everydetailofeverything.AndtheMetaphysicalorOntologicaldefi- nition of determinism is that, given the Laws of Nature, each com- plete instantaneous state of the world determines the state of the world at anyother time (orat least, at any future time).4 HoweverIamgoingtoarguethatuniversaldeterminismisnotan empirical thesis at all, but ratheran idea or ideal in Kant’s sense. In support, I cite Nancy Cartwright (who knows vastly more science and philosophy of science than I ever will) who describes universal 2 SeeJohnEarman,APrimerofDeterminism(Dordrecht:Reidel,1986), II.3–4. 3 PetervanInwagen,AnEssayonFreeWill(Oxford:OxfordUniversity Press, 1983) Ch.3, reprinted in Free Will, 2nd edition, ed. Gary Watson (Oxford:OxfordUniversityPress,2003). 4 At first sight it seems possible that the same total world-state could come about from two different preceding states – but I do not need to decide that question here. Earman offers an equivalent definition in terms of time-slices of all physically possible worlds, i.e. possible worlds that satisfythelawsofnaturethatholdinouractualworld,op.cit.note2,II.6. 434 Who’s Afraid of Determinism? determinismasa‘pseudo-rationalistidea’,5andRobertBishop,who says‘ourbestphysical theories areterriblyambiguous regarding the status of physical determinism’.6 But note that I am not taking the logicalpositivisthardlinethattheideaofdeterminismiscognitively meaningless – for it is an idea that we quite easily form and under- stand – but rather that we arrive at it by a process of abstraction or idealisation from the empirical realities that we actually deal with.7 It can never be directly applicable to them, though it can serve as an ideal to be approached but never actually reached. As we have seen, the definition of determinism requires the conception of a totalstate-descriptionoftheuniverseatanyonetime.Thatcontains twoidealizations–totheidealofdescribingallthestates,andofde- scribingeachparticularstateexactlyasitis.Andthereisathirdideal- ization, to the idea of acomplete set of laws of nature. Let me first address the ideal of exact description. This surely implies measurement, for although there are plenty of everyday de- scriptions which do not involve numbers (e.g. ‘purple’, ‘noisy’, ‘fragrant, ‘annoying’, ‘celebrity’, ‘sexy’), most serious science in- volves assigning numerical values to empirical quantities, using instruments of various degrees of sophistication, from rulers and thermometers up to the likes of electron microscopes and Geiger counters. But how precise can measurement be? Technology is con- stantly improving, we are constantly told, but even the most skilled operatorof the most up-to-date piece of kit hasto admit, if pressed, that her observations are accurate only within a certain margin of error. The realist metaphysician maysay in his lofty way that this is only a matter of gross human senses and gadgets, and that there remains a distinction between physical reality and our approximate measurements of it. His claim would presumably be that there is in principleanabsolutelypreciseanswerforeveryquestionofmeasure- ment, and he will have to allow that the numerical values will typi- cally go into decimal points. But how far into that infinite range? There is no theoretical limit, so the conceivable answers stretch into the rational numbers, and perhapsthe reals. Realist-minded philosophersmaystillwanttosaythattheseprac- tical limits on our knowledge of the present and predictions of the 5 Nancy Cartwright, The Dappled World (Cambridge: Cambridge UniversityPress,1999),6. 6 Robert Bishop, Chapter 4 of The Oxford Handbookof Freewill, 2nd edition,ed.RobertKane(Oxford:OxfordUniversityPress,2011),94. 7 SeetheindexreferencestoabstractionandidealizationinCartwright, HowtheLawsofPhysicsLie(Oxford:OxfordUniversityPress,1983). 435 Leslie Stevenson futuredonotaffecttheunderlyingfactsabouthowrealityis‘initself’. Somemaysaythatforallweknow,theworldmaybecompletelyde- terminate in all respects; others maystoutly maintain that it must be so.Ontheotherhand,MichaelDummett(whodevelopedthenotion of‘anti-realism’)hasdescribedtheassumptionthateverymeasurable quantitymusthaveaprecisevaluegivenbyarealnumberas‘arealist fantasywhich,thoughdeeplyembeddedinourthinking,mustbere- jected’.8Ifso,itisaniceironythatrealism,whichissupposedtobein the business of acknowledging realityas it is, may become fantastic, i.e.outoftouchwithreality.9Butthereareatleasttwokindsofdis- sociation between thought and reality: we may underestimate what thereis,orwemayoverestimateit.(Thethesisthatacertain‘transcen- dental’kindofrealisminvolvesdeepphilosophicalerroriscentralto thethoughtofKant,butwehaveyettoseeifthathasanyrelevanceto ourtopic.)Dummettisboldenoughtosuggestthatrealityitselfmay beincertainrespectsindeterminate–andhewasnotthinkingofcau- sally undetermined events, but of intelligible questions to which there is no true or false answer. Idonotknowanywayofresolvingthisstandoffbetweenrealistand anti-realist over exact measurement. The realist claim can hardly be classedasmeaningless,foritseemsintelligible(andphilosophers’at- tempts to draw sharp limits around the meaningful do not have a promising track-record). The anti-realist will point out that the rea- list’s claim can never be confirmed or disconfirmed by experience, but the realist will not be fazed by that, for it was part of his view fromthestartthatthetruthonsomemattersmayforeveroutrunem- piricaltest.Perhapsthebesttheanti-realistcandoistoshowthatthe idea of absolutely precise measurement plays no essential role in our actual dealing with theworld, not even in the most theoretical parts of science. To be sure, science expresses laws in the form of math- ematical formulas, and computations can be performed in idealized cases (in textbook examples and school homework) by feeding numbersintotheequations.Butwhenitcomestotestingtheempiri- calvalidityofthoselawsorusingthemtopredictanything,wehaveto useactuallymeasuredvaluesofgrossphysicalstuff,andthesecanonly 8 MichaelDummett,ThoughtandReality(Oxford:OxfordUniversity Press,2006),87.(Whatacapacioustitleforaslimvolume!) 9 IamremindedoftheNorthernIrishstoryaboutauniversitystudent ofengineering who got talking to themen digging up theroad outside his department; when he remarked that in his work he had to be accurate to withinthethousandth partofaninch,thefellowatthebottomofthehole replied:‘Youseislucky!Inourworkwe’vegottabedeadon!’ 436 Who’s Afraid of Determinism? be accurate only within a margin of error, and should not be strictly identified with numbers as abstractly conceived of. Itistempting tosuggestthattheidea ofexactmeasurementfunc- tions as a Kantian ideal, to be approximated to but never actually reached. But even that is open to question, for although it sounds like good advice to say that we should make our measurements as accurateaspossible, ourstandards ofprecision willquite reasonably vary depending on what we are measuring and for what purpose: there will be no point in trying to measure the width of a road or the height of a growing child to hundredths of a centimetre. And even when it is important to micro-measure with the best available kit, in cosmology or atomic theory for example, new technology may increase our accuracy but we never get any nearer to coming up with an infinite row of decimals, for the distinguishing feature of an infinite set is that however many members of it you go through, there always remain infinitely many more. Thusthe math- ematical ideal of complete precision is not asymptotically ap- proached, but constantly recedes over the horizon. Letmenowcomebacktotheideaofatotalstate-descriptionofthe worldatatime.Theclaimwouldbethattherealwaysisamonstrously large (yet presumably still finite) proposition, consisting of a con- junction of all the true propositions about the world at a time. Such propositions must outrun the conceptual resources of any human language. There were electrons and stars in the universe, androcksanddinosaursontheearth,longbeforehumansdeveloped concepts of them. And we have to allow that the sciences will prob- ably develop new concepts in future, to identify aspects of reality that presently lie beyond our ken but are all around us now. Conceptual innovation is not confined to the sciences, either: con- sider the concepts of bassoon, A minor scale, symphony, cobalt blue, golden section, pointillism, cubism, tragedy, sonnet, novel, general election, prime minister, fascism, insurance contract, sub- primemortgage,paedophilia,andsoapopera.Eachoftheseconcepts hasdevelopedatsomestageofhumanhistory,andifourhistorycon- tinues there will no doubt be new concepts, of which of course I cannotyetgiveexamples.Isubmitthatthenotionofastupendously large proposition conjoining all the truths about everything, invol- ving all the concepts that are not just actual but possible, is a very great idealization indeed. Itmaybesuggestedthatwecancutdowntheimaginedsupersetof all facts to a more manageable size by saying that the state-descrip- tions in any realistic thesis of determinism will have to prescind from any such riot of aesthetic, political and sociological concepts, 437 Leslie Stevenson and should be expressed austerely in terms of basic physical terms that apply universally to the matter and energy of which everything is composed. This raises a cluster of profound issues centring roundreductionismandemergence,aboutwhichcloudsoftechnical philosophycontinuetobegenerated.HereIcanonlygesturetowhat seemtobethemainissues.Thereisfirstlyaquestionwhetherwecan ever be sure that we have identified the most basic level of physical reality, for the history of science show a series of steps down the levels, and though the much-hunted Higgs boson now seems to be making its presence felt in the large hadron collider, there can be no guarantee that our present Standard Model of sub-atomic physics isthe end of the story. Then there are deep and difficult questions about how the pre- sumedbasiclevelrelatestotheotherlevelsofreality,fromthechemi- cal and the biological up to the psychological, social, historical, political, aesthetic – and whatever else goes into the untidy mix. If weaccepttheweakestpossibleformofmaterialismandsaythatevery- thing is composed of the entities recognized by the basic level of physics, that excludes Platonic or Cartesian dualism of mind and matter, but leaves almost everything else open. Most of us find very plausible the weakest form of supervenience – namely that if there is any sort of difference between two things or events, there must be some difference between them at the basic material level, orconversely that if theyare exactlysimilarat the bottom level they must be similar at all other levels of description. But this amounts to very little: all it implies, for example, is that if orchestra A give an exciting performance of Beethoven’s 5th Symphony whereas or- chestraB’saccountisunderwhelming,theremustbesomedifference attheacousticlevelbetweenthosetwosound-events–whichishardly news.Ifweimaginetwopossiblestatesofthewholeuniverseidentical in every physical respect, then if we believe in supervenience we would have to say that there could not be any difference between them in any other respect. Yet it would not follow that their non- physical properties can be deduced from a complete description at the physical level, any more than the properties of a computer – such as storing philosophical insights, subversive politics or child pornography – could be deduced from acomplete knowledge of the electronics of its innards. When physicists and cosmologists talk with their sublime arro- gance of ‘a Theory of Everything’, I make bold to suggest that they do not literally mean what theysay. It is not part of the ambition of physics to explain why Mozart’s early Quintet for Piano and Wind is such a great work, why therewere economic recessions after 1929 438 Who’s Afraid of Determinism? and 2007, or why Edward VIII decided to abdicate the British throne. Physical theories are not about such humanly interesting stuff, but about boring measurable quantities of mass, length, time, charge, and radiation. And even in the realm of such physical facts, there are still deep problems in the notion of a Theory of Everything. A scientific theory, as Stephen Hawking himself admits,10 is a humanly-constructed model which exists only in our minds, but tries to economically explain a large class of past obser- vations interms ofa small numberof assumptions and toaccurately predict future observation. Up till now, all physical theories have been partial, they have only tried to explain a large but limited class of physical phenomena. Moreover, the computing of the observa- tional implications of a physical theory involves approximations and simplifying assumptions, as doesthe setting up of experimental apparatus, as Hawking concedes11 and Cartwright documents in detail.12 Adjudicating the fit or lack of fit between a theory and reality is a messy business, both conceptually and technologically. So there seems to be no real prospect of a theory that is complete rather than partial, and fits observations exactly rather than approximately. ThisisconnectedwiththethirdidealizationIidentified,totheset ofallthelawsofnature.Firstofall,someepistemologicalmodestyis again appropriate. Can we derive all the higher-level laws, for example that all men are mortal, that it hardly ever rains in the deserts of Peru, or that sugar dissolves in water, from a certain set of fundamental, basic-level laws – which these days would be at the sub-atomic quantum level? If ‘derive’ means ‘mathematically deduce’, that is an enormous task that so far as I know is in most cases nowhere near completed. Indeed it is often difficult to know where to start, because contingent empirical assumptions have to be brought in, for example about the ocean currents in the Pacific Ocean, and which such assumptions are we to make in each case? Moreover,canweeverbesurethatevenourbest-confirmedscientific theory has identified all the fundamental laws of nature? Nancy Cartwright has vigorously argued that what we like to think of as thefundamentalexceptionlesslawsofnatureformulatedbytheoreti- cal physics are not even literally true of the physical world, but are 10 StephenHawking,ABriefHistoryofTime(London:BantamPress, 1998),11. 11 Hawking,op.cit.note11,187,204. 12 Cartwright,HowtheLawsofPhysicsLie(Oxford:OxfordUniversity Press,1983),Chapters1and6. 439