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    The Southern Journal of Philosophy (2008) Vol. XLVI

    Descartes Dualism andContemporary Dualism

    Cecilia WeeNational University of Singapore

    Michael PelczarNational University of Singapore

    Abstract

    After drawing a distinction between two kinds of dualism-numericaldualism (defined in terms of identity) and modal dualism (defined inte rm s of supervenience)-we arg ue th at Descartes is a numericaldualist , but not a modal dualist . Since most contemporary dualistsadvocate modal dualism, t he relation of Descartes views to t he contem-porary philosophy of mind ar e more complex th an is commonly assumed.

    Descar tes i s r ight ly he ld to have inaugura ted the modern

    debate over the relationship between mind and body. He is alsoperceived as having been th e first, or among the first, to occupyone of th e leading positions in thi s debate: dualism. Our aim inthis essay is to show that this perception is only partly accurate.Although Descartes is certainly a dualist of some sort, he is nota dual is t as t ha t t erm is commonly understood today. Hisposition i s more complex and, in cer tain ways, more intr igu ingthan many popular expositions of his views nowadays suggest.We sh all ar gu e th a t h e would i n fact come ou t as endorsingmaterialism, as t ha t is now understood within mai nstr eamanalytic philosophy. At the same time, there is a clear sense inwhich his position is a dualist one. We conclude that theassumption that we can simply transpose Descartes philosophy

    Cec i li a Wee i s Assoc ia t e P ro fe s so r o f Ph i lo sophy a t t he Na t ion a lUniversi ty of Singapore. Sh e i s au thor o f Material Falsity and Error inDescartess Meditations (2006).

    Michael Pelczar is As sist an t Professor o f Philosoph y at the Nation alUn iversi ty of Singapore. He h as publ ished ar t icles in th e phi losophy ofm ind and the phi losophy of language.

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    of mind directly onto th e contemporary debate is faulty an d isbound to give an erroneous picture of his t rue position.

    Our paper begins by outlining two different kinds of dualism,which we will call respectively numerical and modal dualism(t he latt er being th e most representative version of dualism incontemporary debates). Correspondingly, we will different iatebetween numerical materialism and modal materialism. We willthen argu e tha t, while Descartes was a numerical dual ist , hewould also have endorsed modal materialism. We acknowledget h a t th e vas t gulf between Descartes own metaphysics a ndanything th at would acceptably pass under t h at name todaywill only allow a t best an a p p r o x i m a t e mappi ng of hi s viewsonto those preva lent in contemporary debates. We arg ue,

    nevertheless, t hat th e most approximate mapping of Descartesviews to c urr ent views would reveal t h a t his position is fa rcloser to modal materialism than to modal dualism.

    1. Varieties of Dualismand Materialism

    Broadly speaking, dual ism is the view t hat there is a n ultimatedistinction between t he mental and th e physical; materialism isth e view t h a t th ere i s no such d is t inc tion . But t h i s broad

    definition elides two these s t h at might equally well be styleddua l i s t , and two th a t can l ay equa l cl aim to the t i t l e ofmaterialism. We suggest the following definitions/distinctions:

    Numerical Dualism

    Not every mental entity (object, event, s tate, process, property,state of affairs, etc.) is one and the same as some physical entity.

    Numerical M aterialism

    Every mental entity is one and the same as some physical entity.

    Modal Duali sm

    Not every possible world that physically duplicates the actualworld contains every mental entity th at the actual world contains.

    M&l MaterialismEvery possible world that physically duplicates the actual worldcontains every mental entity tha t the actual world contains.

    The kind of possibility invoked by the last two definitions islogical possibility. To deny that something is possible in th is

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    sense is to say tha t i t is like a millions being less t han two, orazures being a shade of yellow; t o call s om eth in g logicallynecessary is to liken i t t o twos being less than a million, o r toazures being a shade of blue.

    What do we mean by physical and mental? There can beno question of definitions here; the most we can offer areinstructive tautologies. Physical st at es of affairs ar e st at es ofaffairs concerning what exists and happens, physical lyspeaking. They comprise t he facts tha t physicists would-givenenough time , bra in s, an d funding-discover. I t would be amistake t o equate physical entities with phenomena of the sortrecognized by present-day physics, since present day physics isincomplete, an d in some respects probably wrong. The physical

    domain crucially encompasses biological phenomena, such asthe structure, function, and behavior of human organisms.The te rm mental is more slippery. In one sense, a mental

    s t a t e is any s ta te whose presence explains certa in forms ofbehavior, primarily complex goal-oriented behavior. This is whatcontemporary philosophers of mind often call the psychologicalaspect of the mental. However, there is ano the r sense ofmental in which to describe something as a mental sta te is tosay tha t there is something th at it is l ike to be in th at state .This is th e phenomenal aspect of t he menta l. Hereafter, we

    use the word menta l t o cover both psychological andphenomenal aspects of the mental ; thu s, to say th at mentalphenomena a re physical is to say that every psychological andevery phenomenal state , event, property, fact, etc., is physical.2

    Modal materialism does not imply t h a t every possible worldthat physical ly duplicates the actual world duplicates itmentally. The view is compatible with the possibility of a worldphysically identical to our own th a t contains all the m en talentities t ha t our world contains plus some extra mental entities(disembodied minds, perhaps) that do not exist in our world.The modal materialist claims only that an y possible worldphysically identical to ours is a world in which t he re exist a tleast those men tal phenomena th at exist in our world. It i spossible fo r a modal materialist to make the furth er claim th atan y world physically identical t o ours is one in which th er eexist at least and at most th e mental phenomena t h a t actuallyexist, but this is not mandatory, and not a further claim t ha t allcontemporary proponents of modal materialism ar e prepared tomake.3

    How does modal m ateri alis m relat e to numerical ma teri-alism? According to numerical materialism, each mental entityis numerical ly identical to some physical ent i ty; this is astra igh tfor ward version of th e Iden ti ty Theory. Numeric almaterial ism enta i ls modal materia l ism, s ince if a l l menta lentities are identical to physical entities , any world th at containsall th e physical entitie s that exist i n our world also contains all

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    the mental entities t hat exist in our world (namely, those mentalent i t ies tha t a re none o ther than var ious ac tua l phys ica lentities). But one can reject numerical mate riali sm withoutrejecting modal materi alism . One can ma in ta in , for example,t h a t although i t would be impossible for th e universe to havebeen ju st th e way t h at i t i s in al l physical respects withou tcontaining all t he phenomenology that it actually contains, still,th is phenomenology is not identical to anythi ng physical. I t isone thing to say th at th e existence of th e physical entities th atactually exist logically necessitates that of the ment al entitiesth at actually exist; it is another (and stronger) thing to say tha tthese physical entities are the mental entities whose existencethey logically necessitate. Modal materialism commits its

    proponents only t o th e former claim; numerical mate riali smcarries a commitment t o the lat ter as well.While numerical materialism is a stronger thesis than modal

    materialism, numerical dualism is a weaker thesis t ha n modaldualism. To prove modal dualism, one must show that it wouldbe possible for everything t o have been exactly as it actually is,physically, but for there not to have existed some mental entityt h a t does actually exist. To th at end, one might argue th at t hephysical facts of our world are logically compatible with thenonexistence of any conscious minds at all; this is th e currentlyinfluential zombie argument for modal d ~ a l i s m . ~ lternatively,one might argue t hat everything could have been t he same as itactually is physically, even if we had had yellow instead of bluevisual phenomenology when gazing at th e clear au tu mn sky. Apossible world in which we are equipped with bodies identicalt o t he ones we actually have, embedded in a physical environ-ment identical to the one that surrounds us, bu t i n which wefail t o have blue phenomenology when looking skyward , wouldbe a world in which there failed to exist some mental entities-various bluish experiences-that actually exist.5

    The possibility of a physical copy of our world contain ing noconscious experience, o r phenomen ally inv erted consciousexper ience, would not only e s tab l i s h modal dua l i sm , bu tnumerical dualism as well. If there is a possible world just likeours physically that fails to contain some actually existingmental entity, then t ha t mental en tity cannot be the sam e asany physical entity. (If i t were, it would exist i n every possibleworld in which t he re exists th e physical entit y t h at i t is.) Butone can consistent ly advocate numerical dual ism withoutendorsing modal dualism. A numerical dualist might agree witha modal mater ialis t t h a t th e physical fact s about our worldlogically necessitate the existence of whatever mental entitiesexist, yet maintain t ha t these entities (o r at least some of them)could exist even in the absence of any physical world. If there isa possible world containing our minds but no bodies, thennothing physical is logically necessary for t he existence of our

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    minds, in which case numerical dualism must be true. But thepossibility of such a world would not support modal dualism,the defining claim of which is t h a t no thing physical is logicallys u f f i c i e n t for th e exi stence of our minds, thoug hts , an dexperiences.

    2. Descartes Position

    S o far we have drawn a dist inct ion between two kinds ofdualism and two corresponding kinds of materialism: numericalmate r ia l i sm , which ent a i l s (but i s not e n ta i led by) modalmaterialism, and numerical dualism , which is entailed by (butdoes not e nt ai l ) modal dua l ism. The quest ions we wan t t o

    consider now is which of these positions Descartes accepts andwhich he rejects.Before we can proceed, however, we need first to consider the

    notion of logical possibility in relation t o Descartes. Descartesfamously claimed tha t God was free to make i t not true t ha t al lth e r ad ii of t he circle a r e equal (AT, 1:152; CSMK, 25)6 andagain t h a t God cannot have been de termined to make it t ruethat contradictories cannot be true together, and therefore . hecould have done the opposite (AT, 4:118; CSMK, 235) . Onecould then infer th at he would also accept th a t it is possible for

    azure to be a shade of yellow or for a million t o be less than two.If one gran ts this, th en arguably he could not have meaning-fully endorsed either modal materialism or modal dualism. In auniverse in which the principle of contradiction does not obtain,the question of whether physical facts do o r do not logicallynecessitate men tal facts (a nd vice ve rsa) can obviously get nogrip.

    This aspect of Descartes thought may prima facie be anobstacle t o our mapping of Descartes dualist position onto thecontemporary positions of modal dualism and modal materi-

    a l i ~ m . ~ e note, however, t ha t Descartes accepts, alongside th isstrong version of possibility engendered by th e divine powers ofthe Cartesian God, a wea ker version of possibility t h a t holdsr e la t ive to human m inds . This latter kind of possibility is whatwe would call logical possibility, and Descartes must accept andapply this notion of possibility in order for the argument of theMeditat ions (and indeed any a rgument) t o get off the ground.

    In the M e d i t a t i o n s , Descartes at te mp ts to found a stablean d lasti ng system of knowledge based upon th e clear an ddistinct perceptions of reason. The reliability of reason, however,mu st minimally r equire t h a t th e principle of contradict ionholds. If this principle did not hold, then we would have toadmit th at reason is unrel iable a nd tha t what is c learly anddistinctly established by reason could be false. For example, ifthi s principle did not hold, we would have t o accept that evenlogically necessary st at em en ts (e.g., 2 + 3 = 5 ) could be false.

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    Reason could get no grip and Descartes project in the M e d i t a -tions must fail.

    Descartes acknowledgment that we as humans must operatewi thi n t he bounds of logical possibility is clearly found, forins tance, in t he Replies to t he Second Set of Objections. There,Descartes deals with the question of whether a clear and distinctperception could be false as follows:

    Now if [the] conviction [from a clear an d distin ct perception] is sof i rm tha t i t is imposs ib le for u s eve r t o have an y r ea son fo rdoubting wh at we ar e convinced of, th en there are no fur ther ques-t i o n s fo r u s t o a s k : w e h a v e e v e r y t h i n g t h a t w e c o u l d r e a s o n a b l yw a n t . W h a t is it t o u s t ha t someone may make ou t t ha t t h e

    perception whose tr ut h we a re so firmly convinced of may appearfalse to God or a n angel, so t h a t it is, absolutely speaking, false?Why should t h i s a l leged absolu te fa l s i ty bother us , s i n c e w enei ther believe in i t nor have even the smallest suspicion of i t?(AT,7:144-45; CSM 2, 103; emphasis added)

    Descar tes mainta in s t ha t th ere i s no point worry ing aboutwhether a claim could be absolutely false for God (as well itmight since God could have willed the principle of contradictionnot to hold). Tr ut h as it obtains for the h um an intellect is allt h a t we could reasonably wa nt (or have), an d we know wehave this when we have a clear an d distinct perception t h at isimpossible t o ever doubt. Descartes thus makes clear here thathum ans can only concern themselves with t r u t h an d falsehoodas they a re established through a hu ma n reason bounded bythe principle of contradiction.

    Again, a little later, when asked about whether Gods natureis possible, he replies:

    If by possible you mea n w ha t everyone commonly means, n amely

    wha tever does not conflict with our h um an concepts, th en it ismanifest th at t he n atu re of God, as I have described it, is possiblein th is sense.. .. Alternatively, you may well be imagi ning someoth er kind of possibil i ty which rel ate s to th e object i tself ; b u tun le s s t h i s ma tches t he first sort of possibility i t can never beknown by t he intellect. (AT, 7:150-51; CSM 2, 107)

    Descartes points out t h a t th e only kind of possibility th a t wehuman s a re acquainted with is whatever does not conflict withour human concepts-that is, with logical possibility. If there isany other kind of possibility, we are incapable of conceiving it,and thus it can never be known by th e intellect.

    In su m, while Descartes a dmi ts a st ro ng version of possi-bility th a t allows azu re to be yellow an d a million to be lessth an two, he also accepts tha t this kind of possibility cannot beknown by th e [human] intellect. Human beings can only think

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    perform only those movements that do not come under thecontrol of th e will. ( Fu rt he r evidence th a t th is i s Descartesview is found in AT, 655 ; CSM 1, 139; and AT, 7:229-31; CSM 2 ,

    Descar tes content ion th a t th e existence of a normal lyfunctioning hu ma n body engaged in characteristically h um anforms of behavior necessitates the existence of a correspondingthinking mind does not, in itself, commit him t o modal materi-alism. As fa r as th e tex tual evidence so fa r brought forwardshows, it may be th a t Descartes would t hi nk t h at th e physicalfacts of our world necessitate the existence of thinking mindsbut not the existence of sensations, raw feels, or qualia. Sincethes e minds and th eir thou ghts ar e not, on Descartes view,

    physical, his claim that their existence is logically entailed byvarious physical facts about us is already a striking departurefrom mainstream dualism. All th e same, Descartes is not a full-fledged modal material ist unless he would accept th at all mentalphenom ena, including sensory phenomenology, a re a logicallynecessary consequence of the worlds physical arrangement.

    161-62.)

    In the Sixth Meditation, Descartes remarks that

    Nature teaches me, by these sensations of pain, hunger, thirst ands o on, th a t I am not merely present in my body a s a sai lor is

    present in a ship, but t ha t I am very closely joined and , as it were,intermingled with i t , so t h a t I and the body form a unit. If thiswere not so, I, who am nothing but a thinking thing, would not feelpain when the body was hurt, but would perceive the damage purelyby th e intellect, jus t a s a sailor perceives by sight if anything in hi ssh ip is broke n. Similarly, when th e body needed food or d rin k, Ishould have an explicit unders tand ing of the fact, inst ead of havingconfused sensa tions of hunge r an d th irs t. For the se s ensations ofhunger, thirst, pain and so on are nothing but confused modes ofthin king which ari se from th e union a nd , as i t were, intermingling

    of the mind with the body. (AT, 7331; CSM 2, 56)

    Descartes claim th a t he might have perceived th e damage t ohis body purely by the intellect may give th e impression th a t hethinks his body might have exhibited all the changes that itactually does, even in the absence of sensations of pain, hunger,thirs t , and so on. But in fact Descartes leaves it open th at t hebehavior of his body would be different from what i t actually is,if he perceived damage to it purely intellectually, rather than ashe actually does (i.e., by having painful sensations). Furthermore,as we have seen , Desc artes holds t h a t h is body necessarilywould move differently from how it actually does if it were notconnected t o a thinking, willing mind. So, in order to conceive ofa situation in which hi s body does everyth ing it actually does,he must conceive of it as connected with such a mind. But givent h a t i t is so connected, sensations cannot help but result, fo r

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    these sensations of hunger, thirs t, pain and so on ar e nothingbut confused modes of thinking which arise from the union and,as i t were, intermingling of th e mind with the body.

    I t would be a problem for our interpretation if Descartesst at ed th at bodies could be made t o behave exactly as theyactually do by minds that were present in them as a sailor ispresent in a ship, rat he r t han by being with the bodies. I t wouldalso go against our in ter pre tat io n if Descartes were found toclaim that his body could have been manipulated marionette-wise by God o r an angel to move in al l th e ways i t actual lymoves, without corresponding sensations. If Descartes held sucha view, he would have to be counted a modal dualist, although apeculiar one for whom the physical facts of our world logically

    necessitate the existence of nonphysical minds, thoughts, andacts of will, but not that of sensory phenomenology.However, there is good evidence t hat Descartes does not take

    th is position. For example, he gives th e following account ofsense perception and imagination to Frans Burman.

    When exter nal objects act on my senses, they pri nt on the m a nidea, or ra the r a figure of themselves. And wh en th e mind a tt en dsto these images printed on [the pineal gland] in thi s way it is saidto have sen se perception. When, on th e other h and , the images on

    th e gland ar e imprinted not by external objects but th e mind itself,which fash ions and shapes them in th e bra in in t he absence ofexternal objects, th en we have imagination. The difference betweensense perception an d imagination is real ly just this, th at in sensepe rcep t ion the images a r e impr in t ed on the b ra in by ex t e rn a lobjects which ar e actually present, while in th e case of imaginationth e images a re imprinted by t he mind without any extern al objects,an d with th e windows shu t, as it were. (AT, 5162; CSMK, 344-45)

    For Descar tes , then , phenomenal s ta te s of sens a t ion an d

    imagina tion a r e s t a t e s the mind i s in when i t a t t en ds tophysical images in t he brain. The question th at concerns us iswhether it is Descartes view t h a t precisely these phenomenalstates must arise when the mind attends t o the neural images.

    At first glance , i t may seem tha t th is is not his view.Descartes holds that a particular sensation in our minds alwayscorresponds t o a particular (kind of) figure o r image in the pinealgland because t his correspondence i s natur ally instit uted byGod. He also seems to allow that God could have instituted agiven s t at e of th e body to correspond to a different sensation.For example, in discussing t he pain-in-the-foot sensation th atcorresponds t o a particular s tat e of the pineal gland, he writes:

    I t is t r ue t ha t God could have made th e natu re of man suc h th atthis p articular motion in th e brain indicated something else to themind; it migh t fo r example , have made t he mind aware of t h e

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    actual motion occurring in t he brain, or in th e foot, or in a ny of theinterm ediate regions; or i t might have indicated somethi ng elseentirely. (AT, 7:88; CSM 2, 60-61)

    Given that Descartes is prepared to accept that God could haveins t i tu ted tha t a particular motion in t he brain ( o r more pre-cisely, t he pineal gland) could have corresponded t o a differentphenomenal experience, i t might seem th at he would be all t hemore prepared to accept th at t he particular motion th at nowcorresponds t o , say, a sensation of red could have been insti-tuted by God t o correspond to a violet sensation.

    However, a closer look at the larger textual context ofDescartes discussion about the pain-in-the-foot sensation shows

    th at Descar tes would have to ru le out th a t i t i s logical lypossible for God to institute any other correspondence betweensensat ions and pineal gland s tat es than th e ones already soinstituted. Descartes makes clear in the Meditations th at Godwhom he clearly and distinctly perceives to exist cannot, onpain of contradiction, be other than all-good and nondeceiving:

    By G od I mean th e very being th e idea of whom is within me, th atis, the possessor of all t he perfections .... I t is clear enough fromth i s t ha t he canno t be a deceiver, sinc e i t is manifes t by th e

    na tu ra l light t ha t all fra ud an d deception depend on some defect.(AT, 75 2; CSM 2 , 35)

    I t i s i n t he very conception of God t h a t God mu st be whollyperfect-therefore, he cannot be a deceiver or other th an whollygood. Thus, while Descartes is prepared t o admit, for th e sake ofargu ment , th e hypothesis t ha t God might have inst i tute d adifferent sensation to correspond to a particular brain s tate, healso makes clear that this would be logically impossible giventhe divine at tributes of omnipotence and goodness.

    My ... observation is th at any given movement occurring in th epa rt of the brain th at immediately affects the mind produces ju stone corresponding sensation; a nd hence the best system that couldbe devised is that i t should produce the one sensation which, of allpossible sensations, is most especially and most frequently conduciveto the preservation of the healthy man. And experience shows thatth e sensations which na tu re ha s given us ar e all of this kind; an dso there is absolutely nothing to be found in th em t ha t does notbear witness to the power and goodness of God. (AT, 7:87; CSM 2,60; emphasis added)

    Descartes makes it clear t ha t t he actual system institu tedby God for linking specific sensations and particular brainstates is the best system, th e one tha t is most conducive to thepreservation of humankind. The sensation t h a t God ha s linked

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    to a particular pineal gland st at e is, Descartes states, the onesensa tion, of all p o s s i b l e sensations, th at is most conducive t ot he p rese rva t ion of the human being. Moreover, the othersensat ions t ha t we possess a re all of th is kind. God thus couldnot, without contradicting his own natu re as all-good, instituteany other system th a n t he one we already have. I t follows t h a tDescartes would not accept that a system involving, for example,inverted phenomenal spectra could ever be instantiated.

    Descartes would thus not have accepted modal dualism. Onthe contrary, for him, the physical universe could not have beenth e same without containing all the minds an d mental state s,events, etc., t h a t i t actually contains. For him, th e existence ofour minds, thoughts, and phenomenal experiences would be a

    logically inevitable consequence of the structure, function, andbehavior of ou r bodies. He would t h us h ave accepted modalmaterialism. But he is not a numerical materialist. Descartesrepeatedly main tains t h a t minds can exist without t he benefitof bodies. I n t he Second Medi tati on, he goes s o f a r as toentertain a situat ion in which his mind exists in th e absence ofany physical world a t all . If such a s i tua t ion is logicallypossible-and it appears th a t Descartes thinks it is-the mindcannot be one and t he same thing as the body, for if it were, anysit ua tio n in which t h e body failed to exi st would be one in

    which the mind failed to exist as well. Descartes philosophy ofmind therefore defies simple classification as dua l i s t o rmaterialist: his view is a combination of modal materialism andnumerical dualism.

    We now consider two objections t o classifying Descartes as amodal materialist. The first is based on Descartes physics; thesecond, on some comments Desc artes make s in th e Fo urt hReplies.

    2.1 Descartes Deterministic Physics

    Descartes physics holds to the principle of the conservation ofmotion and, moreover, main tains th at ma tte r can only be set inmotion by the im pact of oth er moving m a tt e r according to aspecific set of physical laws. Descartes physical world thusappe ars to be a closed system where every physical state ofaffairs is determined by some previous physical state of affairs.Thi s being th e case, th e occurrence o r not of mental eventswould seem incapable of making any difference at th e physicallevel: the physical history of the world might have proceededj u s t t h e s a m e as i t ac tua lly has , even if human s a nd o the rcreatures had lacked minds entirely.

    The tension between Descartes physics and his view thatth e presence of th e menta l somehow bears on th e behavior ofthe physical forms a known crux in Descartes thought. If everyphysical event has a completely determining physical cause,

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    then ther e ar e only two ways in which me ntal events can havephysical effects. Eithe r (1) mental events must be a species ofphysical events o r (2 ) th e physical effects of menta l events mustbe causally overdetermined (by the physical and m ental eventstha t separa tely cause them) . Since Descartes clearly rejects (11,it appears he must regard a significant amount of human bodilybehavior as systematically overdetermined by distinct mentalan d physical causes-an unp rep osse ssin g, even if logicallyconsistent, view.8

    However, it is not clear t ha t Descartes physics is completelydeterm inist ic . Leibniz, f o r example, argued t h a t Descartesclaim th a t m at te r can only be se t in motion by th e impact ofother moving matter does not rule out that the direction of the

    movement may be dependent on fac ts th a t a re no np h y ~ i c a l . ~Desc artes pr inciple of th e conse rvat ion of m at te r can bepreserved, without a ssuming t h a t every physical event ha s acomplete physical cause, and without precluding nonr edundantmen tal cause s for some physical events. More recently, Garbe rhas argued that Descartes principle of conservation does notrule out th a t matt er can be set in motion by factors other th a nthe impac t of other moving mat te r (such as God or men talsubs ta nces) . More par t icu lar ly, he poin ts t o Descar tes Principles , in which his specif icat ion of the conservat ionprinciple, a s well as of his third law of impact, evidently leavesroom for physical changes to be brought about by finite humanminds.1

    Alternatively, i t may be t h a t Descartes does not hold t h a tmen tal events have physical effects at all. Secada argues t h a tDesca rtes is a n occasionalis t for whom th er e is no genuinecausation of empirical e ven ts by empirical events , not even ofphysical ev ent s by oth er physical events . On th is view, th ecausa l closure of th e physical is closure only under a n ersatz orderivative causality, and t h e coordination of mind a nd bodycomes of mental and physical phenomena having a commonorigin in th e t rue causa tion of divine will. Loosely speaking, wemay describe mental events as having physical effects, but wemust take care to avoid the uneducated error of assuming tha ta me nt al event-or an y emp iric al event-has th e power tocreate subs equent physical eve nts (AT, 7:49; CSM 2, 33; AT,7:78-79; CSM 2, 54-55). Empirical events cause other empiricalevents only in the sen se th a t empir ical even ts occur with acer tai n diachronic regular ity-a regula r i ty th a t is not self-propagating but results from the orderly manner in which Godsynchronically causes successive s ta te s of the world.

    Whether interactionist or occasionalist, one thing i s certain:f o r Descar tes , th e ex is tence and ac t iv i ty of minds i s not acontingent, bu t a necessary, prer eq uis ite of cer ta in forms ofphysical behavior. Thus, if he is a n interactionist who r egar dsmental events a s having physical effects, he m ust t ak e these

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    effects to be ones th at logically require for their occurrence - theoccurrence of the corresponding mental events. Similarly, ifDescartes is a n occasionalist, he m ust hold t h a t God cannotpossibly will certain forms of physical behavior to t ak e placewithout willing the occurrence of the corresponding mentalevents; at lea st, t hi s mu st be Descartes view insofar as heconfines his attention t o possibilities t ha t a re within th e realmof human comprehension.

    2.2 Descartes Comments in the Fourth Replies

    In his reply to Arnaulds Fourth Set of Objections, Descartesmakes claims such as th e following:

    a body can be understood distinctly as a complete thing, withoutany of th e a ttributes which belong to the mind (CSM 2, 157)

    and

    I understand a thinki ng substance to be ju st as much a completething as an extended substance. (CSM 2, 157)

    Such claims might be int erp ret ed as showing t h a t Descartes

    thought t ha t th e mental an d material a re complete an d inde-pend ent real ms, whose variou s operat ions proceed whollyindependently of each other. In that case, he would accept thati t is possible that a body (qua complete thing) could exist as i tdoes even if th er e were no minds-and, similarly, t h a t a mind(qua complete thing) could exist in th e way it does even if bodydid not exist.

    Whether one can ultimately make cogent sense of Descartesclaims in this portion of the Fourth Replies about complete andincomplete things is far from clear.12 But the claims as they standcertainly do not support the contention that Descartes was amodal dualist. Descartes specifies earlier in the Fourth Repliesth at he means by a complete th ing a substance endowed withth e forms o r attr ibutes which enable me t o recognize th at it is asubstance (AT, 7:222; CSM 2, 156). In th e Sixth Meditation, heclaims tha t, in recognizing th at th e body ha s t he attributes ofbeing extended and nonthink ing, while he himself ( q u amind) ha s t he a t t r ibu tes of thought an d nonextension, herecognizes th at h e is really distinct from his body, and tha t h e( qua thi nke r) an d hi s body ar e distinct substances (AT, 7:78;CSM 2,54). This being the case, the mind can, at least throughthe power of God, exist without the body; and similarly the bodycan exist without th e mind (AT, 7:170; CSM 2, 119).

    However, while Descartes thinks that the body can existwithout th e mind, it does not follow tha t he thi nks th at a bodyth at exists without a mind would behave i n exactly th e same

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    way as a body th a t ex ists connected wi th a mind, an y moreth an his claim th at minds can exist without bodies implies th a tminds that exist in a universe without bodies would haveexperiences entirely identical to minds th at , like our own, areconnected to bodies. With respect to the latter claim, writerslike Cottingham have made clear th a t Descartes holds th a t it isonly minds t h a t ar e connected to bodies t h a t have sensoryperception and imagination. In contrast, the utterly disembodiedCartesian mind would possess free will and the ability torat i ocin ate bu t would have no aw aren ess of color, ta st e or~me11. l~ nd, as we have seen, th er e is ample textua l evidenceth at , in Descartes view, bodies in a u niverse witho ut mindswould not exhibit the same movements and changes as bodies

    in a universe like ours where minds do exist.In c la iming th a t minds an d bodies a re complete th ings ,Descartes is indeed maintaining t h at they a re substances th atcan exist ap ar t from each other-that it is possible for there t obe a universe with mind and no body, and one in which there isbody but no mind. But this does not thereby commit him to theclaim th at in a universe with bodies and no minds, bodies couldbehave in exactly the same way as th ey would in a universewith bodies connected to minds. In parti cula r, it does notcommit him to th e modal dua lis t claim (which he elsewhereexplicitly rejects) t h a t i t is possible for th er e t o be a mindlessuniverse containing bodies th a t move in all th e ways hu ma nbodies actually move.

    3. Conclusion

    We have argued that Descartes philosophy of mind is definedby two theses: one t h a t rejects t he identity theory of mind andbody, and another t h at is tant amou nt to materialism, as t h a tposition i s now commonly understood. For Descartes, the worldsphysical na tu re logically necessitates t h at th er e ar e preciselythose minds, thoughts, a nd conscious experiences t h a t actuallyexist. Yet these minds are not themselves physical and could, intheory, exi st in th e absence of an y physical world. I t see msappropr iate to call this pair of theses Cartesian dualism.

    Why Descartes held this view, and modal materialism inparticular, is not a t all obvious. Presumably he was alive to thepossibility of arguing against modal mat erial ism along th esame l ines a s he a rgues aga in s t numerica l ma te r i a l i sm; i twould simply be a matter of arguing for the possibility of (fullyoperational) bodies without minds ra th er t ha n minds without(fully operational) bodies; thi s is, in effect, how Leibniz argu esfor modal dualism.14There is some evidence that Descartes maythi nk th a t modal dualism does not allow for a relation of mindand body intimate enough to comport with our exercise of freewill (AT, 7:18-19; CSM 1, 205 in conjunction with AT, 7:84; CSM

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    2, 58). There is also some evidence th at Descartes th in ks th atthe actual physical world is the only physical world possible-he certainly held that all possible physical states are actualized

    (AT, 8A:103 ; CSM 1, 258)-in which case modal materi alis mwould be trivially true.But the attempt t o account for Descartes embrace of modal

    mate riali sm mu st be th e subject of anot her paper. Wha t wehope to have shown here is t h a t Descartes, while acceptingnumerical dualism, also comes out as a modal material is t .Contemporary philosophers who a re tempted to assume t h a tDescartes is a direct ancestor of the most prevalent currentversions of dualism neglect th e continental drift in conceptionsof dual i sm th a t ha s ta ke n p lace be tween h is t ime and our

    0 ~ n . l ~

    Notes

    Some commentators suggest th at Descartes may not even havebeen a numerical dualis t ; see, e.g. , Clark e Desmond, DescartessTheory of Mind (Oxford: Oxford University Press, 2003). It is beyondth e scope of this pa per to en te r into a detailed discussion of suchviews. We hope th a t th e te xtua l evidence provided in th is paper willsuffice to show that Descartes is a numerical dualist, as indeed manycommentators would accept. Furt he r discussion of the points raised byClarke must await a further occasion.

    For t he phenomenaUpsychologica1 distinction, see Thomas Nagel,What Is It Like to Be a Bat? Phi losophica l Review 83, no. 4 (1974):435-50; Ned Block, On a Confusion about a Function of Consciousness,B e h a v io r a l a n d B r a i n S c ie n c e s 18, no. 2 (1995): 227-87; David J.Chalmers, T h e C o n s c io u s M i n d : I n S e a r c h of a F u n d a m e n t a l T h e o r y(Oxford: Oxford University Press, 19961, 3-31.

    See, for example, David Lewis, An Arg umen t for th e Ide nti tyTheory, Journal of Phi losophy 63, no. 1 (1966): 17-25; Chalmers, T h eC o n sc io u s M i n d , 38-41; Fra nk Jackson, From M etaphys i cs to Eth ic s :

    A Defense o f Conceptual An alysis (New York: Oxford University Press,See Keith Campbell, B o d y a n d M i n d (London: Macmillan, 19701,

    100-109; Robert Kirk, Se ntienc e and Behavior, M i n d 83, no. 329(1974): 43-60; Chalmers, The Conscious Min d , 94-99.

    For discussion of this inverted spectrum argume nt, see Jo hnLocke, A n E s s a y C o n c er n in g H u m a n U n d e r s t a n d i n g , ed. Peter H .Nidditch (Oxford: Clarendon Press, 19791, II.xxxii.15; Ludwig Wittgen-stein, Phi losoph ica l Inves t iga t ions , 3r d ed. (New York: Macmillan,1958), Sec. 272; an d Sydney Shoemaker, The Inverte d Sp ectrum ,Journal of Phi losophy 79, no. 2 (1982): 357-81.

    Quotations ar e from Th e Ph i lo soph ica l W r i t i n gs o f Desca r t e s ,Vols. 1, 2 , a nd 3 t ra ns. John Cott ingham, Robert Stootfhoff, an dDugald Murdoch (Vols. 1 and 2) together with Anthony Kenny (Vol. 3)(Cambridge: Cambridge Universi ty Press, 1985, 1984, and 1991), citedrespectively as CSM 1, CSM 2, an d CSMK. Reference is also made toAdam a nd Tannerys Oeuvres de D escar tes , Vols. 1-12 (Paris: J. Vrin,19831, cited as AT, followed by the relevant volume and page number.

    19981, 9-14.

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    See Ha rry Fr ankf urt, Descartes on th e Creation of the Etern alTruths, Phi losophica l Review 86, no. 1 (19 77): 36-57; E. M . Curley,Desca r t es on th e Crea t ion of t h e E te r na l Tru ths , P h i l o s o p h i c a lRev iew 93, no. 4 (198 4): 569-97; an d Jo na tha n Bennett, DescartessTheory of Modality, Philosophical Review 103, no. 4 (1994): 639-67.

    This view h as been defended by, for examp le, Eug ene Mil ls, In te rac t ion is m and Overde termina t ion , A m e r i c a n P h i lo s o p hi c a lQuarter ly 33 (1996): 105-17.

    See Gottfried Leibnizs le tt er To Arnauld (April 30, 16871, i nPhilosophical Essays, ed. Roger Ariew a nd Daniel Garb er (Indianapo lis:Hackett, 19891, 81-90, an d The Pr inciples of Philosophy, Sec. 80 ofLeibnizs Monadology in Philosophical Essays, 213-15.

    l o See Daniel Garber, Desca r t e s Me taphys i ca l Phys i c s (Chicago:University of Chicago Press, 19921, 303.

    l 1 See Jo rge Secada , C a r t e s i a n M e t a p h y s i c s : T h e S c h o l a s t i cO r i g i n s of M o d e r n P h i l o s o p h y (Cambridge: Cambridge Univ ersi tyPress, ZOOO), 105-07.

    l 2 See, e .g. , Bernard Wil l iams, D e s c a rt e s: T h e P r o j e c t of P u r eE n q u i r y (Harmondsworth: Penguin, 197 8), 111-14; Anthony Kenny,Descartes: A S t u d y of H is P h i lo sophy (New York: Gar lan d, 19871, 86-95.

    l 3 See Joh n Cot t ingham, Car tes ian Tr ia l i sm, M i n d 94, no . 374(1985): 218-30.

    l4 In Sec. 17 of t he Monadology, in Philosophical Essays, ed. RogerAriew an d Daniel Gar ber (Indianapo lis: Hackett, 19891, 215.

    l5 This ap t metaphor is borrowed from Gordon Bak er and K ather ineJ. Morr is , D e s c a r t e s D u a l i s m (London and New York: Routledge,1996), 148.

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