T. Place

Australasian Journal of Philosaphl Vol. 66, No. 2: June 1988

THIRTY YEARS ON -

IS CONSCIOUSNESSSTILL A BRAIN PROCESS? U . T . Pl a c e

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was publishedin the Brifish Journol of Psychologyfor February 1956r.This papertogetherwith HerbertFeigl'spaper"The'Mental'and the'Physical'" which appearedin Volume II of the Minnesota Studiesin the Philosophy of Science2 and Jack Smart'spaper 'sensationsand Brain Processes'which appearedin PhilosophicalReviewin 19593are generallyheld to be the three primary sourcesin recentphilosophicalliteraturefor the materialistor identity view of the mind-brainrelationship,There is thereforesomejusticein the claim that thesethreeand my own, ás the first to be publishedin particular, may be regardedas ancestralto the materialism that has becomea widely acceptedestablishmentview in contemporaryphilosophy, particularly in the United States.Thesedays wheneverthe broadcastingmedia in the United Kingdom do a featureon the mind-body problem it is a virtual certaintythat it will be a philosopher,suchas Dan Dennettor John Searle,who presents the materialistposition. The only thorough going dualist they seemto be ableto find is the brain physiologistSir John Eccles,with the psychologist, if thereis one, sittingasusualon the fence.Truly a remarkabletransformation from the situation that existedthirty yearsago, when everyphilosopheryou met was quite convincedthat whateveranswerto the mind-body problem, if there is one, is true, materialismmust be false. Contemporaryphilosophicalmaterialism,however,is a horse of a very different colour from the thesisI was arguing for in my 1956paper. Two striking differencesstand out. In the first place, the thesisI was arguing for was restrictedin its applicationto mental events,to sensations,mentalimages and thoughtoccurrences and the associated activitiesof thinking, imagining and paying attention in as far as they are covert or hidden from the view or hearingof another person. Mental states,I assumedfollowing Ryleo,are dispositions,eithercapacities analogousto a car'shorsepoweror tendencies like the car'stendencyto understeerwhich are causallydependenton features I U. T. P l a c e , ' I sc o n s c i o u sn e ss ' it¡ shJo u r n a lof P sychotogyX LV II, 1956, a b r a in p r o ce ss?Br pp. 44-50 2 H. F e i g l ," T h e ' m e n t a l ' a n d th e ' p h ysica l' ."In H. F e ig l, M . Scri venand C . Maxw el l (eds.), MinnesotaStudiesin the Philosophyof ScienceYol.II, Minneapolis,Universityof Minnesota Press, 1958, pp- 37O-497. I J. J. C. Smart,'sensations and brain processes.'PhilosophicatReview LXylll, 1959,pp. l4t - l 5 6 . a G. Ryle, The Concept of Mind, London, Hutchinson, 1949.

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f the car's internal structure, but which are not the same thing as those pipe is internal featuresin the way that the explosion in the car's exhaust Contemporary backfires. when it which we hear the same event as that materialistsby contrast have followed David Armstrong in his 1968book general A Materialist Theory of the Miné in holding that mental states in unknown with the particular identical are in propositional attitudes and featuresof the brain microstructureon which, on my view, they are causally dependent.The only exceptionhere is John Searle,who both in his 1983 claimsto hold both of these,in my book6and in his 1985Reith LecturesT Accordingto Searie,mentaistai€s theoriessimuitaneousiy. vlsw,incompatibie States u irponthe corresponding Cependent ith r-¡rtrsáll)' anri iCentic:rl b,oih are of the brain. I say you can't haveyour cakeand eat it. Either mentalstates areidenticalwith brain statesor one is causallydependenton the other. They can't be both. of extendingthe identity theory from its original One of the consequences events so as to cover mental states,is that whereasit mental to restriction is not too difficult to suggestwhat sort of a brain event something like a sensationor a mental image might be supposedto consist in, if you try to imagine what sort of a brain state some thing like my belief that it's going to rain tomorrow might be supposedto consistin, the mind quickly begins to boggle. We are confronted with the apparently insoluble philosophical problem of how the intentionality which is a prominent feature of mental statescan possibly be construedas a property of the brain microstructure' on the view that I hold by As I seeit, this problem is neatly side-stepped showing (l) that that there are a number of mental event verbs, like 'paying attentionto', 'watching','looking at', 'listeningto', 'savouring',etc. which do not display this feature, and (2) that wheneverthe grammatical object of a mental event verb ¡s intentional, it turns out that the intentionality is invariably attributable to a mental stateor dispositionwhich is involved in the mental event rather than to the mental event as such. Thus wherevera mental event characterisedby reference to an intentional object, the intentionalobject turns out to be either (a) a simile used to indicate the way the individual is inclined to characterisean experience,as in the casewherea pain is characterised by referenceto the part of the body from which it appearsto emanate, (b) the objective of a disposition with which a mental activity is performed,as in the caseof 'looking for something', the belief, intentionor other (c) an embeddedsentence which characterises disposition which is brought into being by a mental event, as when D. M. Armstrong, A Materialist Theory of the Mlnd, London, Routledgeand Kegan Paul,

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J. R. Searle,Intentionality: An Essoyin the Phitosophy of Mind, cambridge, cambridge U ni versi tyP ress,1983,pp. 264-2 7l . J. R. Seaile.Minds, Brainsand kience: the 1984ReithLectures,LondoÍt, B.B.C. Publications, 1984, pp.20-23.

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Thirty YearsOn - Is Consciousness Still a Brain Process? a decisionis characterised by referenceto the intentionto do something in which it results.

If to this is added the demonstrationby John Burnheimsand more recentlyby C. B. Martin and K. Pfeiferethat physicaldispositionsand their descriptionsbear all the marks of intentionality mentioned by such philosophersas ElizabethAnscomber0,Roderick Chisolmrrand Bill Lycanrz, and we reachthe conclusionthat intentionalityis the mark, not, as Brentano thought, of the mental,but of the dispositional13. Combinethis with Ryle's th e si st hat dis pos it io n aslta te me n ts a re c o n c e a l e h d y pothet;calrvhi s chI sri i i thinf., i¡¡i¡¡¡\r

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i n h i s 1968book , is a trn a b l eri e r..' a n dri re-,e .' .,:d p ro ' C i ern ci ' i ni enti onal r,, becomesa problem about the role of dispositionalstatementsin causal judgments,not in any way specificto the mind-body problem. I do not expectthis way of side-stepping the problemof intentionalityto recommenditself to philosophersany more than my contentionthat the thesis that consciousness is a brain processis an empirical scientifichypothesis recommendeditself to philosophersin the nineteenfifties and sixties,even those like Smart who were in generqlwell disposedtowardsthe materialist position. The reasonfor this is that my objectivesin putting forward the thesisin the first placewas and is diametricállyopposedto the interestsof 8 ln an unpublishedpaper entitled'lntentionality and Materialism'presented to the Department , of Ph i l o s o p h ya t t h e U n ive r sityo f Syd n e yc. 1 9 6 9 . v In their paper'lntentionality and the non-psychological', Philosophy and Phenomenological . ^ Res e a r c hX L V I , 1 9 8 ó ,p p . 5 3 1 - 5 5 4 . 'u C. E . M . A n s c o m b e ,' Th e in te n tio n a lityo f se n sa tio n s.'In R . J. B utl er (ed.'¡A natyti col . . P hilo s o p h y ,S e c o n dS e rie s,Oxfo r d , Bla ckwe ll, 1 9 6 5 ,p p . 1 5 8-180(usedby B urnhei m). " R. Chisholm, Perceiving:a PhilosophicalStudy.lthaca, Cornell UniversiryPress,1957(used by Martin and Pfeifer). r2 W. G, Lycan, "On'intentionality'and the psycholcgical."American Philosophicalquarterty . _ 6, 19 6 9 ,p p . 3 0 5 - 3 1I ( u se db y M a r tin a n d Pfe ife r ) . '' I n ¡h e l i g h t o f a n a r g u me n td e ve lo p e db y Rich a r d Ga r r e tt in hi s paper 'E l bow room i n a functional analysis:freedom and dignity regained'(Behaviorism 13, 1985,pp. 2l-36) which in turn derievesfrom an argument developedby Donald Davidson in his'Rational animals) (Diateclica36, 1982,pp. 317-327\,1 am now inclinedto think rhat ir is only what Searle(Mind LX X X V l l l , 1 9 7 9 ,p p . 7 4- 9 2 ) ca lls' in te n tio n a lir y- wir h - a {wh ' ic h i s i nvari abl yrhe mark of the dispositional. I would, however, want to argue that any open ended predicateswhich (Searle),referentiallyopaque(Quine)or non-Shakespearean are intensional-with-an-s (Ceach) by the criterion of failure of substitutabilitysalva veritate are being used non-referentially as a linguistic devicefor characterisingthe scopeof a disposition. But, in the caseof proper names and definite descriptionsused to characterisea particular individual towards whom or which behaviour is directed, it appears,in the Iight of the Davidson-Garrettargument, that a different explanation of the failure of substitutabilitysalva veritate is required. The suggestionis that in thesecasesfailureof substitutabilityis evidencethat the nameor description in question is being used as an indirect quotation of the name or descriptionby whrch the individual is known to the agentwhosebehaviouraldispositionsare being described.On rhis ac c ou n tt h e " t r a n s p a r e ncy"o f th e n a m e sa n d d e fin ited e scr ip tionsusedi n characteri sati ons of t he b e h a v i o u r a d l i s p ositio n so f a n im a ls,to wh ich Da vid so nand Garett draw attenti on, is explainedby the fact that where, as in the caseof animals, there is no name or descriprion by which a particular individual is known to the agent, there is no reason for singling out any one name or description as the "correct" way to characterisethe agent'sbehavioural orientation towards that individual. 14P. T. Ceach, Mental ,4cls, London, Routledge and Kegan paul, 1957.

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philosophersin this matter. For what I was trying to do was to clearaway the tangle of philosophicalobjectionswhich, as I saw it, were impeding empirical researchin neurophysiologyand physiologicalpsychologyaimed at discoveringthe physicalnature of consciousness and its location within the brain. This objectiverequiresthe effectiveliquidationof the mind,/body problemas a philosophicalissueso that it can be handedoverasan empirical issucto be resolvedby the neuro-scientist. Needlessto say, philosophershave a vestedinterestin preciselythe oppositeobjectiveof keepingthe mind-body ¡r" ot1ernas r l i r e phi l osop hical issue . It i s thi s needto retai nthe mindzbodt 'pr oblem asa ! ii'elhiloso! ¡ hical i, s, sue ancito presei vethe statusof t he philosopheras t he r elevantexper tin such matters which, in my view, explains the remarkable turn around in philosophicalattitudesto materialismwhich can be dated rather precisely to the publicationof Armstrong'sbook in 1968.Before 196g,virtually all the philosophicalliteratureon the identity theory washostile;after l96g more and more philosophers beganto climb on to the materialistbandwagon.For once the identity thesisis extendedfrom the identity of mentaleventswith brain eventsto the identity of mental stateswith brain states.the insoluble philosophicalproblem of explaininghow a propositionalattitude could possiblybe construedas a stateof the brain allowsthe philosopherto adopt the materialistposition without losing his statusas the relevantexpert in mattersof intentionalityand its representation in the brain. It is in this light that I read such bizarre theories as Davidson'sAnomalous MonismtJ. Dennett'saccountof brain functioningin terms of the combinedeffectsof the decisionsof a committeeof homunculir. and Fodor's innately preprogrammedlanguageof thought.r? But the aspectof this revolutionin philosophicalattitudeswhich I want to focus upon relatesto the other major respectin which contemporary phiiosophicalmaterialismdiffers from the materialismI was advocatingin 1956.As I have alreadymentioned,in the 1956paper and my 1960reply to Jack Smart'spapermy contentionwasthat materialismasappliedto mental eventsis a reasonablescientifichypothesiswhich cannot be ruled out ofcourt by a priori philosophicalargument. Not only was that the only part of the thesisof my 1956paperwhich Smart criticisedin his 1959paper, it is also one of the featuresof the original thesiswhich is conspicuouslymissingfrom contemporary philosophical versions of materialism. contemporary philosophical materialists are inclined to treat the empirical evidenceof mental/cerebral correlation as irrelevant to the issueswith which they are concernedand seekto demonstratethe truth of materialismby meansof a purely a priori argument of which Davidson'sargument for this principle ¡5 D. Davidson, 'Mental events.'In L. Fosterand J. w. Swanson(eds.)Experienceand rheory, London, Duckworth, 1970.Reprintedin D. Davidson, Essayson Acrions and Evenrs,oxford, ._ O.U .P ., 1980,pp.207-227. 'o D. c. Dennett, Bra¡nsrorms:Phitosophicot Essayson Mind and psychotogy. Montgomery, ._ V ermont, B radford B ooks, 1978. " J. A . Fodor, The LanguageofTh ought. N ew y ork , C row el l . 1975.

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Thirty |'ears On - Is Consciousness Still u Bruin Process?

of anomalous monism is a prime example. Although its a priori character and the effect of its conclusion, the conclusion that there are no psycho-physicalbridge laws, in nullifying any empirical evidence of psycho-physicalcorrelation is clear enough, the argument itself is notoriously difficult to state. As I read it, it divides into two parts of which only the secondis at all explicitly stated.Part l, goes roughly as follows: l. E v er y hum a n a c ti o nh a so n e o r mo re p roposi ti onalatti tudesas its immediatecause. 2. F i, er yhum a n a c i i o t h a s a b ra i rl s l a i e a s i ts r¡n¡neci i are aaus:. 3. Eventscannot have more than one immediatecause. ERGO 4. The setof propositionalattitudeswhich constitutethe immediate causeof a particularhuman action are identicalwith the brain state which constitutesthe immediate causeof that action. Part 2 then proceedsas follows: 5. All causationpresupposesa universallyquantified causal law relating eventsor statesof the causetype to statesor eventsof the effect type. 6, No such universallyquantified causallaw can be stated relating propositional attitudes to the action types they cause. 7. Universallyquantifiedcausallawscan, however,be statedrelating brain statesand eventsto the action types they cause. ERGO 8. No universallyquantified law statementcan be true which relates particular brain stateswith which they are (by 4 above)identical. In other words there are no psycho-physicalbridge laws. I acceptthat both theseargumentsare valid. I am also myself committed, as I shallexplainlater, to a versionof the argumentin Part l, though with mental eventsrather than propositional attitudes or mental statesas its subject matter. However I reject both conclusions,in eachcasebecauseI reject one of the premisesfrom which is it deduced. In the case of Part I I reject conclusion 4 becauseI reject premise3; and I reject premise 3 because,on my view, the brain state which causesan action is an indirect rather than an immediate causeof the action it leads to. The immediate cause is the propositional attitude or mental state and that state is causally dependent on, not identical with the state of the brain the microstructure. In the caseofPart 2, I rejectthe conclusion8. partly becauseI rejectthe prior conclusion4 which assertsthe identity of the propositionalattitude and the brain state on which, in my view, it depends,but partly also becauseI reject proposition 6. The reasonfor this is that I hold that a propositional attitude statementor indeedany dispositionalstatementis itself a universally quantified causallaw in the sensethat is requiredfor the truth of proposition 5. All that a causaljudgment requires,in my view, is a statementwhich is universallyquantified over eventsor statesof the types to which the causal

LI. T. Place

213

judgment relates.It mattersnot if the eventsin questionare restrictedto the behaviourof a particularindividual or to the limited window of time constitutedby the duration of the particulardispositionin question. ln other words dispositionalstatementsof which propositionalattitude statementsare a sub-varietyarestatementsof the form: 'If at any time between t, and tn causalconditionc, combineswith causalconditionsc, . . cn, an eventof the e type will occur.'A statementof this form is all that is required to deducethe counterfactual:'If at any time betweentr and tn the causal condi ti onsci cnhad beenf ulf iiled.an evenrof t he e t - vpewould have occur¡ed'whicii ioiiowilg jt-rirrrivíackie", i iake ro be whar is meanr by .

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of the e type. I want to emphasisethis analysisof causaljudgmentsnot only because of its relevancefor my rejection of Davidson'sa priori argument for anomalousmonism, but also because,as we shallsee,it playsa crucialrole in the argumentto which I proposeto devotethe remainderof this paper. This argument is in effect my third and I hope finally successfulattempt to rebut the objectionthat Jack Smart raisedin his 1959paperto my contention that materialismis an empiricalscientifichypothesiswhosetruth or falsity will ultimatelybe demonstratedone way or the other by the empiricalevidence of neurologicaland psycho-physiological research. As those who have read Smart'spaper will rememberre, the argument runs roughly as follows. Smart beginsby concedingthat the issueas to whetherconsciousness is to be locatedin the heart, the liver, the brain or in some other organ of the body is an empiricalissue.That issuehe takes to have alreadyhavebeenconclusivelydecidedin favour of the brain. But the real issueis not the issuebetweenthe liver thesis,the heart thesisand the brain thesislit is the issuebetweenthe view that mentaleventsare identical with some,as yet unsp€cifiedphysicaleventswhetherin the brain, heart, liver or elsewhereand the view that they are mereepiphenomenaor causally ineffectiveby-productsof the physicaleventswith which they are correlated. With respectto thal issue,he maintains,any evidencewhich is consistent with the identity thesiswill also be consistentwith epiphenomenalism. No crucialexperimentis conceivablewhich would enableus to decidethe issue betweenthe two theories.The situation is comparedwith the issuebetween the explanation of the fossil record in terms of the theory of evolution and the explanation of the fossil record in terms of Gosse'stheory accordingto which the fossilrecordwas laid down by the Creatorat the Creationof the Universein 4004 BC in order to test the faith of l9th century Christians. In such cases,Smart maintains, there is and can be no decisiveempirical evidenceeitherway. The only thing we can do is to appealto the principle of Ockham's razor to eliminate the more complex and ontologically less economicalhypothesisin favour of the simpler and ontologicallymore economicalone. rE J. L. Mackie, Counterfactualsand causallaws. In R. J. Butler (ed.) Anatyricot Philosophy, First Series.Oxford, Blackwell, 1962, pp. 6ó-80. re S mart, op. ci t. pp. 155-156.

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Thirty YearsOn - Is Consciousness Still a Brain Process?

When I replied to this objection in my 1960 paper "Materialism as a scientific hypothesis"2o, I concededthat the crucial issuewith respectto the truth of the mind-brain identity thesisis whether or not the thesismakessense , not whetheror not it will be supportedby the empiricalevidence.To concede this, I now think, was to concedethe substanceof Smart'sobjectionand thus allow the focus of discussionto be steeredaway from the empirical evidenceand towards the purely philosophicalissues.Over the years,as the debatehas developed,I havecome increasinglyto think that this was a false move; and it wasin this spirit that I returnedto the issuein a paperenrirled 'Twenty yc¿r¡s ü¡i - is cot¡sciousrrcss siiii a brain proccss?'whicili reaciar University College,London anci at the Urriversity'oi Clasgowdurrrrgiire course of 1976 and which was eventually published in a journal, now, I believe, defunct, called Open Mind, published by the Open Universitfr. Perhaps the best way to give you the flavour of this secondattempt to reply to Smart'sobjection is to quote the opening paragraph'sof the paper as it was publishedin 1977:Sincethe discoveryof the electroencephalogram by Hans Bergerin 1929 we now know beyondall reasonabledoubt what had long beensuspected, namely: that whenevera human being epgagesin some kind of mental activity such ¿rsperforming an arithmetical calculation in his head, or simply paying attention to sensory stimulation in one or other of the sensorymodalities,thereis a correspondingchangein the patternof neural activity in his brain. And although we are still a long way from the stage of beingable to reada man'sprivatethoughtsfrom a study of the electrical activity in his brain, the complexityand varietyof the patternsof electrical acfivity revealedby the electroencephalogram are more than sufficient to justify the belief that all the complexity and variety of the thought processes andconsciousexperiencesof an individual human being are exactly and completelyreflectedin the complexity and variety of the concurrentbrain activity. More recently,the developmentof computer technologyand the theory of artificial intelligencehas made it possibleto explain how the brain might be supposed to carry out virtually all those operations traditionally attributed to the mind. At the sametime neurologicalevidence of the way in which behaviour and intellectual performancedepend on the integrity and proper functioning of the brain as a whole and its constituentparts has shown beyond all reasonabledoubt that intellectual performanceand behaüour are generatedand controlled by the brain not merely, as Descartessupposed,at the level of tactical execution,but at the level of strategicdecision also. Facedwith evidencesuch as this, it is no longer possibleto hold with Descartesthat when a man thinks, there are two quite distinct processes 20 U. T. Place,'Materialism as a scientific hypothesis.'Philosophicat ReviewLXIX, 1960,pp. I 0t - 1 0 4 . 2r U. T. Place, 'Twenty yearson - is consciousness still a brain process?'Open Mind 6, 1917, pp. 3 - 1 0 .

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taking place,namely, a mental processwhich strictly speakinghas no extensionor positionin physicalspaceand which constitutesthe thought processas it appearsin the consciousness of the individual in question, and a concomitantphysicalprocesslocatedin his brain whosefunction with information from is merelyto providethe separatementalprocesses the senseorgansabout the currentstateof the environmentand organise the executionof the appropriatemovementsof the body whenthe mental processhas reachedthe point of decidingwhat to do. (Place1977,p' 3) (-',rrrrir-1,-'rq'f that is sr-rggesting as r,.rep!1to Sna,rt'sobjectionIhis a,rgtrment may be \\'hrlethe lssuebet\\'eenthe ldentltv theory and eDtDhenomenaltsm s,t her eis anot herissuenam eiyt he as S iniarciaim i ei npi ri i ri i ' ,i i ¡rurci i i cabi e, issuebetweenthe identitytheoryand Cartesiandualistinteractionismwhich and is in processof beingdecidedin favour of the u empiricall¡-decideable What showsis that whenevera mental process view. the evidence identity a corresponding brain processwhich hasthe samedegree there occurs occurs of complexityasthe mental processreportedby the subject,hasall the causal propertiesrequiredto generatethe behaviourwhich the mental processis condition is a causallynecessary supposedto generateand whoseoccurrence for the occurrenceof that behaviour. However, this evidencecan only be used to demonstratethe falsity of dualistinteractionism,if thereis an o priori principlewhich can be invoked in order to excludethe possibilityof two simultaneousparallel processes' one a mental process,the other a brain process,both contributingto the causationof the ultimate behaviouraloutput. Intuitively this seemsright; both and epiphenomenalism, and certainlythe adoption of psycho-parallelism of a causal protecl the existence dualism by denying which to seek of connectionbetweenmentaleventsand their apparentbehaviouraloutcome, seemsto suggestthat this intuition is widely sharedby philosopherswho have intuition, Nevertheless thoughtabout this mattersincethe daysof Descartes. howeverrvidelysharedis no substitutefor solidargument.In my 1977paper whereby I tried to deal with the problemby invoking Davidson'sprinciple22 to its causes position relative it occupies by the unique event is individuated an on the one hand and its effectson the other. As I pointed out in that paper:It follows from this principlethat you cannothavetwo eventsor processes or effects. and the sameconsequences with the sa¡necausalantecedents Now as we haveseen,the empiricalevidenceshowsthat whenevera mental processoccurstherealso occursa brain processwhich hasexactlythe same or effects as the mental causal antecedentsand the same consequences processappearsto have.But sinceby Davidson'sprincipleonly one process we can have that particular set of causalantecedentsand consequences, are compelledto concludeeither that the mental processand the brain processare one and the sameprocessor if, as most philosophershave 12 D. Davidson,'lndividuating events,'ln N. Rescher(ed.) Essalsln Honor of Carl G. Hempel, on Aclions and Evenls. Dordrecht,Reidel,1969,pp. 216-234.Reprintedin D. Davidson,Essoys Orford, O.U .P ., 1980,pp. 163-180.

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Thirty YearsOn - Is Consciousness Still u Brain Process?

held, they aretwo differentprocesses, then one of theseprocesses cannot in f,acthave the causalantecedentsand consequences that it appearsto have. (Place 1977,p. 3) Unfortunately, as my colleagueRoger White23has since convinced ¡e, this principle'sof Davidson'scannot be sustained.Roger'sobjection is essentiallyHume's point2athat the causalrelation is a relation betweentwo discreteeventsor statessuchthat whateverhappensin practiceit must always be conceivablethat the causeeventor statemight occur or be the casewithout th e ef lec t sev enror s ta teb e i n gth e c a s e It . fo l l o rv sthat e\,ents or statesw hi ch arc causaii-v rciarecimusrbe inciiviciuateci by somerhingother rhan the causal rei¡ . i i o n --^i -4 :.-_

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I'hereis, however,anotherargumentwhich can, I believe,be usedto show that the causesof an eventcannotincludemore than one event.Every event comesabout, every state of affairs is maintainedby a number of causal factors.The set of causalfactorswhich contributeto the coming about of an eventor to the maintenanceof a stateof affairs in a particularcaseare said to be sufficient for the occurrenceof that event or the maintenanceof that state of affairs. This meansthat, wheneverall the causalfactors in questionare present,an eventof the sametype will occur or a stateof affairs of the sametype will persist,whereasif any one of thosefactorsis missrng the eventwill not occur,the stateof affairs will not be maintained.In a case where the effect is a stateof affairs all the causalfactors which maintain that stateof affairs will themselves be statesof affairs. Moreover,in a case where the effect is an event, all the causal factors except one will likewise be statesof affairs which are in position,as it were, for a longeror shorter period of time prior to the coming about of the effect. There will be one and only one triggeringeventwhich completesthe setof causalfactors which are jointly sufficient for the coming about of the effect which will begin imntediately the triggering event occurs. Now if this is correct,it follows in the casewe are consideringthat when a human agent does somethingor sayssomethingas an apparentend result of a mentalprocess,if, as we havegood empiricalevidencefor thinking it is, every mental processis invariably accompaniedby a causally effective brain process,it cannot be the casethat the conclusionof both of the two distinct processes assumedto be operatinghere, acts as a triggeringevent with respectto the initiation of the agent'saction or utterance.And given the empirical evidencefor the causalefficacy of the brain processin such case,we haveto conclude,I suggest,that either the two processes are one and the same or that the mental processis causally impotent and, hence, epiphenomenalwith respectto the agent'saction or utterance. It is true that thereare two counterexampleswhich havebeensuggested to me in which two eventscan be saidto jointly trigger a singleeffect, though neither of them, it seemsto me, offer a viable way out of the dilemma I 23 P e r s o n a lc o m m u n i ca tio n . 24 Treatiseon Human Nature. Bk.l. Sec. XlV.

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havejust described.The first is the casewheretwo eventswhich act in opposite directions on the same object or substanceoccur simultaneously.For supposeyou have a balancewith the weight equally distributed example25 betweenthe two arms and two weights,which may be equal or different, fall simultaneouslyon to the two arms. The net effect will clearlybe different from what it would havebeenif only one of the two weightshad fallen on to one of the two arms. Here, it may be argued,we havean exampleof an event which is brought about by two separatetriggeringevents. N ow you mi ghtsaythat si n cet he f wo event shavet o be sim r r lfaneor t s, t his tri gg er r ng event s.but a slnglet ngger r npeventwnlch l s not real i ytw o ci i screte s ; b5 r it eLr ', '.r ."cight i s ci earl ydi fferenti ' romtl l e tr igger ingevenI sc<] r r sr it uicci But, be that as it may, this exampleis evidentlynot going falling separately. to provide a useful analogy for the caseof mental processesand brain processes, sincein the caseof the balancethe simultaneityof the falling of the two weightsis purely fortuitous; whereasit could hardly be maintained of the conclusionof the mentalprocesswith that of the that the coincidence correspondingbrain processis a matterof coincidence.A much betteranalogy by the dualistinteractionistis providedby the backup for what is envisaged computeror computerswhich are installedin spacecraftand, I believe,in some aircraft thesedays which perform the samecalculationsas the main computerand whichare usedboth as a checkon the calculationsof the main computer and as a substitutein the event of the main computerbreaking down. The casein which the ultimate output of the systemis determined on the basisof the outputsof both computersin the casewherethere are only two would then be the analogyfor the versionof dualistinteractionism in which both the mental processand the correlatedbrain processcontribute to the ultimate effect. This conceptionof the mental processas a kind of backup computer providing a checkon the calculationsmade by the main computerin the brain is not a view which is likely to satisfyeitherthe dualistor the biologist.For role the dualistit fails to givethe mentalprocessits uniqueand indispensible in the control of behaviour;for the biologistit is difficult to seewhy we should be required to postulate an extra-physicalmental processsimply to act as a backup to the brain activity,especiallywhen we know that thereis ample sparecapacityin the human brain, if such backup computationalfacilities were needed. But on this model, evenif we grant that the mental processmakesa causal from that made contributionto the final outcomewhich is distinguishable by a parallelbrain process,in the casewherethe two calculationsdisagree, the final decisionas to which of the two is to determinewhat the individual finally saysor doeshas to be made by the brain. For, as we have seen,the empirical evidencerehearsedabove shows that the brain processis both sufficient and necessaryfor the production of the verbal or behavioural output. Consequently,in a casewheretherecan be only one eventoccupying 2J I am i ndebtedto my col l eagueD r . Tony Gal ton for thi s ex ampl e.

ThirtS'YearsOtt

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a particularpositionin a causalchain, the empiricalevidencepoints fairly decisivelyto that position being occupiedby an event in the brain. But if the final decisionas to what to say or do is taken in the brain, it must be the casethat, if dualism is true, the sensewe have that our thoughtsand feelingsdetermingwhat we say and do has to be an illusion. Even if we interpret our thought processes as playing an essentialbackup role in relation to the main computerin the brain, qua mental process,the final decision on what to sayand do hasto be ephiphenomenal; and this, it may be thought, paperro the ei l eq¡ b ri n gsus r ight bac k to S m a rt' sc o n te n ti o ni n h i s 19-59 may be iruc oi rireissueberween ihar, whaLevcr inreraciionisrn aucitireicientrtl -f--_ _ _ .. l fl e ¡¡I\

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empiricallydecideable. In my 1917paperI tried to dismissboth epiphenomenalism and psychophysicalparallelismby meansof the following argument:Not only do both these theories conflict with the intuitions of in that they both deny that our thought processes commonsense, and sensationshave any effect on the way we behave;they also have the characterof thosegratuituoushd hoc assumptionscalculatedto prorect a theory from any possiblefalsification'bythe empiricalevidencewhich, as Karl Popper has repeatedlyargued, are unacceptablein a genuine scientifictheory. (Place 1977,p. 4) While I would not want to retractany part of that argumentnow, there is, so it seemsto me, anotherand more decisiveargumentagainstpsychophysicalparallelismand epiphenomenalism as tenableversionsof dualism. This is the argumentthat, if eitherof thesetheoriesweretrue, therecan be no causalconnectionbetweena mental event and the descriptionthat is purportedlygivenof that mentaleventin the subject'sintrospectivereport. But if the occurrenceof an eventis not a causalfactor in the giving of the descriptionthat purports to be given of that event,it cannot be a genuine descriptionof the eventin question.Consequentlythere is no way, consistent parallelism,wherebywe with either epiphenomenalism or psycho-physical can usethe introspectivereportsof other peopleas evidenceof the nature of their mentalprocesses in the caseof others.While thereare some,no doubt, who think that solipsismis the only consistentform of mentalism,it is hardly a strong position from which to argue for any thesiswith the object of convincinganothermind of its truth. I conclude,therefore,as I concluded i n the 1977paper:-

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to the relation betweenmental eventsand brain events.But, sincethat is preciselythe versionof the thesisto which I haveconsistently subscribedfor the past thirty two years,this is no skin off my nose.However,there is, I suspect,an alternativereplacementfor the Davidsonian principle whereby eventsare individuatedby the uniquepositionthey occupyin a causalnexus which would enablean Armstrongianto benefitfrom this line of argument. For it appearsto be a plausiblemetaphysicalprinciplethat the only properties that are predicableof eventsand statesof affairs are propertiesof a causal and temporalkind. The suggestion would be that any spatialpropertiesare -,-l:^^Ll^ lJl!Ul!dUlC

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l -..,' the erampleof t he t elephcne e,,i l l ustrated bet u, een t he LI . K. conver sat icn and A ustrai i aw hi chcannotbe plausiblylocat edin eit herplaceor anyr vher e If this is correct, we could then go on to argue that if two in between26. havethe sameonset statesor eventsinvolvethe sameindividualsubstances, and duration in time and have the samecausesand effects,sincethere are no other respects in which they can differ, they must, by Leibniz'sprinciple be one and the samestateor event as the of the identity of indiscernibles, casemay be. If I am not mistaken,what this line of argumentshowsis that the doctrine and of the impotenceof consciousness to which both epiphenomenalism parallelismare committedis not just contraryto the intuitions psycho-physical of common senseand to the requirementthat a scientifictheory be in principle susceptibleto falsification,it rendersboth theoriestotally incoherentby depriving them of any explanationof how there could be such a thing as or mental states. an individual'sself-reportof his or her own mentalprocesses are incoherentand But if psycho-physicalparallelismand epiphenomenalism if, as I am inclinedto think, the dual-aspecttheory collapsesinto the identity theory, we are left, assumingthat idealismis not a viableoption for scientific purposes,with the choice betweendualist interactionismand the identity theory; and lhat, if I am right, is an empiricalissuewhich is in processof being decidedby an increasinglyformidable body of empirical evidencein favour of the identity theory.

that the hypothesisthat mental processes are the sameprocesses as the concurrentwith them is the only hypothesiswhich is brain processes consistentwith the empiricalevidence,with our commonsense beliefthat how and what we think and feel affectswhat we say and do and with the proprietiesof scientificmethod. (Place 19'77,p. 4) It will be noted that, in so far as theseargumentsdependon ttreprinciple that there can only be one triggeringevent relativeto anothereventas effect, they only haveapplicationto a mind-brainidentity thesisthat is restricted

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26 I am indebted to my colleagueDr. Harry Lewis for this example.