Kim J. 1989 the Myth of Nonreductive Materialism

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The Myth of Nonreductive MaterialismAuthor(s): Jaegwon KimSource: Proceedings and Addresses of the American Philosophical Association, Vol. 63, No. 3(Nov., 1989), pp. 31-47Published by: American Philosophical AssociationStable URL: http://www.jstor.org/stable/3130081.

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THE MYTH OFNONREDUCTIVE MATERIALISM

JaegwonKimBrownUniversity

Presidential ddressdelivered efore heEighty-seventhnnualCentralDivisionMeeting f theAmericanPhilosophical ssociationn Chicago, llinois,April28, 1989.I

Reductionismof all sorts has been out of favor for many years. Few among us wouldnow seriouslyentertainthe possibility hat ethical expressionsare definable,or reduciblein some broadersense, in termsof descriptive r naturalistic xpressions. I am notsure how many of us can remember, n vivid enough detail, the question that was oncevigorouslydebated as to whether so-called physical-objecttatements are translatableinto statements about the phenomenalaspectsof perceptual xperience,whetherthese areconceived as sensedata or as some mannerof beingappeared o . You may recall theidea that concepts of scientifictheories must be reduced,via operationaldefinitions , ointersubjectivelyperformable procedures whose results can be ascertained throughobservation. This soundedgood-properly ough-mindedandhard-nosed-but t didn't takelong for philosophersand scientists to realize that a restrictiveconstraintof this sort wasneither enforceablenor necessary-notnecessaryto safeguard cience from the threat ofmetaphysicsand pseudo-science. These reductionismsare now nothing but museumpieces.In philosophyof mind, too, we have gone through manyreductionisms;ome of these,such as logical behaviorism,have been defunct for manyyears;others, most notably thepsychoneural dentity theory, have been repeatedlydeclareddead;and still others, suchas versionsof functionalism,are still hangingon, thoughwith varyingdegreesof difficulty.Perhapsas a result of the singularlack of success with which our earlier reductionisteffortshave been rewarded, negative imageseems to have emergedforreductionismsngeneral. Many of us have the feeling that there is something rigidand narrow-mindedabout reductioniststrategies. Reductionisms,we tend to feel, attempt to imposeon usa monolithic, strait-jacketedview of the subject matter, the kind of cleansed and tidypicture that appeals to those obsessed with orderliness and discipline. Perhaps this

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APA PROCEEDINGS,VOL. 63, NO. 3impressionhas somethingto do with the reductionists' itual incantations of slogans likeparsimony , simplicity , economy ,and unity , all of them virtues of a ratherpuritanical ort. Perhaps, oo, reductionisms reout of step with the intellectualstyle ofour times: we strive for patterns of life and thought that are rich in diversity andcomplexityand tolerant of disagreementand multiplicity. We are apt to think that thereal world is a messyplace and resistsany simplisticdrive,especiallyone carriedon fromthe armchair,towardsimplificationand unification. In fact, the word reductionismseems by now to have acquired a negative, faintly disreputable flavor-at least inphilosophyof mind. Beinga reductionist s a bit like beinga logical positivistor memberof the Old Left-an aura of doctrinairenaivete hangs over such a person.At any rate, reductionism n the mind-bodyproblemhas been out of fashion for twodecades; it has been about that long since the unexpectedly early demise of thepsychoneural dentitytheory,a doctrine advertisedby its proponentsas the one that wasin tune with a world view adequately informed by the best contemporaryscience.Surprisingly,he abandonmentof psychoneuralreductionismhas not led to a resurgenceof dualism. What is curious,at least in termsof the expectationsset by the earliermind-body debates, is the fact that those who renounced reductionismhave stayed withphysicalism.The distinctive feature of the mind-body heories that have sprungup in thewake of the identity theoryis the belief,or hope, that one can be an honest-to-goodnessphysicalistwithout at the same time beinga reductionist. In fact, a correctand realisticview of science as it is practicedwill show us, the new physicalistsassureus, that as anaccount of the cross-level elationbetweentheories,classical reductionism s untenableeverywhere,not just about the psychophysical elation. The leading idea in all this hasbeen the thought that we can assuageour physicalistqualms by embracing ontologicalphysicalism ,lhe claim that all that exists in spacetime s physical,but, at the same time,accept property ualism ,a dualismaboutpsychologicalandphysicalattributes, nsistingthat psychologicalconcepts or properties orm an irreducible,autonomous domain. Theissue I want to explore here is whether or not a robustphysicalistcan, consistentlyandplausibly, wearoff reductionism-thats, whetheror not a substantialform of physicalismcan be combined with the rejectionof psychophysical eduction.To lay my cards on the table, I will arguethat a middle-of-theroadpositionof the sortjust described s not available. Morespecifically,I will claim that a physicalisthas onlytwo genuine options,eliminativismand reductionism. That is, if you have alreadymadeyour commitment to a version of physicalismworthyof the name, you must accept thereducibilityof the psychologicalto the physical,or, failing that, you must consider thepsychologicalas fallingoutsideyourphysicalisticallyespectableontology. Of course,youmight decide to reconsideryourcommitment to physicalism; ut I will not here considerwhat dualist alternativesthere might be which are still live options for us. So if I amright, the choices we face concerningthe mind-bodyproblemare rather stark:there arethree-dualism,reductionism,and eliminativism.

1. ThroughoutI will be using physicalism nd materialism and their cog-nates) interchangeably;imilarly, mental nd psychological .

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PRESIDENTIALADDRESSESII

Pressures rom two sources have been largelyresponsible, believe, for the decline ofreductionism n philosophyof mind, a decline that began in the late 1960's. One wasDonald Davidson's anomalismof the mental ,the doctrinethat there are no preciseorstrict laws about mental events.2 Accordingto Davidson, the mental is anomalousnotonly in that there are no laws relatingmental events to other mental events but nonerelatingthem to physicalevents either. This meant that no nomological inkagesbetweenthe mental and the physicalwere available to enable the reductionof the former to thelatter. The second antireductionistpressurecame from a line of argumentbased on thephenomenonof multiplerealizability f mental states which HilaryPutnam forcefullybrought to philosophical attention, claiming that it directly refuted the reductivematerialismof Smart and Feigl.3 JerryFodor and others have developed this idea as ageneralantireductionistargument,advancingthe claim that the specialsciences ,suchas psychology, ociology,andeconomics,are in generalirreducible o physicaltheory,andthat reductivematerialism,or typeidentity theory , s generallyfalse as a theory aboutscience.4 Earlierphysicalistswould have regarded he irreducibility s evidence showingthe mental to be beyond the pale of a scientificallyrespectableontology; that is, theywould have inferredeliminativismfrom the irreducibility. This in fact was Quine'sresponse to the problemof intentionality.5 But not for the latter-dayphysicalists: orthem, the irreducibilityonly meant that psychology,and other special sciences, areautonomous , nd that a physicalist an, in consistencyandgood conscience, accept theexistence of these isolated autonomousdomains within science.Let us beginwith Davidson. As noted, the anomalismof the mental can be thoughtof as the conjunctionof two claims:first,the claim that thereareno purelypsychologicallaws, that is, laws connecting psychologicalevents with other psychologicalevents, andsecond, the claim that there are no laws connecting psychologicalevents; with physicalevents. The second claim, which we might call psychophysical nomalism , s what

2. See Davidson, MentalEvents n Essayson Actionsand Events(Oxford:Oxford UniversityPress, 1980). This paperwas first published n 1970.3. See Putnam, TheNature of Mental States in Mind,Language, nd Reality:Philosophicalapers,vol. II (Cambridge:CambridgeUniversityPress, 1975). Thisarticle was firstpublished n 1967.4. JerryFodor, SpecialSciences, or the Disunityof Science as a WorkingHypothesis ,Synthese28 (1974): 97-115. See also RichardBoyd, Materialismwithout

Reductionism:What PhysicalismDoes Not Entail ,Readingsn Philosophy f Psychology,ed. Ned Block (Cambridge:HarvardUniversityPress, 1980).5. As it is the responseof some recent eliminativists; ee, e.g., Paul Churchland,EliminativeMaterialismand the PropositionalAttitudes ,Journalof Philosophy 8(1981): 67-90.

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APA PROCEEDINGS,VOL. 63, NO. 3underliesDavidson'sargumentagainstreductionism. The argument s simpleand direct:the demise of analytical behaviorism scotched the idea that the mental could bedefinitionallyreduced to the physical. Further,psychophysical nomalismshows that anomologicalreduction of the mental isn't in the offingeither. The implicit assumptionabout reduction n this argument s one that is widelyshared:reduction of one theorytoanother requiresthe derivationof the laws of the reduced theory from those of thereducer, and for this to be possible, terms of the first theory must be appropriatelyconnected via bridgeprinciples ,with those of the second. And the bridge principlesmust be either conceptuallyunderwrittenas definitions,or else express empirical awlikecorrelations( bridgeaws or theoretical dentities ).6This is all pretty straightforward.What was strikingwas the further philosophicalconclusions Davidson inferred rom these considerations. Far fromderivingsome sort ofdualism,he used them to arguefor a materialistmonism. His argumentis well known,but it bearsrepeating. Mentalevents, Davidsonobserved,enter into causalrelationswithphysicalevents.7 But causal relations must be backed by laws; that is, causal relationsbetween individualevents must instantiate lawful regularities. Since there are no lawsabout the mental, either psychophysicalor purely psychological,any causal relationinvolvinga mental event must instantiatea physicallaw, from which it follows that themental event has a physical description,or falls undera physicalevent kind. From thisit furtherfollowsthat the event is a physicalevent. Foran event is physical(or mental)if it falls under a physicalevent kind (or a mental event kind).It follows then that all events are physicalevents-on the assumptionthat every evententers into at least one causal relation. This assumptionseems entirely unproblematic,for it only leaves out events that are both causelessand effectless. If there are any suchevents, it is difficult to see how their existence can be known to us; I believe we couldsafely ignore them. So imagine a Davidsonianuniverse of events: all these events arephysical events, and some of them are also mental. That is to say, all events havephysical properties, and some have mental propertiesas well. Such is Davidson'scelebrated anomalousmonism .

Davidson'sontologyrecognizes ndividual vents as spatiotemporal articulars.And theprincipalstructureover these events is causal structure;the networkof causal relationsthat interconnect events is what gives intelligiblestructure to this universe of events.What role does mentality play, on Davidson's anomalous monism, in shaping thisstructure? The answer:None whatever.For anomalousmonism entails this: the very same networkof causal relationswouldobtain in Davidson'sworld if you were to redistributemental propertiesover its eventsany way you like; you would not disturb a single causal relation if you randomlyand

6. The classic source on reduction is ErnestNagel, The Structure f Science(NewYork:Harcourt,Brace & World, 1961), ch. 11.7. Actually the argumentcan proceedwith a weakerpremiseto the effect thatmental events enter into causal relations,either with physicalevents or with othermental events.

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PRESIDENTIALADDRESSESarbitrarilyeassignedmentalpropertieso events,or even removedmentality entirelyfromthe world. The fact is that under Davidson'sanomalous monism, mentality does nocausal work. Remember: n anomalousmonism,events arecauses or effectsonly as theyinstantiatephysical aws,and this means that an event'smentalpropertiesmakeno causaldifference. And to supposethat alteringan event's mental propertieswould also alter itsphysicalproperties nd therebyaffect its causal relations s to supposethat psychophysicalanomalism,a cardinaltenet of anomalousmonism,is false.8Anomalous monism, therefore,permitsmental propertiesno causal role, not even inrelation to other mental properties.What does no causalwork does no explanatoryworkeither;it may as well not be there-it'sdifficult to see how we could miss it if it weren'tthere at all. That thereare in this worldjust these mental events with just these mentalcharacteristics s somethingthat makes no causal differenceto anything. On anomalousmonism,that an event falls under a given mental kind is a causally irrelevantfact; it isalso somethingthat is entirely inexplicable n causal terms. Given all this, it's difficultto see what point there is in recognizingmentalityas a feature of the world. I believethat if we push anomalousmonism this way, we will find that it is a doctrinevirtuallyindistinguishableromoutrighteliminativism.Thus, what we see is this: anomalous monism, rather than giving us a form ofnonreductivephysicalism, s essentiallya formof eliminativism. Unlike eliminativism, tallowsmentalityto exist; but mentalityis given no usefulwork and its occurrenceis leftwhollymysteriousandcausallyinexplicable. This doesn'tstrikeme as a formof existenceworthhaving. In this respect,anomalousmonism does ratherpoorlyeven in comparisonwith epiphenomenalismas a realism about the mental. Epiphenomenalism ives themental a place in the causal network of events; the mind is given a well-definedplace,if not an active role, in the causal structure of the world.These observationshighlightthe importanceof properties;orit is in terms of propertiesand their interrelations hat we make sense of certain concepts that are crucial in thiscontext, such as law, causality, explanation,and dependence. Thus, the anomalousnessof mental propertieshas far-reaching onsequenceswithin Davidson'sframework:withinit, anomalouspropertiesare causallyand explanatorily mpotent,and it is doubtful thatthey can have any useful role at all. The upshot is that we don't get in Davidson's

8. Davidsonsays in MentalEvents hat he believes in the supervenience fthe mental on the physical,and this does introducea constraint on the distributionofphysicalpropertieswhen the distributionof mental properties s altered. This,however,does not detract substantivelyfrom the point being made here. For one, itremainstrue, on the notion of supervenienceDavidsonfavors (which corresponds oweaksupervenience ;ee his Reply o EssaysX-XII n Essayson Davidson:Actionsand Events,ed. Bruce Vermazenand MerrillB. Hintikka (Oxford:Oxford UniversityPress, 1985)), that the removalof all mental properties romevents of this worldwould have no consequencewhateveron how physicalpropertiesare distributedoverthem. For another, the supervenienceof the mental is best regardedas an indepen-dent thesis, and my presentremarksonly concern the implicationsof anomalousmonism. I considerthe supervenienceview below in IV.

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APA PROCEEDINGS,VOL. 63, NO. 3anomalous monism a plausibleform of nonreductivephysicalism;his anomalousmonismcomes perilouslyclose to eliminativism.9

IIILet us now turn to the multiple realizability (or compositionalplasticity ) ofpsychologicalevents and its implications or psychophysical eduction. In a passagethatturned out to have a profound impact on the discussionsof the mind-bodyproblem,Putnam wrote:10Considerwhat the brain-statetheoristhas to do to make good his claims. He has tospecifya physical-chemicaltate such that anyorganism not just a mammal)is in painif and only if (a) it possessesa brainof a suitablephysical-chemical tructure;and (b)its brain s in that physical-chemicaltate. This means that the physical-chemical tatein questionmust be a possiblestate of a mammalianbrain,a reptilianbrain,a mollusc'sbrain (octopusesare mollusca,andcertainlyfeel pain), etc. At the same time, it mustnot be a possible (physically possible) state of the brain of any physically possiblecreature that cannot feel pain. Even if such a state can be found, it must benomologicallycertainthat it will also be a state of the brainof any extraterrestrialifethat may be found that will be capableof feeling pain beforewe can even entertainthe suppositionthat it may be pain.

This paragraph elped bringon an unexpectedlyearlydemise of the psychoneuraldentitytheoryof Smart and Feigland inspireda new theoryof the mental, functionalism,whichin spite of its assorteddifficulties s still the most influentialpositionon the nature of themental.11 Putnam'sbasic point is that any psychologicalevent-type can be physicallyrealized or instantiated r implemented n endlesslydiverseways, dependingon thephysical-biologicalnature of the organismor system involved, and that this makes it

9. Davidson'soverall views of the mental are richer and more complex than thepresentdiscussionmight seem to indicate. I believe that they contain some distinctlydualisticelements; for a discussionof this aspect of Davidson,see my PsychophysicalLaws n ErnestLePore and BrianMcLaughlin,eds., Actionsand Events:PerspectivesnthePhilosophyf DonaldDavidson(Oxford:Blackwell, 1984). There have been someinterestingrecent attempts,which I cannot discusshere, to reconcile anomalousmonism with the possibilityof mental causation;see, e.g., ErnestLePoreand BarryLoewer, MindMatters , ournalof Philosophy4 (1987): 630-642; BrianMcLaughlin,TypeEpiphenomenalism,Type Dualism, and the Causal Priorityof the Physical ,

forthcoming;Terence Horgan, MentalQuasation , orthcoming.10. Pumam, TheNature of Mental States .11. Putnam himself has abandoned unctionalism; ee his Representationnd

Reality(Cambridge:MIT Press, 1988), chs. 5 and 6.

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PRESIDENTIALADDRESSEShighlyimplausible o expect the event to correlateuniformlywith, and thus be identifiablewith, some single ype of neural or physicalstate. This idea has been used by Fodorto formulatea generalantireductionistargument,whose gist can be quicklysummarized.

As we have seen, reduction of one theory to another is thought to require thederivation of the laws of the reducedtheory from the laws of the reducervia bridgelaws . If a predicate of the theory being reduced has a nomologically coextensivepredicate n the reducingtheory, the universallyquantifiedbiconditionalconnecting thetwo predicateswill be available for use as a bridge aw.12Let us say that the vocabularyof the reducedtheoryis strongly onnected with that of the reducingtheory if such abiconditionalbridge aw correlateseach predicateof the formerwith a predicateof thelatter. It is clear that the condition of strongconnectibilityguaranteesreduction(on theassumptionthat the theory being reduced is a true theory). For it would enable us torewrite basic laws of the target theory in the vocabularyof the reducer, using thesebiconditional aws in effect as definitions. Either these rewrites are derivablefrom thelaws of the reducing theory,or else they can be addedas additional basic laws. In thelatter case, the reducer theory has been expanded; but that does not diminish theontological and conceptual importof the reductiveprocedure.But what multiple realizationputs in doubt, according to the antireductionist,isprecisely he strongconnectibilityof mentalpredicatesvis-a-visphysical-neural redicates.For any psychologicalproperty, here is in principlean endlesssequenceof nomologicallypossiblephysicalstates such that, thougheach of them realizes r implements t, noneof them will by itself be coextensive with it. Why can't we take the disjunctionf thesephysicalstates as the physicalcoextension of the mental property? Putnam somewhatdisdainfullydismisses this move, saying only that this does not have to be takenseriously .13 think there are some complex issues here about disjunctivepredicatesvs.disjunctiveproperties,complexityof predicatesvs. that of properties,etc.; but these arelikely to be contentious issues that can only distract us at present.14So let us go alongwith Putnam here and disregardthe disjunctivesolution to the multiple realizationproblem.

12. There are some complex logical and ontologicaldetails we are leaving outhere. See, for details, Robert L. Causey, Unityof Science(Dordrecht:Reidel, 1977).13. TheNature of Mental States ,p. 437.14. Note also that derivationalreductiondoes not require trongconnectibility;any set of bridge aws, of whateverform and strength,will do as long as it enables the

requiredderivation. But this obviously dependson the strengthof the two theoriesinvolved, and there seems to be little of interest that is sufficientlygeneral to sayabout this. There are also philosophicalconsiderations or thinkingthat biconditionalsand attributeidentitiesare important n reduction. Cf. LawrenceSklar, TypesofInter-TheoreticReduction ,British ournalor thePhilosophy f Science18 (1967): 109-124.

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APA PROCEEDINGS,VOL. 63, NO. 3In rejecting the disjunctionmove, however, Putnam appearsto be assumingthis: aphysical tate thatrealizesa mentalevent is at leastnomologicallyufficient or it. For if this

assumptionwererejected,the disjunctionmove couldn'teven get started. This generateslaws of the form Pi - M , where M is a mental state and Pi is a physicalstate thatrealizes t. Thus, where there is multiplerealization, here must be psychophysicalaws,each specifyinga physicalstate as nomologicallysufficient for the given mental state.Moreover,Putnam'schoice of examples n the quotationabove,which are eitherbiologicalspecies or determinatetypes of physicalstructures ( extraterrestrials ),nd his talk ofspecies-specificity nd species-independence 15uggestthat he is thinkingof laws of asomewhatstronger orm, Si-, (M -. Pi) ,which,relative ospeciesor structure i, specifiesa physicalstate, Pi, as bothnecessary nd sufficientor the occurrence of mental state M.A law of this form states that any organismor system, belongingto a certain species, issuch that it has the given mental propertyat a time if and only if it is in a certainspecified physicalstate at that time. We may call laws of this form species-specificbiconditional aws. .In order to generatelaws of this kind, biologicalspeciesmay turn out to be too wide;individualdifferences n the localizationof psychological unctions in the brain are wellknown. Moreover,given the phenomenaof learningandmaturation, njuries o the brain,and the like, the neural structurethat subservesa psychologicalstate or function maychange for an individualover its lifetime. What is importantthen is that these laws arerelative to physical-biologicaltructure-types, lthoughforsimplicityI will continue to putthe matter in terms of species. The substantivetheoreticalassumptionhere is the beliefthat for each psychological tate there are physical-biologicaltructuretypes,at a certainlevel of description or specification, that generate laws of this form. I think anassumptionof this kind is made by most philosopherswho speak of multiple realizationsof psychological tates, and it is in fact a plausibleassumption or a physicalist o make.16Moreover,such an assumption eems essential to the very idea of a physicalrealization;what else could physicalrealization mean?So what I am sayingis this: the multiplerealizationargumentperhapsshows that thestrong connectibilityof mental propertiesvis-a-vis physicalpropertiesdoes not obtain:however,it presupposeshat species-specifictrong onnectibilityoes hold. Merelyto defeatthe antireductionist rgument,I need not make thissecondclaim;all I need is the weakerclaim that the phenomenonof multiple realization s consistentwith the species-specificstrongconnectibility,and it seems to me that that is plainly true.The point of all this is that the availability f species-specificbiconditional aws linkingthe mental with the physicalbreathesnew life into psychophysical eductionism. Unlike

15. TheNature of Mental States ,p. 437.16. Ned Block says, Most functionalistsare willing to allow . . . that for eachtype of pain-feelingorganism,there is (perhaps)a single type of physicalstate thatrealizespain in that type of organism ,n his Introduction:What is Functionalism? nBlock, ed., Readingsn Philosophyf Psychology,ol. 1 (Cambridge:HarvardUniversityPress, 1980), p. 172. Such a law would have exactly the form underdiscussion.

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PRESIDENTIALADDRESSESspecies-independent aws, these laws cannot buy us a uniformor global reduction ofpsychology,a reductionof every psychological tate to a uniformphysical-biological aseacross all actual and possibleorganisms; owever,these laws will buyus a seriesof species-specificor local reductions. If we had a law of this form for each psychologicalstate-type forhumans,we would have a physicalreductionof humanpsychology; his reductionwould tell us how human psychology is physically implemented, how the causalconnections between our psychological events and processes work at the physical-biological evel, what biological ubsystems ubserveourcognitivecapacitiesandfunctions,and so forth. This is reduction in a full-blown sense, except that it is limited toindividuals haringa certainphysical-biologicaltructure. I believe local reductions ofthis sort are the rule ratherthan the exception in all of science, not just in psychology.17In any case, this is a plausible picture of what in fact goes on in neurobiology,physiologicalpsychologyand cognitiveneuroscience. And it seems to me that any robustphysicalistmust expect, and demand,the possibilityof local reductionsof psychology ustin this sense.l8

Thus, the conclusion we must drawis that the multiplerealizability f the mental hasno antireductionistmplicationsof greatsignificance; n the contrary, t entails,or at leastis consistentwith, the local reducibility f psychology, ocal relative to speciesor physicalstructure-types.Ifpsychological tatesaremultiplyrealized, hat only means that we shallhave multiple local reductionsof psychology. The multiple realizationargument, if itworks, shows that a global reductionis not in the offing;however, local reductionsarereduction enough, by any reasonable scientific standards and in their philosophicalimplications.IV

Some have looked to the idea of supervenience or a formulationof physicalism hatis free of reductionistcommitments. The promiseof supervenience n this area appearsto have been based,at least in part,on the historicalcircumstance hat some prominentethical theorists,such as G.E. Moore and R.M. Hare,who constructedclassic argumentsagainst naturalisticreductionism n ethics, at the same time held the view that moralproperties re supervenient pondescriptiveor naturalisticproperties.So whynot thinkof the relationbetweenpsychologicalandphysicalpropertiesn analogywith the relation,as conceivedby these ethical theorists,betweenmoral anddescriptiveproperties?In eachinstance, the supervenientpropertiesare in some substantive sense dependent on, ordeterminedby, theirsubvenient,base propertiesand yet, it is hoped, irreducible o them.

17. See on this point Berent Enc, InDefense of the IdentityTheory ,JournalofPhilosophy 0 (1983): 279-98.18. This point, and some relatedpoints, are elaborated n my DisunityofPsychologyas a WorkingHypothesis? ,orthcoming.

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APA PROCEEDINGS,VOL. 63, NO. 3This was preciselythe line of thinkingthat appears o have promptedDavidson to injectsupervenience nto the discussionof the mind-bodyproblem. He wrote:19

Although the positionI describedenies there are psychophysicalaws, it is consistentwith the view that mentalcharacteristics re in some sensedependent,or supervenient,on physical characteristics. Such superveniencemight be taken to mean that therecannot be two events alike in all physical respects but differing in some mentalrespects,or that an objectcannot alter in some mentalrespectwithout altering n somephysicalrespect. Dependenceor supervenienceof this kinddoes not entail reducibilitythrough aw or definition: f it did,we could reducemoralproperties o descriptive,andthis there is good reason to believecannot be done . . .

Although Davidsonhimselfdid not pursuethis ideafurther,manyother philosophershavetried to work this suggestiveidea into a viable formof nonreductivematerialism.The central problem n implementingDavidson'ssuggestionhas been that of defininga superveniencerelation that will fill the twinrequirements e set forth:first,the relationmust be nonreductive;hat is, a given domain can be supervenienton another withoutbeing reducible to it. Second, the relation must be one of dependence:f a domainsuperveneson another, there must be a sturdysense in which the first is dependentonthe second, or the second determinesthe first. But it has not been easy to find such arelation. The main difficulty has been this: if a relation is weak enough to benonreductive, t tends to be too weak to serveas a dependencerelation;conversely,whena relation is strong enoughto give us dependence, t tends to be too strong-strongenoughto imply reducibility.I will not rehearsehere the well known argumentspro and con concerningvarioussuperveniencerelations that have been proposed. I will instead focus on one superve-nience relation that has seemed to several philosophers20ly to hold the most promiseas a nonreductivedependencyrelation, viz., globalsuperve-nience . The genericidea of supervenience s that thingsthat are indiscerniblen respectof the base (or subvenient )propertiescannot differ in respect of the supervenient

19. MentalEvents , n Davidson,Essayson Actionsand Events,p. 214.

20. IncludingTerence Horganin his Supervenience nd Microphysics , acificPhilosophical uarterly 3 (1982): 29-43; John Haugeland n WeakSupervenience ,AmericanPhilosophical uarterly19 (1982): 93-103; John Post in The Facesof Existence(Ithaca:Corell UniversityPress, 1987); and BradfordPetrie, GlobalSupervenienceand Reduction ,Philosophynd Phenomenologicalesearch 8 (1987): 119-130. Themodel-theoreticnotion of determinationworkedout by GeoffreyHellman and FrankThompson, in Physicalism:Ontology, Determination,and Reduction , ournalofPhilosophy 2 (1975): 551-564, is closely related to global supervenience.

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PRESIDENTIALADDRESSESproperties. Global supervenienceapplies this considerationto worlds ,giving us thefollowingformulationof psychophysical upervenience:

Worlds that are indiscerniblein all physical respects are indiscerniblein mentalrespects; n fact, physically ndiscernibleworldsare one and the same world.Thus, any world that is just like this world in all physicaldetails must be just like it inall psychologicalrespectsas well. This relation of supervenience s appropriately alledglobal n that worlds rather than individualswithin worlds are comparedfor discern-ibilityor indiscemibility n regardto sets of properties. What is it for two worlds to bephysically, or mentally, indiscernible? For simplicity let us assume that the sameindividualsexist in all the worlds:21We may then say that two worlds are indisceriblewith respect to a set of propertiesjust in case these propertiesare distributedoverindividuals n the same way in the two worlds.It can be shownthat, as hoped,the globalsupervenienceof the mental on the physicaldoes not entail the existence of psychophysical aws;22 hus, global supervenience isconsistent with the nomologicalirreducibility f the mental to the physical. The onlyquestion then is whether it yields an appropriate elation of dependencybetween themental and the physical,one that is strong enough to qualifyit as a physicalism. Theanswer,I will argue, is in the negative.We may begin by observingthat the global supervenienceof the mental permitsthefollowing: Imaginea world that differsfrom the actual world in some minute physicaldetail. We may supposethat in that world one lone hydrogenatom somewhere n deepspace is slightly displacedrelative to its position in this world. This world with onewaywardhydrogenatom could, consistentlywith the global supervenienceof the mental,be as different as you please from the actual worldin any mental respect (thus, in thatworldnothing manifestsmentality,or mentalityis radicallyredistributed n other ways).The existence of such a worldand other similarlyaberrantworlds does not violate theconstraintsof global supervenience; ince they are not physically ndiscernible rom theactual world, they could, underglobal supervenience,differradicallyfrom this world inpsychologicalcharacteristics.23

21. Even with this simplifyingassumptioncertain complicationsarise;however,we may disregard hem for the presentpurposes. For furtherdetails see my Superve-nience for MultipleDomains ,Philosophicalopics16 (1988): 129-150.22. At least not in a straightforward ay. See my 'Strong' nd 'Global'

SupervenienceRevisited ,Philosophynd Phenomenologicalesearch 8 (1987): 315-326.23. This particulardifficultycan be largelymet by formulatingglobal superve-nience in terms of similarity etween worldsratherthan indiscemibility. See my'Strong'and 'Global'SupervenienceRevisited .

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APA PROCEEDINGS,VOL. 63, NO. 3If that doesn't convinceyou of the weaknessof global supervenienceas a determinationor dependencyrelation,consider this: it is consistent with globalsupervenience or thereto be two organismsn our actual worldwhich, thoughwhollyindiscerniblephysically,are

radicallydifferent n mental respects(say, yourmolecule-for-moleculeduplicateis totallylacking in mentality). This is consistentwith global superveniencebecause there mightbe no other possibleworld that is just like this one physicallyand yet differing n somemental respect.24It seems to me that indisceribility considerationsat the global level, involvingwholeworlds,are just too coarse to give us the kind of dependencyrelation we shoulddemandif the mental is truly dependenton the physical. Like it or not, we treat individuals,andperhapsalso aggregates f individuals mallerthan total worlds,as psychologicalunits, andit seems to me that if psychophysicaldeterminationor dependence means anything, itought to mean that the psychologicalnatureof each such unit is wholly determinedbyits physicalnature. That is, dependencyor determinationmust hold at the local as wellas the global level.Moreover, alk of whole worlds n this connection, unless it is anchored n determina-tive relationsobtainingat the local level, has little verifiablecontent; it is difficultto seehow there can be empiricalevidence for the globalsupervenience hesis that is not basedin evidence about specific psychophysicaldependencies-dependencies nd correlationsbetween specific psychologicaland physical properties. In fact, it seems to me that wemust look to local dependencies or an explanation f globalsupervenienceas well as itsevidence. Why is it the case that no two worldscan exist that are indiscerniblephysicallyandyet discerniblepsychologically?Or why is it the case that physical ruthsdetermineall the truths, 25s some preferto put it? I think this is a legitimatequestion to raise,and as far as I can see the only answer,other than the response that it is a brute,unexplainable metaphysical fact, is in terms of local correlations and dependenciesbetweenspecificmental andphysicalproperties.If the global supervenienceof the mentalon the physicalwere to be proposedas an unexplainable act that we must accept onfaith, I doubt that we need to take the proposalseriously. Specific psychophysicaldependencies holding for individuals,and other properparts of the world, are bothevidence for, and an explanatorygroundof, global supervenience.The trouble s that once we begintalkingaboutcorrelationsand dependenciesbetweenspecific psychological ndphysicalproperties,we are in effect talkingaboutpsychophysicallaws, and these laws raise the specterof unwantedphysicalreductionism. Where thereare psychophysicallaws, there is always the threat, or promise, of psychophysicalreduction. We must conclude that supervenience s not going to deliver to us a viableform of nonreductivematerialism.

24. This shows that global supervenience s consistentwith the failure of weaksupervenience .See my 'Strong' nd 'Global'SupervenienceRevisited .

25. See Hellman and Thompson, Physicalism:Ontology, Determination,andReduction ;Post, The Facesof Existence.

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PRESIDENTIALADDRESSESV

So far I have reviewed three influential formulationsof nonreductive materialism-Davidson'sanomalousmonism, he Putnam-Fodor octrineof psychological utonomy,andsupervenientphysicalism-and ound each of them wantingeither as a materialismor asa antireductionism. In this final section, I want to advance a direct argumentto showwhy the prospectsfor a nonreductivephysicalismare dim.Let us first of all note that nonreductivephysicalisms not to be a formof eliminativ-ism;that is, it acknowledges he mental as a legitimatedomainof entities. What sort ofentities? Here let us, forconvenience,make use of the Davidsonianscheme of individualevents, thinkingof mentality to be exhibited as propertiesof these events. Thus, as anoneliminativist, the nonreductive physicalist believes that there are events in herontology that have mental properties e.g., beinga pain, beinga belief that snow is cold,etc.). I argued earlier, in discussing Davidson's anomalous monism, that if yournoneliminativism s to be morethan a tokengesture,you had betterfind some realcausalwork for your mental properties. The fact that a given event is a mental event of acertainkindmust playsome causal-explanatoryole in what other events occur and whatproperties hey have. Thus, I am supposingthat a nonreductivephysicalist s a mentalrealist,and that to be a mental realist,your mental propertiesmust be causalproperties-properties n virtue of which an event enters into causal relations t would otherwisenothave entered into.Let me now make another assumption:psychophysical ausation takes place-that is,some mental events cause physicalevents. Forexample,a suddensharp pain felt in myhand causes a jerkywithdrawalof the hand. It is true that in a Davidsoniandomain,all events are physical; hat is, every event has some physical property. But when I saythat mental events cause physicalevents, somethingstronger s intended,namely that anevent, in virtueof its mentalproperty, auses another event to have a certain physicalproperty. I believe that this assumptionwill be grantedby most of us-it will be grantedby anyonewho believes that at least sometimesour limbs move because we have certaindesires and beliefs.26When I walk to the water fountain for a drink of water, my legsmove in the way they do in partbecause of my desirefor water and my belief that thereis water to be had at the water fountain.There is a furtherassumptionthat I believe any physicalistwould grant. I call thisthe causal closure of the physicaldomain ;roughly,it says this:any physical ventthathas a causeat timet has a physical auseat t. This is the assumptionthat if we trace thecausal ancestryof a physicalevent, we need never go outside the physicaldomain. Todeny this assumption s to accept the Cartesian dea that some physicalevents have onlynonphysicalcauses, and if this is true there can in principlebe no complete and self-sufficientphysicaltheoryof the physicaldomain. If the causal closurefailed,our physicswould need to refer in an essentialway to nonphysicalcausal agents, perhapsCartesian

26. For a forcefulstatement of this point see FredDretske, ExplainingBehavior:Reasons n a Worldof Causes (Cambridge:MIT Press, 1988).

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APA PROCEEDINGS,VOL. 63, NO. 3souls and theirpsychicproperties,f it is to give a completeaccount of the physicalworld.I think most physicalistswould find that pictureunacceptable.Now we are readyto derivesome consequencesfromthese assumptions. Supposethata certain event, in virtue of its mental property,causes a physicalevent. The causalclosure of the physicaldomain says that this physicalevent must also have a physicalcause. We may assume that this physicalcause, in virtue of its physicalproperty,causesthe physicalevent. The following question arises:What is the relationshipetweenthesetwocauses,one mentaland the otherphysical?Each is claimed to be a cause of the physicaleffect. There are two initial possibilities hat we can consider.First, when we are faced with two purportedcauses of a single event, we couldentertain the possibility hat each is only a partial ause, the two together making up afull or sufficientcause, as when a car crash is said to be caused by the driver'scarelessbrakingand the icy condition of the road. Applied to our case, it says that the mentalcause and the physicalcause are each only a partialcause, and that they togethermakeup one sufficient cause. This seems like an absurdthing to say, and in any case itviolates the causal closure principle n that it regards he mental event as a necessaryconstituent of a full cause of a physicalevent; thus, on this view, a full causal story ofhow this physicalevent occurs must, at least partially,go outside the physicaldomain.Could it be that the mental cause and the physicalcause are each an independentsufficient ause of the physicaleffect? The suggestionthen is that the physicaleffect isoverdetermined. o if the physicalcause hadn'toccurred, he mental cause by itself wouldhave caused the effect. This picture is again absurd:from what we know about thephysiologyof limb movement,we must believe that if the painsensation causes my handto withdraw, he causalchain from the pain to the limb motion must somehow make useof the causal chain from an appropriate entral neural event to the muscle contraction;it makes no sense to think that there was an independent,perhapstelekinetic, causalpath from the pain to the limb movement. Moreover, he overdeterminationdea seemsto violate the causal closureprincipleas well: in the counterfactual ituationin which thephysicalcause does not occur, the closure principle s violated. For the idea that themental and the physical cause are each an independentsufficient cause involves theacceptanceof the counterfactualthat if the physicalcause had not occurred,the mentalcause would have occurred and caused the physicaleffect. This is in violation of thecausal closure principle.These two ways of lookingat the situationare obvious nonstarters. We need a moreplausibleanswer to the question,how are the mental cause and the physicalcause of thesinglephysicaleffect related to each other? Given that any physicalevent has a physicalcause, how is a mental cause also possible? This I call the problem of causal-explanatoryexclusion , for the problemseems to arise from the fact that a cause, orcausal explanation, of an event, when it is regardedas a full, sufficient cause orexplanation,appears o excludeother independenturported auses or causalexplanationsof it.27

27. This idea is developedin greaterdetail in my Mechanism,Purpose,andExplanatoryExclusion ,Philosophicalerspectives (1989), forthcoming.

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PRESIDENTIALADDRESSESAt this point, you mightwant to protest:why all this beatingaroundthe bush? Whynot just say the mental cause and the physicalcause are one and the same? Identifica-tion simplifiesontology and gets ridof unwantedpuzzles. Considersayingthat there are

in this glass two distinct substances,HO2and water;that is, considersaying that waterand H20 co-occur everywhereas a matter of law but that they are distinct substancesnonetheless. This would invite a host of unwanted and unnecessarypuzzles:given thatwhat is in the glass weighs a total of ten ounces, how much of the weight is to beattributedto the waterand how much to the H20? By droppinga lightedmatch in theglass, I extinguishit. What caused it? Was it the water or the H2O? Were they eachonly a partial cause, or was the extinguishingof the match overdetermined? Theidentificationof the water with the H20 puts all these questionsto rest in a single stroke:there is here one thing, not two. The identitysolution can work similarmagic in ourpresent case: the pain is a neural state-here there is one cause, not two. The limbmotion was causedby the pain, that is to say, by a neural state. The unwantedpuzzlesvanish.All this is correct. But what does the identitysolution involve? Remember hat whatis for us at issue is the causalefficacyof mentalpropertiesf events vis-ai-vis heirphysicalproperties. Thus, the items that need to be identified are properties-that s, we wouldneed to identifymental propertieswith physical properties. If this could be done, thatwould be an excellent way of vindicatingthe causal powersof mentality.But this is precisely the route that is barred to our nonreductivist friends. Theidentification of mental propertieswith physicalproperties s the heart of reductionisttype physicalism .These property dentities would serve as bridge aws par excellence,enablinga derivationalreductionof psychology o physical theory. The identitiesentailpsychophysical orrelationsof biconditional orm,stable over possible,or nomologicallypossible,worlds,and this,we have been told, is excludedby Davidson'smental anomalismand Putnam's multiple realizationargument. So the identity solution is out of thequestionfor the nonreductivematerialist. Is thereanyotherway to respond o the causalexclusion problem,a way that falls short of identifyingmental with physicalattributes?There is one, but it isn't somethingthat would be palatableto the nonreductivist. Ibelieve that the only way other than the identitysolution is to give a generalaccount ofcausalrelations nvolvingmacro-eventsas supervenient ausalrelations , ausalrelationsthat are supervenienton micro-causalprocesses. You put a kettle of water on the stoveand turn on the burner;and soon the water starts to boil. Heating the water caused itto boil. That is a causal relation at the macro-level. It is natural to think of this causalrelation as supervenienton certain underlying ausal processesat the micro-level. Theheatingof watersuperveneson the increasingkineticenergyof watermolecules,andwhentheir mean kinetic energy reaches a certain level, water molecules begin to move inturbulence, some of them being ejected into the air. Boiling is a macro-state thatsuperveneson just these micro-processes. A sharp pain causes an anxiety attack fiveseconds later. What's going on? Again, it is tempting,and natural, to think thus: thepain is supervenienton a certain underlyingneuralactivity,and this neural event causesanother neural event to occur. The anxietyattack occurs because it is supervenientonthis second neural event.The generalmodel of supervenientcausationappliedto macro-causalrelationsis this:macro-eventm is a cause or effect of event E in virtueof the fact that m is supervenient

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APA PROCEEDINGS,VOL. 63, NO. 3on some micro-event,n, which is a cause or effect of event E.28 The suggestionthen isthat we use this model to explain mental causation: a mental event is a cause, or aneffect, of another event in virtue of the fact that it is supervenienton some physicalevent standingin an appropriate ausal relation to this event. Thus, mental propertiesare seen as deriving their causal potential from the physical propertieson which theysupervene. That is the main idea.But what sort of superveniencerelationis involved in this picture? Global superve-nience we consideredabove obviouslywill not do; it does not give us a way of speakingof supervenienceof specificmental properties n specificphysicalproperties, ince it onlyrefers to indiscemibilityholdingfor worlds. Supervenientcausationin my sense requirestalk of specificmental properties uperveningon specificphysicalbaseproperties,and thisis possibleonly if there are laws correlatingpsychologicalwith physical properties. Thisis what I have called elsewhere strongsupervenience ,and it can be argued plausiblythat supervenienceof this strengthentails the possibilityof reducingthe supervenienttothe subvenient.29 will spareyou the detailshere, but the fact that this form of superve-nience directly nvolvespsychophysicalaws wouldbe enough to give pause to anywould-be nonreductivephysicalist. I am not entirelycertainthat this supervenience olutionwillsuffice; that is, I am not certain that anythingshort of the identity solution will resolvethe exclusionproblem. However,I believe that it is the only alternativeto exploreif, forwhateverreason,you are unwillingor unable to go forpsychophysical ttribute identities.But I doubt that this solution will be found acceptable by the nonreductivistany morethan the identity solution.

28. For critical discussionsof this model, see BrianMcLaughlin, EventSuperve-nience and SupervenientCausation ,Southern ournalof Philosophy 2, The SpindelConferenceSupplementn Supervenience1984): 71-91; Peter Menzies, AgainstCausalReductionism ,Mind 97 (1988): 560-574.29. I am putting the point somewhat tentativelyhere because it involves severalcurrentlycontentious issues. For a general argumentfor this point, see my Conceptsof Supervenience ,Philosophynd Phenomenotogicalesearch 5 (1984): 153-176;

especially,section III;and Supervenience s a PhilosophicalConcept ,forthcoming nMetaphilosophy.However, this argumentmakes use of infinite disjunctionsandconjunctions (actually,infinite disjunctionsare all one needs;see Supervenience s aPhilosophicalConcept ). If the argument s found objectionablebecause of thisfeature, it could be supplementedwith an argumentmodeledon my argumentinsection III above against the Putnam-Fodorantireductionist hesis. This means thatthe superveniencerelationneeded for the model of supervenientcausationsketchedhere must requirethat each supervenientpropertyhave a nomologicallyoextensive aseproperty elative o thegivenphysical tructure. There are, I believe, plausibleconsider-ations in favorof this strongersuperveniencerelationas a basis for the concept ofsupervenientcausation(orthe reductionof causal relations);however, I cannot go intothe details here.

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PRESIDENTIALADDRESSESIf nonreductivephysicalistsaccept the causalclosureof the physicaldomain, therefore,

they have no visible way of accounting for the possibilityof psychophysicalcausation.This means that they must either give up their antireductionismor else reject thepossibilityof psychophysical ausal relations. The denial of psychophysical ausationcancome about in two ways:first,you make such a denial becauseyou don't believe thereare mental events; or second, you keep faith with mental events even though youacknowledge that they never enter into causal transactions with physical processes,constituting their own autonomous causal world. So either you have espousedeliminativism,or else you are movingfurther n the direction of dualism,a dualismthatposits a realm of the mental in total causal isolation from the physical realm. Thisdoesn't look to me much like materialism.Is the abandonmentof the causal closure of the physicaldomain an option for thematerialist? I think not: to reject the closure principle is to embrace irreduciblenonphysicalcauses of physical phenomena. It would be a retrogression o Cartesianinteractionistdualism,somethingthat is definitive of the denialof materialism.Our conclusion, therefore,has to be this: nonreductivematerialism s not a stableposition. There are pressuresof various sorts that push it either in the direction ofoutrighteliminativismor in the direction of an explicit form of dualism.30

30. My thanks to RichardBrandt,SydneyShoemaker,and ErnestSosa forhelpful comments on earlierversions,and to David Benfield,BarryLoewer,and BrianMcLaughlin or discussingwith me some of the topics of this paper.

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Documents

Kim J. 1989 the Myth of Nonreductive Materialism