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Preferred Citation: Horst, Steven W. Symbols, Computation, and Intentionality: A Critique of the Computational Theory ofMind. Berkeley: University of California Press, c1996 1996. http:ark.cdli!.or"ark:1#$#$ft%$9n!#6&

Symbols, Computation, and Intentionality

A Critique of the Computational Theory of Mind

Steven W. Horst

UNIVERSITY ! C"#I!RNI" $RESS

Berkeley Los Angeles Oxford

% &''( T)e Re*ents o+ t)e University o+ Cali+ornia

'or (y parents, Willia( and )rin Horst

Preferred Citation: Horst, Steven W. Symbols, Computation, and Intentionality: A Critique of the Computational Theory ofMind. Berkeley: University of California Press, c1996 1996. http:ark.cdli!.or"ark:1#$#$ft%$9n!#6&

'or (y parents, Willia( and )rin Horst

$RE!"CE

*his !ook +as a lon" ti(e in the (akin". *here are parts of it that date !ack to a!ot 19&- and otherparts that are very recent indeed. t started ot as an atte(pt to !rin" (y o+n pecliar philosophical!ack"rond /+hich is an nsal one in co"nitive science circles0 into contact +ith +hat +as at thatti(e /and to so(e etent still is0 the (ainline vie+ of the (ind in analytic philosophy of (ind: theCo(ptational *heory of 2ind /C*2 for short0. ca(e to the stdy of co"nitive science +ith threekinds of relevant !ack"rond, each of +hich is at least a little !it off center +ith respect to theconte(porary scene in the philosophy of (ind. Perhaps the (ost prosaic of these is that +orked (chof (y +ay thro"h "radate school teachin" corses in co(pter pro"ra((in", soft+are desi"n, andartificial intelli"ence. t +old !e a (ost heinos ea""eration if +ere to descri!e (yself as either aco(pter scientist or a hacker, !t learned so(e theory, did so(e pro"ra((in", and (ade (y +aythro"h (ost of the three3vol(eHistory of Artificial Intelligence+ith a class of nder"radatestdents. kne+ co(pters in theory and in practice !efore !e"an to think a!ot the( as aphilosopher.

*his, ho+ever, +as not (y first eposre to co(pter (odels of the (ind. had stdied as an


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nder"radate +ith Stephen 4ross!er" of Boston University, one of the fe+ people doin" continos+ork in neral net+ork (odels fro( the 196$s p ntil the present, even thro"h the t+o decades +henit +as not a particlarly poplar thin" to !e doin". So +hereas (ost people in the philosophy ofco"nitive science ca(e to co"nitive science !y +ay of the sy(!ol3processin" paradi"( e(!racin"

5 vi 5*rin", 2insky, e+ell, Col!y, Wino"rad, and 2arr /to na(e !t a fe+0, ct (y teeth on neralnet+ork (odels. n a +ay, have !een in eactly the opposite position of (ost philosophers doin"co"nitive science in recent years: +hereas they have had to learn a!ot the 7ne+7 neral net+orkparadi"( /+hich is in fact as old as the sy(!ol3processin" paradi"(0, had to do eactly the oppositein the late 19&$s.

*he third ele(ent in (y !ack"rond, of corse, +as (y philosophical trainin". 2y first philosophicallove +as speech act theory, on +hich +rote an nder"radate thesis in 19&1 +ith Brce 'raser. *he(a8or philosophical +riters on the s!8ect at that 8nctre +ere 4rice, stin, Stra+son, endler,Searle, Bach, and Harnish. With the possi!le eception of the last t+o, these philosophers practicedtheir trade in a style (arkedly different fro( that co((only fond in co"nitive science today. t thesa(e ti(e, +as !e"innin" to read so(e of the +orks of )d(nd Hsserl, +hich +as to have aprofond inflence on ho+ ca(e to vie+ philosophy. n spite of praise fro( people like Chishol(,Sellars, ;reyfs, 'o"ical nvesti"ation,7 and no one +as (orekeenly a+are than he of the difficlties and pitfalls of co(in" to a philosophical nderstandin" of the(ind. Hsserl?s focs on the centrality of intentionality (ade +hat see(s to have !een a per(anenti(pression on (e. So(e+here in 19&@ !eca(e convinced that the stdy of speech acts cold notpro"ress frther +ithot a stdy of intentionality. /t +as "ratifyin" to see a year later that Aohn Searlehad co(e to a si(ilar conclsion.0 *hat focs !eca(e central to (y philosophical thinkin" for the netten years, and it still occpies an i(portant /tho"h no lon"er central0 place for (e in the sche(e ofi(portant philosophical pro!le(s.

s a "radate stdent, +orked +ith enneth Sayre at otre ;a(e, one of the first philosophers to+rite a!ot artificial intelli"ence in the early 196$s, and a lon"ti(e proponent of an alternative visionof the (ind centerin" arond the 2athe(atical *heory of Co((nication articlated !y Shannon andWeaver. t +as, in fact, only after started +orkin" +ith Sayre that !e"an to read +hat (ost peopleconsider 7(ainstrea(7 artificial intelli"ence and philosophy of co"nitive science, so the sy(!ol3processin" paradi"( +as actally the thirdparadi"( +as eposed to in co"nitive science. lon" the+ay in (y philosophical stdies felt so(e inflence fro( the +ritin"s of Plato, ristotle, ant, andWitt"enstein.

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n short, ca(e to the conte(porary scene in co"nitive science +ith a very different list ofphilosophical and scientific heroes fro( those of (ost of (y collea"es in the field and (ch of +hat fond in the 7(ainstrea(7 initially strck (e as e(inently +ron"headed. Bt it is one thin" to thinthat so(ethin" is +ron"headed it is of corse =ite another to nderstand +hy people +old !elieve itand to identify 8st +here yo think the pro!le( lies. *his !ook is in lar"e (easre the prodct of alon" process of tryin" to do t+o thin"s: first, to nderstand the pro8ect fro( the inside, as it +ere, inter(s that its o+n advocates +old e(!race and, second, to articlate +hat see( to (e its (a8or fla+s


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in a fashion that does not depend too (ch pon an alternative philosophical vie+point and +hich(i"ht !e accessi!le to so(eone +ho does not share (y o+n philosophical leanin"s.

s a reslt, the first t+o chapters of this !ook atte(pt to lay ot co(ptationalis( in its historicalcontet and to eplain to the reader +hy one (i"ht very sensi!ly think that it is offerin" so(e te(ptin"philosophical frit. t the sa(e ti(e, have tried to e(phasiDe ele(ents in the historical contet andconnections +ith other strands of philosophical psycholo"y that see( i(portant yet are often passed

over !y those +ho consider the(selves to !e +ithin the co(ptationalist ca(p. hope that thesechapters +ill serve as a "ood introdction to the co(ptational theory for a +ide philosophicaladience. sspect that they (ay also prove sefl for the initiate +ho +ishes to read the criticalsections of the !ook, as they atte(pt to lay ot co(ptationalis( +ith (ore eactitde than is nor(allydone and +ith a (ini(( of rhetoric. n a sense, the (oral of the !ook is 8st this: if yo are notetre(ely carefl a!ot ho+ yo se +ords like ?co(pter?, ?sy(!ol?, ?synta?, and ?(eanin"?, yo arelikely to st(!le into so(e pernicios confsions a!ot co(ptation and the (ind and to !e te(pted!y so(e s!tly fallacios ar"(ents that see( to deliver philosophical reslts !t in fact (islead.

*he rest of the !ook "re+ "radally. t started as a prely critical pro8ect of de!nkin" clai(s that C*2provides an accont of the intentionality of the (ental and a 7vindication7 of realis( a!ot (entalstates. Ence had satisfied (yself that had proven (y case there to (y o+n satisfaction, !e"an to !e(ore interested in +hat cold !e said in a positive +ay a!ot the i(portance of co(ptationalpsycholo"y as a +ay of nderstandin" the (ind, and ho+ far a+ay fro( the vie+s articlated !y+riters like Aerry 'odor and Fenon Pylyshyn one +old have to "o in order to do so. Unlike so(ecritics of C*2, do not!elieve that e(pirical research in co"nitive science stands or falls +ith thephilo!

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sophicalclai(s of C*2. *he several chapters of the !ook that eplore alternative +ays of lookin" atco(ptation and the (ind +ere first drafted at the ational )ndo+(ent for the H(anities S((er

Se(inar on 2ental Gepresentation held at the University of riDona in the S((er of 1991. Go!C((ins, +ho directed that institte, has "one far !eyond the call of dty !y readin" three separatedrafts of the !ook in the three years since that ti(e. Chapter 6, +hich contains so(e of the (ostprovocative (aterial in the entire !ook, +as +ritten after the rest of the (anscript to respond tocriticis(s that Go! raised a!ot an earlier draft. Go! has (y ndyin" "ratitde for his responses alon"the +ay, and not least of all for occasionally ad(ittin" that had convinced hi( a!ot so(ethin".*hanks to hi( and to the )H, +hich helped finance that etre(ely prodctive s((er.

2a8or thanks also "o to en Sayre, +ho forced (e to take C*2 seriosly and on its o+n ter(s, andforced (e to a hi"her standard of clarity and eactitde than (i"ht other+ise have attained. *hanks toen also for the sefl +ay he en"a"ed in the process of helpin" (e ha((er ot vie+s that +erestron"ly related to his o+n yet contrary to his o+n for(lations.

Aay 4arfield of Ha(pshire Colle"e read and co((ented pon the entire (anscript very late in the"a(e, (ade so(e very spportive co((ents, and also (ade a n(!er of very i(portant s""estionsthat have lti(ately (ade the final prodct a (ch !etter and (ore reada!le !ook than it other+ise(i"ht have !een. *he chapter on natraliDation in particlar is (ch epanded as a reslt of Aay?s/deservedly0 pitiless attack pon a for(er incarnation of the sa(e. / fear it still does not (eet +ith hisentire approvalthe credit for its epansion is his, any residal falts are (y o+n.0

Gichard ;eWitt of 'airfield University also +ent !eyond the call of dty in readin" (ltiple drafts offor or five chapters, and has !een spportive of the pro8ect via n(eros e3(ail echan"es since +e


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(et at C((ins?s )H se(inar. >ike+ise, (y Wesleyan collea"e Sanford Shieh (ade so(e veryhelpfl s""estions on the chapters in Part , and pro!a!ly saved (e fro( so(e "rave e(!arrass(entsin (y se of ter(s that had technical (eanin"s in lo"ic of +hich +as !lessedly na+are.

2any other people read or co((ented on all of part of the (anscript alon" the +ay. ll of thefollo+in" people +ere at least so kind as to a"ree to read parts of the (anscript for (e so(e+herealon" the line. 2any (ade i(portant contri!tions to the present for( of the +ork !y their co((ents

and criticis(s: 2ichael nderson, Go!ert di, >ynne

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Gdder Baker, ;avid Brrell, H!ert ;reyfs, aron )didin, Brian 'ay, *i( 'ischer, Pat 'ranken,Brce 'raser, Heather 4ert, Gth 4inD!er", ictor 4orevitch, Go!ert >osonsky, a"hn 2ci(,Chris 2enDel, 2ark 2oes, Hans 2Iller, Shelly Park, Bill Ga(sey, Bill Go!inson, and Aoe Gose.

'inally, shold like to thank the (any people +hose love and friendship over the years have (ade itpossi!le for (e to prse so(ethin" as de(andin" as a !ook in philosophy. n particlar, +ish tothank (y parents, +ho have provided a(ple spport thro"hot (y life, and +ho have !een in (y

corner for (any years +hile +orked on a pro8ect +hose (erits they cold only take on faith. Platoso(e+here descri!es intellectal creations as a kind of pro"eny. hope that they +ill !e pleased +iththeir first "randchild.

2;;>)*EW, CE)C*CU*EC*EB)G 199J

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INTRUCTIN

*here are fe+ thin"s that hold a "reater fascination for s h(an !ein"s than the pro8ect of eplainin"orselves to orselves. En the one hand, the h(an (ind is the part of s that (akes s +ho +e are asindividals. t is also or (inds that set s as a species apart fro( !rte (atter and fro( other (e(!ersof the ani(al kin"do(. *he centrality of self3kno+led"e in Western philosophy "oes !ack at least toSocrates? adherence to the (otto inscri!ed over the te(ple of pollo at ;elphi: 7no+ thyself.7 En theother hand, the (ind has proved one of the (ost intracta!le (ysteries for (odern science. ndeed,(odern science, conceived as a discipline concerned +ith the la+fl casal interactions of (aterial!odies, has !een hard pressed to acco((odate the +orld of tho"hts and concepts and i(a"es thatsee( essential to any treat(ent of the (ind. Ene (i"ht even "o so far as to say that the centralproblem of modern philosophyhas !een one of so(eho+ closin" the "ap !et+een t+o apparentlyinco((ensra!le discorses: a discorse a!ot or (inds that speaks of ideas and i(a"es, and adiscorse a!ot the +orld of natre that speaks of casal relations !et+een !odies in (otion.

Since lan *rin"?s introdction of the notion of a co(ptin" (achine in the late 19#$s, there has !eena "ro+in" interest in a ne+ paradi"( for nderstandin" the (ind: a paradi"( that treats the (ind as adi"ital co(pter. *he arrival of (achine co(ptation pon or intellectal landscape has had aprofond and +idespread i(pact pon research in the (any disciplines that are concerned +ith thestdy of the (ind. n fields sch as co"nitive psycholo"y, etholo"y, lin"istics, the philosophy


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of (ind, and co"nitive neroscience, the co(ptational vie+ of the (ind has !eco(e a (ainstrea(vie+perhaps even the do(inant vie+ in recent years. )ven tho"h there is no (onolithic consenssa!ot ho+ the co(pter paradi"( is to !e applied to the (ind, and even tho"h there are (anyresearchers in all of the disciplines that stdy the (ind +ho are +orkin" ot of other traditions, it is !yno+ "enerally a"reed that the co(ptational approach has e(er"ed as a force to !e reckoned +ith. nd

ths even +riters +ho vie+ the co(pter (etaphor as essentially !ankrpt have nonetheless felt (ovedto devote considera!le ink to reftin" it or esta!lishin" the (erits of their o+n vie+s a"ainst it.

!elieve that there are t+o very different approaches that a philosopher (ay take to this very rich !odyof 7co(ptationalist7 +ork in the stdy of co"nition or 7co"nitive science.7 *he first is that of thehistorian and philosopher of science. s a philosopher of science, one (ay look at the co(ptationalistparadi"( in psycholo"y +ith an eye to+ards issues that are internal to the "arious sciences ofcognition:What are the (ethodolo"ical ass(ptions of co(ptational psycholo"yK Ho+ do they differfro( those of, say, !ehavioris( or associationis( or neroscienceK What are psycholo"ical theoristsreally co((itted to in their se of theoretical ter(s sch as ?representation? or ?synta?K What are theisses that really stand !et+een rival research pro"ra((es sch as 7"ood old3fashioned ,7 +hiche(phasiDes rles and representations, and neral net+ork approachesK What are the i(plicitass(ptions of different theorists a!ot the 7"ood3(akin"7 =alities of scientific theories in a do(ainsch as psycholo"yK

En the other hand, the philosopher of mind(ay also look to the co(ptational paradi"( for ans+ers tolon"3standin"philosophicalpro!le(s, sch as the (ind3!ody pro!le(, isses a!ot the (etaphysicalnatre of the (ind and the relationship !et+een tho"ht and (atter, the relationship !et+eenpsycholo"y and the natral sciences, and the natre of intentionality. While there have !een so(e+elco(e contri!tions of late to the history and philosophy of psycholo"y that take a carefl look atactal research in the sciences of co"nition,L1M !y far the "reater portion of philosophical interest in theco(pter paradi"( has !een concentrated on the (ore distinctively philosophical enterprises ofeplainin" intentionality and 7natraliDin"7 psycholo"y !y renderin" its co((it(ent to (ental states

and processes co(pati!le +ith (aterialis( and the "enerality of physics.*his !ook is intended as a contri!tion to+ards sch an nderstandin" of the natre of the co(pterparadi"( and its i(portance to the

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e(pirical stdy of co"nition and to the philosophy of (ind. t co(!ines an etended ea(ination of a7(ainstrea(7 approach to the i(portance of co(ptationthe 7Co(ptational *heory of 2ind7/C*20 cha(pioned !y Aerry 'odor and Fenon Pylyshyn+ith a preli(inary articlation of analternative approach to ea(inin" the i(portance of co(ptational psycholo"y. *he thesis, in a

sentence, is that C*2 does notprovide a soltion to the philosophical pro!le(s that it is heralded assolvin"indeed, it involves so(e deep confsions a!ot co(pters, sy(!ols, and (eanin"!t thatthis does not nderct the possi!ility that the co(pter paradi"( (ay provide an i(portant resorce/for all +e kno+, perhaps the key resorce0 for the develop(ent of a (atre science of co"nition. nshort, +e +ill !e disappointed if +e look to C*2 for soltions to lon"3standin" philosophical pro!le(sa!ot the (ind. Bt co(ptational psycholo"y is nonetheless a ro!st research pro"ra((e that isdeservin" of philosophical stdy, and the final section of this !ook s""ests an alternative approach tovie+in" co(ptational psycholo"y fro( the standpoint of the philosophy of science rather than that of(etaphysics.


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C*2 clai(s that the (ind literally is a co(pter. nd +hat it is to !e a co(pter, accordin" to C*2, isto !e a device that stores sy(!ols and perfor(s transfor(ations pon those sy(!ols in accordance +ithfor(al /or, (ore precisely, syntactic0 rles. *here are t+o distinct and i(portant strands to this theory.*he first strand is representational and consists in the clai( that individal (ental states, sch asparticlar !eliefs and desires, are relationships !et+een an or"anis( and (ental representations. *hese(ental representations are physically instantiated sy(!ol tokens havin" !oth se(antic and syntactic

properties. *his vie+, taken alone, 'odor so(eti(es calls the 7Gepresentational *heory of 2ind.7 *heGepresentational *heory of 2ind /G*20 is a theory a!ot the natre of individal (ental states. *hesecond thread of C*2 is the clai( that (entalprocesses,sch as for(in" and testin" a hypothesis orreasonin" to a conclsion, are computationalprocesses that the (ind perfor(s pon theserepresentations. *hat is, +hen the (ind (oves fro( one tho"ht to another, it is "eneratin" ne+ (entalrepresentations, and it does so !y applyin" syntactically !ased rles to the representations alreadypresent in it, 8st as a di"ital co(pter "enerates ne+ sy(!olic representations !y applyin"syntactically !ased rles to eistin" representations.

C*2 has "enerated a "reat deal of interest a(on" philosophers !ecase it "oes !eyond clai(s of/(ereN0 e(pirical tility for the co(pter

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paradi"( and (akes s!stantive philosophical clai(s as +ell. *+o sch clai(s are of particlari(portance. 'irst, it is clai(ed that C*2or, (ore specifically, the representational co(ponent ofC*2, G*2provides an accont of ho+ (ental states have sch properties as (eanin", reference,and intentionality. ccordin" to 'odor, (ental states 7inherit7 their se(antic properties fro( those ofthe representations they involve. *he second clai( is at least as !old: na(ely, that C*2 provides a7vindication7 of 7intentional psycholo"y7 /that is, of psycholo"y that is co((itted to a realisticconstral of eplanations in the intentional idio(0 !y sho+in" that intentional eplanations can !e tiedto no(olo"ically !ased casal eplanations that are in no +ay inco(pati!le +ith (aterialis( or +iththe "enerality of physics.

*hese t+o clai(s are !old and a(!itios, to say the least. theory that cold acco(plish either ofthese "oals in isolation +old !e of considera!le i(portance. theory that acco(plished !oth, +hilealso !ein" closely linked to a !r"eonin" (ethodolo"ical approach to actal research in co"nition,cold hardly dra+ (ore attention than it deserved. ndeed, if C*2 scceeds as its advocates clai(, thee(er"ence of the notion of co(ptation +ill have provided the !asis for a revoltion in the stdy of(ind as fnda(ental and i(portant as the Copernican revoltion in astrono(y.

shall ar"e, ho+ever, that +hile the co(pter (ay lti(ately provide the !asis for the etension intopsycholo"y of the 4alilean pro8ect of the (athe(atiDation of science, C*2?s atte(pts to eplainintentionality and to vindicate intentional psycholo"y are !ased pon s!tle !t fnda(entalconfsions. t the heart of C*2 is the clai( that (ental states are relations to (ental representations

to (eanin"fl sy(!olsand that this acconts for their se(antic properties and their intentionality.*he crcial =estions one (st ask of C*2, therefore, are these: /10 Ast +hat does it (ean to say that(ental states are 7relations to (eanin"fl sy(!ols7K nd /@0 8st ho+ is the postlation of (eanin"flsy(!ols spposed to eplain the se(antic properties and the intentionality of (ental statesK *he first=estion calls for an ea(ination of 8st +hat +e are sayin" of a thin" +hen +e call it a 7(eanin"flsy(!ol.7 *he second calls for an application of the reslts of sch an ea(ination to the for(lationsof C*2 offered !y 'odor and Pylyshyn.

t is !oth crios and nfortnate that these =estions have received so little attention fro(


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philosophers of (ind: curious!ecase the =es3

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tions see( so crcial to the assess(ent of a theory that is "enerally ackno+led"ed to !e of "reat interestand i(portance unfortunate!ecase an ea(ination of these =estions ncovers si"nificant

a(!i"ities in sch notions as 7representation,7 7sy(!ol,7 7(eanin",7 and 7intentionality.7 Until +ehave ackno+led"ed these a(!i"ities, it is i(possi!le either to assess C*2 or even to deter(ineeactly +hat it is that it is clai(in".

*his pro!le( has, think, !een toched pon !y so(e +ritersnota!ly !y enneth Sayre and AohnSearle, !oth of +ho( r"e pon s the conclsion that there is so(ethin" a!ot sy(!ols, andparticlarly a!ot sy(!ols in co(pters, that renders the( nsita!le for an eplanation of the(eanin"flness of (ental states. 2y criticis(s of C*2 rn in the sa(e vein. Where part +ays +ithSearle and Sayre is that they look for the pro!le( specifically in the se of sy(!ols in co(pters. n(y vie+, ho+ever, the fnda(ental isse trns ot in the end to have criosly little to do +ithco(pters. *he isse, rather, is +hether the notion of sy(!olic representation provides the !edrockpon +hich a theory of the intentionality of (ental states (ay !e !ilt. 2y ans+er to that is no#andinsofar as the pro8ect of vindicatin" intentional psycholo"y /at least as envisioned !y advocates ofC*20 can !e sho+n to depend pon its a!ility provide a theory of intentionality, that vindication failsas +ell.

Why can?t one esta!lish a theory of intentionality for (ental states pon a fondation of sy(!olicrepresentations in the (indK a( afraid that do not kno+ ho+ to "ive an ans+er to that =estion thatsatisfies (y o+n standards of ri"or in less space than the several chapters it occpies in this !ook, !t shall try to "ive a short ans+er here that (ay prove helpfl and not too inaccrate. When one takes aclose look at +hat one is sayin" +hen one calls so(ethin" a 7(eanin"fl sy(!ol7 or a 7sy(!olicrepresentation,7 it trns ot that one is tacitly sayin" thin"s a!ot the conventions and intentions ofsy(!ol sers. *his is 8st part of +hat +e are sayin" of a thin" in callin" it a sy(!ol, and of +hat +e

are sayin" of a sy(!ol +hen +e say that it has se(antic properties. Bt conventions and intentions ofsy(!ol sers are lti(ately facts a!ot people?s (ental states. nd so any eplanation of theintentionality of (ental states that rests pon the (eanin"flness of sy(!olic representations ends peplainin" the intentionality of (ental states in a +ay that refers to other (eanin"fl (ental states.*hs one i(portant pro!le( +ith C*2?s accont of intentionality is that it trns ot to !e circlar andre"ressive: circlar !ecase it eplains the (eanin"flness of

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(ental states !y appealin" to the (eanin"s of sy(!ols, +hile one (st also eplain the (eanin"flnessof sy(!ols !y appealin" to the (eanin"s of (ental states re"ressive !ecase the eplanation of any

particlar (ental state +ill lti(ately refer !ack to other (ental states.2oreover, it is not only thesemanticproperties of sy(!ols that are conventional in natresyntacticproperties, and the verysymbol types themsel"esare lti(ately dependent pon conventions. /*he factthat so(ethin" is a letterpor an inscription of the )n"lish +ord ?do"? depends pon conventions thatesta!lish the eistence of those sy(!ol types.0 n particlar, the kinds of syntactically !ased rles thatare necessary for compositionalityare conventional in natre: in order to "enerate se(antic propertiesfor co(ple representations, it is not eno"h to have interpretations for the pri(itives and 7synta7 inthe +eak sense of rules for legal concatenationor equi"alence classes of legal transformations.


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Gather, one needs a stron"er kind of synta that involves rles for ho+ syntactic patterns contri!te to(eanin"s of co(ple representationsfor ea(ple, a rle to the effect that if $A$(eans 7O7 and $%$(eans 7,7 then $A!&!%$+ill (ean 7O and .7 *he only +ay +e kno+ of "ettin" this kind ofco(positionality is !y +ay of conventions. t is not clear that there is any other +ay of "ettin"co(positionality at very least, C*2?s advocates +old have to sho+ ho+ se(antic co(position cold!e achieved +ithot the aid of conventions.

o+ of corse this ar"(ent rests pon a particlar constral of +hat it is to !e a sy(!olicrepresentation or to !e a (eanin"fl sy(!ol. Bt, as far as a( a+are, this is the only sense of?sy(!olic representation? and ?(eanin"fl sy(!ol? that +e have. Ene is, of corse, inclined to +onder+hether perhaps +riters like 'odor really (ean so(ethin" different +hen they speak of the (indcontainin" 7(eanin"fl sy(!ols.7 Bt if they do, it is crios that they never infor( the reader thatthey are sin" fa(iliar epressions in novel +ays. ndeed, in one place 'odor "ives a !rief "lance atthis possi!ility only to dis(iss the isse as nlikely to prove i(portant.

t re(ains an open =estion +hether internal representation, so constred, is sfficientlylike natral lan"a"e representation so that !oth can !e called representation ?in the sa(esense?. Bt find it hard to care (ch ho+ this =estion shold !e ans+ered. *here is ananalo"y !et+een the t+o kinds of representation. Since p!lic lan"a"es are conventionaland the lan"a"e of tho"ht is not, there is nlikely to !e morethan an analo"y. f yo arei(pressed !y the analo"y, yo +ill +ant to say that the inner code is a lan"a"e. f yo areni(pressed !y the analo"y, yo +ill +ant to say that the inner code is in so(e sense arepresentational syste( that is not a lan"a"e. Bt in

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neither case +ill +hat yo say affect +hat take to !e the =estion that is seriosly at isse:+hether the (ethodolo"ical ass(ptions of co(ptational psycholo"y are coherent. /'odor19-%: -&3-90

2y contention, !y contrast, is that it does indeed (atter a "reat deal +hether +ords like ?representation?are sed in their sal sense +ithin C*2, !ecase !elieve that the conventionality of lin"isticsy(!ols is not so(ethin" that can !e divorced fro( their sy(!olhood. t is not that +e find anonconventional property called 7(eanin"7 in lin"istic sy(!ols that additionally happens to !econventional in natre. Gather, the very notion of 7(eanin"7 that +e apply to sy(!ols is inter+oven+ith conventionality thro"h and thro"h. nd ths if +e apply these fa(iliar notions of7representation,7 7(eanin",7 and 7synta7 to C*2, +e are led to circlarity and re"ress. s 'odor says,this criticis( does not nderct the (ethodolo"ical ass(ptions of co(ptationalpsychology. Bt thisis only so !ecase co(ptational psycholo"y /that is, e(pirical science inspired !y the co(pterparadi"(0 is not co((itted to the vie+ that its 7(ental representations7 literally are sy(!ols in alan"a"e, as shall ar"e in later chapters. (erely analo"os sa"e of the +ord ?representation? is 8st

fine for co(ptational psycholo"y. *he plasi!ility of C*2?sphilosophicalclai(s, !y contrast, +oldsee( to trnpreciselypon the ass(ption that the 7sy(!ols7 in =estion are 7sy(!ols7 in preciselythe sa(e sense that +e speak of 7sy(!ols7 in a lan"a"e. 'or(aliDation and co(ptation sho+ s ho+to tie (eanin" to casation for /convention3!ased0 linguistic symbols,and not for anythin" else. f(ental representations are so(ethin" other than lin"istic sy(!ols, +e need to see ho+ the link fro((eanin" to casation +orks for so(e ne+ class of entities. *he ar"(ents 'odor and others "ive fortheir clai(s a!ot intentionality and the vindication of intentional psycholo"y si(ply do not "o thro"has stated if +ords like ?representation? and ?sy(!ol? are sed in a (erely analo"os or (etaphorical(anner.


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En the other hand, it is clear that one (i"ht try to develop C*2 in a +ay that divorces the technicalnotion of (ental representation fro( convention3!ased lin"istic si"ns. *he fact that C*2?s advocatesdo not try to do this in any eplicit detail does not (ean that this avene (i"ht not prove (ore fritflin the end. Ene (i"ht, for ea(ple, say that the 7se(antic properties7 of (ental representations are notthe sa(e sort of 7se(antic properties7 possessed !y "arden3variety sy(!ols. *hat is, one (i"ht say thatepressions sch as ?se(antic property? are ho(ony(os, and have different senses +hen applied to

"arden3variety sy(!ols

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and to (ental representations, in +hich case reslts of conceptal analysis of se(antic ter(inolo"y asapplied to discrsive sy(!ols cannot !e sed to create pro!le(s for a theory of (ental representations.

Unfortnately, to the !est of (y kno+led"e, no advocates of C*2 eplicitly prse this corse. Btsince it does see( to !e the only +ay of savin" the theory fro( the reslts of (y conceptal analysis, develop t+o +ays of prsin" this line of tho"ht. *he first is to take casal theories of content likethat spplied in 'odor /19&-0 as spplyin" a casal definitionof se(antic ter(inolo"y as applied to(ental representations. *he second is to treat se(antic ter(inolo"y as applied to (entalrepresentations as !ein" theoretical and open3ended in character: that is, to treat ter(s sch as?(eanin"fl? and ?referential? as applied to (ental representations as ter(s +hose (eanin" +e do notpresently kno+ !t (i"ht discover as the reslt of frther investi"ation. shall ar"e in Part thatneither of these strate"ies see(s likely to !e a!le to provide an accont of intentionality or to vindicateintentional psycholo"y.

*hese pro!le(s for C*2 as a philosophical thesis, ho+ever, do not entail that the co(pter paradi"(is of no se for the philosopher or the e(pirical researcher. 'or think that there is a (ch !etter +ayto nderstand the natre and i(portance of the co(pter paradi"( for the stdy of co"nition. f oneadopts this alternative vie+, the i(portance of providin" an accont of intentionality +anessi"nificantly, +hile the need to 8stify intentional psycholo"y disappears alto"ether. *o arrive at this

standpoint, ho+ever, +e (st cease lookin" to C*2 as a sorce of soltions to old philosophicalpDDles and !e"in to look at co(ptational psycholo"y as a research pro"ra((e in psycholo"y fro(the perspective of historians and philosophers of science.

*he !asis of the alternative approach is the pre(ise that t+o of the traditional distin"ishin" (arks of a(atre science have !een the (athe(atiDation of its eplanations and the clarification of connections!et+een the do(ain and the la+s of that science and those of other areas of kno+led"e. So, to take aparadi"( ea(ple, che(istry pro"ressed to+ards (athe(atical (atrity thro"h the develop(ent ofthe periodic ta!le, the notion of "alences,and the discovery of rles "overnin" reactions !et+eendifferent classes of (olecles. t pro"ressed to+ards connective (atrity as the eplanations "iven inche(ical ter(s +ere a!le to provide eplanations for pheno(ena descri!ed at a hi"her level /e."., asdescri!ed in the voca!laries of (etallr"y or "enetics0 and as cate"ories sch as "alence+ere in trn

eplained at a lo+er level in ter(s of sch ideas as ele(entary particles and or!itals.

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*he interpretation of the i(portance of the co(pter paradi"( that +ish to r"e is the follo+in":+hat the notion of co(ptation may!e a!le to provide for the e(pirical scientist is the ri"ht kind oftechnical (achinery for the (athe(atiDation of the stdy of co"nitionparticlarly, co"nitivepsycholo"y. / e(phasiDe the +ord ?(ay? !ecase seek only to ill(inate +hat co(ptational


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psycholo"y 'ould pro"ide if successful,and not to (ake any predictions a!ot its evental sccesses orfailres.0 *hat is, +hat co(pter science "ives s is an a!stract voca!lary that (i"ht trn ot toprovide the resorces for psycholo"y to pro"ress to+ards (athe(atical (atrity. think that it shold!e clear that this is of enor(os interest, even +ithot the philosophical !enefits clai(ed for C*2.Srely a lar"e part of +hat psycholo"y is a!ot is providin" an inventory of co"nitive processes,7(appin"7 the relations !et+een these, 7nlockin" the !lack !oes7 nderlyin" hi"h3level processes !y

specifyin" lo+er3level processes that +old accont for the(, and sho+in" ho+ (ental processes areconnected to !ehavior. *hat is,partof +hat psycholo"y is a!ot is specifyin" theformof the (ind !ytracin" ot the fnctional relations (ental states !ear to one another and to !ehavior. 2any researchersinterested in co"nition have staked their careers pon their !elief that co(ptational notions allo+ the(to carry ot this pro8ect in +ays that +ere previosly navaila!le. ndeed, the stren"th of this !elief isevidenced !y the e(er"ence of 7co"nitive science7 as an approach to the (ind that is or"aniDed arondthe pre(ise that co"nitive processes can !e descri!ed in co(ptational ter(s. think this researchpro8ect is of "reat interest re"ardless of +hether the notion of co(ptation can contri!te to thesoltion of any philosophical pro!le(s as +ell.

2oreover, vie+ed in this +ay, co"nitive science as an e(pirical research pro"ra((e is not i(periled!y (y criticis(s of C*2. What ar"e a"ainst C*2 is that if yo take it as central to the very notion

of computationthat co(ptation consists in the (aniplation of meaningful symbols,then there areserios pro!le(s involved in sayin" that co"nition is co(ptation. f, on the other hand, +hat isessential to the notion of co(ptation isfunctional specifiabilityin, say, the for( of a (achine ta!lethese pro!le(s do not arise. f co"nitive science is oriented to+ards the thesis that cogniti"eprocesses are functionally specifiable,then it can atte(pt to apply the technical resorces of co(pterscience to the do(ain of psycholo"y +ithot +orryin" a!ot pro!le(s +ith the notions ofsymbol orrepresentation. ndeed, one (i"ht even propose theories that depend pon the pre(ise that there are(en3

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tal states or !rain states that play a role in tho"ht, a role that isformally analogous tothe roles played!y sy(!ols in the eection of particlar co(pter pro"ra(s, +ithot threat of incoherence fro((isse of sch +ords as ?sy(!ol? and ?(eanin"fl?. /Ene (i"ht, +ith so(e risk, even se the +ord?sy(!ol? in descri!in" sch states, so lon" as one +as carefl that the ille"iti(ate i(portation of theordinary (eanin" of the +ord ?sy(!ol? did not do any illicit +ork in one?s eplanations.0

Ef corse, +hat one loses in this alternative is the hope C*2 ecited of findin" a level of eplanationa do(ain of (eanin"fl (ental representations over +hich (ental co(ptations are definedat+hich there is a clear (eetin" of the +ays !et+een (entalistic description cast in the intentional idio(and one of the natral sciences. En this vie+, co"nitive science does not 7close the "ap7 !et+een (indand natre. Here, ho+ever, there is a partin" of the +ays !et+een the interests of the philosopher of

(ind and those of the e(pirical scientist. 'or the co(pter paradi"( (i"ht help psycholo"y pro"ressto one or !oth types of scientific (atrity +ithot providin" a philosophical accont of intentionality inthe process. 'irst, it (i"ht provide the tools for the (athe(atiDation of psycholo"y +ithot providin"for connective (atrity as +ell. Bt it does see( likely that a "ood (athe(atiDation of co"nitiveeplanation is 8st the sort of thin" that +old !e helpfl in correlatin" states specified in theintentional idio( +ith states specified in nerolo"ical ter(s: that is, it is ar"a!le that the only +ay offindin" ot ho+ co"nitive states are instantiated is to find ot +hat in the !rain has the ri"ht/fnctional0 7shape7 to realiDe the(. So if connection !et+een co"nitive eplanation and other kinds ofeplanation is to take place, it (ay partially !e throughthe (athe(atiDation of !oth levels of


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eplanation. nd for this it is a plasi!le hypothesis that co(pter science provides the appropriateresorces.

Bt it is i(portant to see that one (i"ht "et the kind of connectivity that the scientist desires +ithotthere!y solvin" any philosophical pro!le(s. *he researcher co((itted to intentional eplanation andnatral eplanation +ants to find ot +hat neral processes are specially associated 'ith+hatintentionally specified processes. nd she is interested in this association 8st to the etent that

intentional and natralistic predictions +ill tracone another. *he (etaphysical natre of this 7specialassociation7 really does not (atter as far as e(pirical science is concerned. )(pirical science is lar"ely!lind to the differences !et+een relationships stron"er than e(pirical ade=acy, and hence a "oodinte"rated psycholo"ical theory cold !e e=ally co(pati!le +ith (aterial3

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is( and spervenience or +ith thoro"h"oin" parallelist dalis(. nd this, think, shold !e vie+ed asa virte rather than a vice: in (y !ook, consistency +ith a +ide ran"e of ontolo"ical options conts as asi"nificant virte for an e(pirical research pro"ra((e.

o+ there is a sense in +hich sch an inte"rated psycholo"y +old provide an 7accont7 ofintentionality and a sense in +hich it +old not. f !y 7an accont of intentionality7 one (eans (a)a(odel of the relations !et+een intentional states, sti(li, and !ehavior, and (b)a specification of thenatral syste(s thro"h +hich intentional states and processes areto se an intentionally netral ter(reali*ed,then an inte"rated psycholo"y (i"ht +ell involve an 7accont of intentionality.7 Bt if 7anaccont of intentionality7 (eans so(ethin"strongersay, if it involves providin" natral conditionspon +hich intentional properties +old ha"eto spervene, then an inte"rated psycholo"y (i"ht +ellnot provide thiskind of 7accont of intentionality.7 !elieve, ho+ever, that it is fnda(entally(is"ided to seek sch a natralistic accont of intentionality, for reasons that shall develop inchapters 9 and 11. f a( ri"ht, then ina!ility to provide an accont of intentionality in this stron"sense is not a falt.

shall ar"e for a si(ilar attitde to+ards the other "oal C*2 has so"ht to achieve: that ofvindicatin" intentional psycholo"y. *o pt it very !riefly, do not !elieve that intentional psycholo"y ispresently in need of vindication. *he perceived need for a vindication trned pon so(e concerns a!ot(ethodolo"y and ontolo"y that ca(e to pro(inence in the +ritin"s of !ehaviorists and redctionists.Ene (i"ht do +ell to ask +hether these concerns o"ht to have srvived the theories that !ro"ht the(to pro(inence. Bt even if one finds these concerns to !e serios ones, they (st at very least !e ptoff for the present. By 8st a!ot everyone?s reckonin", any fll3scale (eetin" of the +ays that (i"httake place !et+een intentional eplanation and neroscience /(ch less physics0 is a lon" +ays a+ayand depends pon a "reat deal of research, (ch of +hich al(ost has to !e prsed thro"h top3do+nstrate"ies in co"nitive psycholo"y. So, in a sense, any real assess(ent of co"nitivis(?s co(pati!ility+ith the "enerality of physical eplanation cold only take place once +e had a reasona!ly sccessfl

predictive co"nitive psycholo"y.Ef corse +e all look for occasions +hen or top3do+n strate"ies "et s to a level +here +e can findso(e plasi!le candidate for a kno+n nerolo"ical (echanis( that has the ri"ht fnctional featres tospport the kind of co"nitive process +e have postlated. Sch (o(ents are land3

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(arks that provide so(e of the !est kinds of reasons to !elieve one?s research is on the ri"ht track. *hat


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!ein" said, it is nonetheless the case that /10 intentional eplanation see(s an indispensa!le startin"point for co"nitive psycholo"y, re"ardless of +hether sch research +old lti(ately allo+ s to7thro+ a+ay the ladder7 /@0 it cold, in principle, trn ot that research in co"nitive science coldprodce a "ood predictive psycholo"y +ithot ever hookin" p +ith neroscience in a co(prehensivefashion /e."., +e +old not thro+ ot psychophysics if +e cold not prodce netral (odels to accontfor the data0 /#0 if this +ere to happen, it is not at all clear that +e shold, as a reslt, re"ard sch

psycholo"ical theories as fla+ed, (ch less (etaphysically perverse and /J0 in the (eanti(e, it isa!soltely pointless to epect e(pirical researchers to care a!ot +hether their +ork (eets schideolo"ical tests as confor(ity +ith one?s favorite ontolo"ical theory.

n short, do not think that intentional psycholo"y is in need of vindication at the present ti(e. *hepressin" =estion for the philosophy of psycholo"y is +hether intentional eplanation can !esyste(atiDed and (apped ot sin" so(ethin" like the techni=es afforded s !y the notion ofco(ptation or !y so(e alternative notions, and +hether in the corse of this pro8ect or ordinary(entalistic notions like 7desire,7 7!elief,7 and 78d"(ent7 +ill !e retained, !ilt into a lar"erfra(e+ork, transfor(ed, or a!andoned alto"ether. Certain otco(es of this pro8ect (i"ht call for thereassess(ent of intentional psycholo"y. /nd of corse there are already those +ho !elieve that it is a(istake to vie+ it as an eplanatory science in the first place.0 *here is a separate, and lar"ely

e(pirical =estion a!ot ho+ co"nitive states are realiDed thro"h specific physiolo"ical strctres.*he connections !et+een the sccess or failre of this pro8ect and the stats of intentional psycholo"yare far (ore tenos, !t really need not !e fretted over at this sta"e of the "a(e.

*o repeat, on (y readin" of the si"nificance of the co(pter paradi"(, +hat it offers is a pro8ect that(i"ht hasten the pro"ress of psycholo"y to+ards scientific (atrity !y providin" the ri"ht technicalresorces for (athe(atiDin" the fnctional relationships that (ental states !ear to one another and to!ehaviors. nterpreted in this fashion, the co(ptational approach to co"nition is one that isdistin"ished principally !y the conceptal tools it !orro+s fro( co(pter science. Ho+ever, theco(ptational approach is only one research pro"ra((e a(on" several that seek to provide the ri"htfor(al tools for stdyin" co"nition. t is a research pro"ra((e that has rivals that spply different toolsfor the (athe(atiDation of psycholo"y. ota!le a(on" these are the infor(ation3

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theoretic approach favored !y Sayre and the net+ork3!ased (athe(atical (odels of varios sortsoffered over the past thirty years !y Pitts and 2cClloch, 4ross!er", nderson, and others. Whatfor(al techni=es end p providin" the !est descriptions is a =estion to !e ans+ered !y the fertility ofthese research pro8ects.

What this !ook calls for, then, is a separation of t+o kinds of isses. *he first set of isses involves=estions a!ot ho+ to co(pare co(petin" theories a!ot the (ind that e(er"e ot of e(piricalscience. 'or ea(ple, apart fro( their a!ilities to "ive so(e description of the pheno(ena in their o+n

canonical voca!laries, 8st +here do t+o approaches to co"nition, sch as C*2 and connectionis(,really differK What are the 7"ood3(akin"7 =alities that are relevant to the assess(ent of e(piricaltheories in psycholo"y, and +hich are possessed in "reater a!ndance !y +hose theoriesK *he secondset of isses is (ade p of (ore prely philosophical =estions a!ot the (ind3!ody pro!le(, the eact(etaphysical relationship !et+een (ental states and the physical states thro"h +hich they arerealiDed, and atte(pts to "ive a lo"ically necessary and sfficient accont of notions sch as (eanin"and intentionality. t is the thesis of this !ook that, contrary to poplar r(or, C*2 does nothin" tosolve the latter pro!le(s. onetheless, it is =ite possi!le to 7!o+dleriDe7 C*2 in a fashion that avoidsthe pro!le(s of interpretive re"ress and to constre it as a special version of (achine fnctionalis(


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and interpreted in this fashion, co(ptational psycholo"y can !e seen as an interestin" contender +ithrespect to the first set of isses. With C*2?s clai(s to solvin" philosophical pro!le(s ot of the +ay,ho+ever, there is no+ a level playin" field, and co(ptational psycholo"y (ay !e co(pared +ith itsco(petitors in ter(s of their prely scientific (erits. nd in a ronda!ot +ay, think this conts aspro"ress.

" -rie+ uide to T)is -oo/*his !ook is divided into for sections. Part , co(prisin" chapters 1 thro"h #, "ives an eposition ofC*2 and of its clai(s to solve i(portant philosophical pro!le(s. t also provides an initial state(entof so(e potential pro!le(s for C*2 arisin" fro( criticis(s raised !y Searle and Sayre. (ake a casethat their criticis(s are not definitive, and call for a (ore carefl analysis of the notions of 7sy(!ol,77synta,7 and 7sy(!olic (eanin".7 *his analysis is provided in Part . Chapter J presents aconventionalist analysis of sy(!ols, synta, and sy(!olic (ean3

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in", +hich is then applied to sy(!ols in co(pters in chapter % and defended a"ainst so(e likelyo!8ections in chapter 6. /*he reader +ho co(es ot of chapter J +ith !rnin" o!8ections +ill losenothin" !y readin" chapter 6 !efore chapter %.0

*he reslts of this analysis are then applied in Part /chapters - thro"h 90 in a criti=e of thephilosophical clai(s of C*2. Chapter - ar"es that, if yo interpret C*2?s talk of 7sy(!ols,77synta,7 and 7se(antics7 in the ordinary convention3laden +ay, yo are left +ith an accont that iscirclar and re"ressive. Chapter & ar"es that C*2 fares no !etter if the se(iotic voca!lary isreconstrcted in a nonconventionalist +ay. n short, C*2 (aintains an illsion of eplainin"intentionality only !y slippin" !ack and forth !et+een se(iotic notions !ased on conventional sy(!olsand talk of an alternative 7pre se(antics.7 Chapter 9 !riefly (akes the case that C*2 is nlikely to !espple(ented !y an independent natraliDation of content: so(e featres of the (ind do not see(

sscepti!le to natraliDation at all, +hile others see( likely to !e natraliDed /if at all0 only in a fashioninco(pati!le +ith the constraints laid do+n !y C*2. *he dialectical sitation at the end of Part isthat C*2?s clai(s to prodcin" distinctively philosophical frit have !een nder(ined.

Part then presents an alternative vie+ of the i(portance of the co(pter paradi"(. Chapter 1$otlines ho+ co(ptation (i"ht provide psycholo"y +ith i(portant "ood3(akin" =alities +ithotnatraliDin" intentionality or vindicatin" intentional psycholo"y. *he !ook concldes, in chapter 11,+ith a philosophical ea(ination of the ass(ptions that intentionality needs natraliDin" and (entalstates need vindicatin". ar"e that, in the a!sence of stron" a prioristic ar"(ents for natralis(, +eare !etter off lettin" the special sciences florish as !est they (ay and shapin" or (etatheoretic vie+sa!ot intertheoretic connections on the !asis of the shape that real psycholo"y takes rather than pon

any preconceived notions of +hat itshouldlook like.

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$"RT I0

C1$UT"TIN"#IS1 "N ITS CRITICS

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C)apter ne0

T)e Computational T)eory o+ 1ind

*he past thirty years have +itnessed the rapid e(er"ence and s+ift ascendency of a trly novelparadi"( for nderstandin" the (ind. *he paradi"( is that of (achine co(ptation, and its inflencepon the stdy of (ind has already !een !oth deep and far3reachin". si"nificant n(!er ofphilosophers, psycholo"ists, lin"ists, neroscientists, and other professionals en"a"ed in the stdy ofco"nition no+ proceed pon the ass(ption that co"nitive processes are in so(e sense co(ptationalprocesses and those philosophers, psycholo"ists, and other researchers +ho do notproceed pon this

ass(ption nonetheless ackno+led"e that co(ptational theories are no+ in the (ainstrea( of theirdisciplines.

Bt if there is "eneral a"ree(ent that the paradi"( of (achine co(ptation (ay have si"nificanti(plications for !oth the philosopher of (ind and the e(pirical researcher interested in co"nition, thereis no sch a"ree(ent a!ot +hat these i(plications are. *here is, perhaps, little do!t that co(pter(odelin" can !e a po+erfl tool for the psycholo"ist, (ch as it is for the physicist and the(eteorolo"ist. Bt not all researchers are a"reed that the co"nitive processes they (ay (odel on aco(pter are the(selves co(ptations, any (ore than the stor(s that the (eteorolo"ist (odels areco(ptations.

Si(ilarly, there is si"nificant disa"ree(ent a(on" philosophers a!ot +hether the paradi"( of

(achine co(ptation provides a literal characteriDation of the (ind or (erely an allrin" (etaphor.*hree alternative +ays of assessin" the i(portance of the co(pter paradi"( stand ot. *he (ost(odest possi!ility is that the co(pter (etaphor +ill

5 1& 5

prove an a!le catalyst for "eneratin" theories in psycholo"y, in (ch the sort of +ay that n(erosother (etaphors have so often played a role in the develop(ent of other sciences, yet in sch a fashionthat little or nothin" a!ot co(ptation per se +ill !e of direct relevance to the eplanatory vale of theresltin" theories. second and sli"htly stron"er possi!ility is that the conceptal (achinery e(ployedin co(pter science +ill provide the ri"ht sorts of tools for allo+in" psycholo"y /or at least parts ofpsycholo"y0 to !eco(e a ri"oros science, in (ch the fashion that conceptal tools sch as Cartesian"eo(etry and the calcls provided a !asis for the e(er"ence of e+tonian (echanics, and differential"eo(etry (ade possi!le the relativistic physics +hich spplanted it. En this vie+, +hich +ill !ediscssed in the final chapter of this !ook, +hat the co(pter paradi"( (i"ht contri!te is the !asis forthe (atration of psycholo"y !y +ay of the (athe(atiDation of its eplanations and the connections!et+een intentional eplanation and eplanation cast at the level of so(e lo+er3order /e.".,nerolo"ical0 processes thro"h +hich intentional states and processes are realiDed. *his vie+ isco((itted to the thesis that the (ind is a co(pter only in the very +eak sense that the interrelations!et+een (ental states have for(al properties for +hich the voca!lary associated +ith co(ptation


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provides an apt characteriDationthat is, to the vie+ that there is a description of the interrelations of(ental states and processes that is iso(orphic to a co(pter pro"ra(. *his thesis involves noco((it(ent to the stron"er vie+ that ter(s like ?representation?, ?sy(!ol?, and ?co(ptation? play anystron"er role in eplainin" +hy (ental states and processes are mentalstates and processes, !t onlythe +eaker vie+ that, "iven that +e (ay posit sch states and processes, their 7for(7 (ay !e descri!edin co(ptational ter(s. /o (i"ht say that, on this vie+, the (ind is 7co(ptational7 in the sa(e

sense that a relativistic niverse is 7differential.70 *he third and stron"est vie+ of the relevance of(achine co(ptation to psycholo"yone ea(ple of +hich +ill !e the (ain focs of this !ookisthat notions sch as 7representation7 and 7co(ptation7 not only provide the psycholo"ist +ith thefor(al tools she needs to do her science in a ri"oros fashion, !t also provide the philosopher +ithfnda(ental tools that allo+ for an analysis of the essential nature of cognitionand for the soltion ofi(portant and lon"3standin" philosophical pro!le(s.

*his !ook ea(ines one particlar application of the paradi"( of (achine co(ptation to the stdy of(ind: na(ely, the 7Co(ptational

5 19 5

*heory of 2ind7 /C*20 advocated in recent years !y Aerry 'odor /19-%, 19&$a, 19&1, 19&-, 199$0 andFenon Pylyshyn /19&$, 19&J0. Ever the past t+o decades, C*2 has e(er"ed as the 7(ainstrea(7 vie+of the si"nificance of co(ptation in philosophy. ts advocates have articlated a very stron" position:na(ely, that co"nition literally is co(ptation and the (ind literally is a di"ital co(pter. C*2 isco(prised of t+o theses. *he first is a thesis a!ot the natre of intentional states, sch as individal!eliefs and desires. ccordin" to C*2, intentional states are relational states involvin" an or"anis( /orother co"niDer0 and (ental representations. *hese (ental representations, (oreover, are to !enderstood on the (odel of representations in co(pter stora"e: in particlar, they are sy(!ol tokensthat have !oth syntactic and se(antic properties. *hese sy(!ols inclde !oth se(antic pri(itives andco(ple sy(!ols +hose se(antic properties are a fnction of their syntactic strctre and the se(anticvales of the pri(itives they contain. *he second thesis co(prisin" C*2 is a!ot the natre ofco"nitive processesprocesses sch as reasonin" to a conclsion, or for(in" and testin" a hypothesis,+hich involve chains of !eliefs, desires, and other intentional states. ccordin" to C*2, co"nitiveprocesses are co(ptations over (ental representations. *hat is, they are casal se=ences of tokenin"sof (ental representations in +hich the relevant casal re"larities are deter(ined !y the syntacticproperties of the sy(!ols and are descri!a!le in ter(s of for(al /i.e., syntactic0 rles. *he re(ainder ofthis chapter +ill !e devoted to clarifyin" the natre and stats of these t+o clai(s.

s +e shall see in chapter @, C*2?s advocates have also (ade a very persasive case that vie+in" the(ind as a co(pter allo+s for the soltion of si"nificant philosophical pro!le(s: nota!ly, they havear"ed /10 that it provides an accont of the intentionality of (ental states, and /@0 that it sho+s thatpsycholo"y can e(ploy eplanations in the intentional idio( +ithot involvin" itself in (ethodolo"ical

or ontolo"ical difficlties. *he clai(s (ade on !ehalf of C*2 ths fall into the third and stron"estcate"ory of attitdes to+ards the pro(ise of the co(pter paradi"(. *he task ndertaken in thes!se=ent chapters of this !ook is to evalate these clai(s that have !een (ade on !ehalf of C*2 andto provide the !e"innin"s of an alternative nderstandin" of the i(portance of the co(pter paradi"(for the stdy of co"nition. n particlar, +e shall ea(ine /10 +hether C*2 scceeds in solvin" thesephilosophical pro!le(s, and /@0 +hether the +eaker possi!ility of its providin" the !asis for a ri"orospsycholo"y in any +ay depends pon either the


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5 @$ 5

nderstandin" of co"nition and co(ptation endorsed !y C*2 or its a!ility to eplain intentionalityand vindicate intentional psycholo"y.

&.&0

Intentional StatesC*2 is a theory a!ot the natre of intentional states and co"nitive processes. *o nderstand +hat this(eans, ho+ever, +e (st first !eco(e clear a!ot the (eanin"s of the epressions ?intentional state?and ?co"nitive process?. *he epression ?intentional state? is sed as a "eneric ter( for (ental states of an(!er of kinds reco"niDed in ordinary lan"a"e and co((onsense psycholo"y. So(e paradi"(ea(ples of intentional states +old !e

belie"ing/8d"in", do!tin"0 that sch3and3sch is the case,

desiringthat sch3and3sch shold take place,

hopingthat sch3and3sch +ill take place,

fearingthat sch3and3sch +ill take place.*he characteristic featre of intentional states is that they are about somethingor directed to'ardssomething. *his featre of directednessor intentionalitydistin"ishes intentional states !oth fro(!rte o!8ects and fro( other (ental pheno(ena sch as =alia and feelin"s, none of +hich is a!otanythin". *he epressions ?intentional states? and ?co"nitive states? denote the sa(e class of (entalstates, !t the t+o ter(s reflect different interests. *he ter( ?intentionality? is e(ployed pri(arily inphilosophy, +here it is sed to denote specifically this directedness of certain (ental states, a featre+hich is of i(portance in nderstandin" several i(portant philosophical pro!le(s, incldin" opacityand transparency of reference and kno+led"e of etra(ental o!8ects. *he ter( ?co"nition? is (ostco((only e(ployed in psycholo"y, +here it is sed to denote a do(ain for scientific investi"ation. ssch, its scope and (eanin" are open to so(e de"ree of ad8st(ent and chan"e as the science of

psycholo"y pro"resses. third ter( sed to indicate this sa(e do(ain is ?propositional attitde states?.*his epression sho+s the inflence of the +idely accepted analysis of co"nitive states as involvin" anattitude/sch as !elievin" or do!tin"0 and a contentthat indicates the o!8ect or state of affairs to+hich the attitde is directed. Since the contents of (ental states are often closely related topropositions, sch attitdes are so(eti(es calledpropositionalattitdes. *hese three e3

5 @1 5

pressions +ill !e sed interchan"ea!ly in the re(ainder of this !ook. n places +here there is littledan"er of (isnderstandin", the (ore "eneral epression ?(ental states? +ill also !e sed to referspecifically to intentional states.

&.20

1ental State "s3riptions in Intentional $sy3)olo*y and !ol/ $sy3)olo*y

ttri!tions of intentional states sch as !eliefs and desires play an i(portant role in or ordinarynderstandin" of orselves and other h(an !ein"s. We descri!e (ch of or lin"istic !ehavior inter(s of the epression of or !eliefs, desires, and other intentional states. We eplain or o+n actionson the !asis of the !eliefs and intentions that "ided the(. We eplain the actions of others on the !asis


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of +hat +e take to !e their intentional states. Sch eplanations reflect a "eneral fra(e+ork forpsycholo"ical eplanation +hich is i(plicit in or ordinary nderstandin" of h(an tho"ht andaction. cardinal principle of this fra(e+ork is that people?s actions can often !e eplained !y theirintentional states. shall se the ter( ?intentional psycholo"y? to refer to any psycholo"y that /a0(akes se of eplanations involvin" ascriptions of intentional states, and /b0 is co((itted to a realisticinterpretation of at least so(e sch ascriptions.

*his sa"e of the epression ?intentional psycholo"y? shold !e distin"ished fro( the co((on sa"eof the crrently poplar epression ?folk psycholo"y?. *he epression ?folk psycholo"y? is sed !y (anyconte(porary +riters in co"nitive science to refer to a cltre?s loosely knit !ody of co((onsense!eliefs a!ot ho+ people are likely to think and act in varios sitations. t is called 7psycholo"y7!ecase it involves an i(plicit ontolo"y of (ental states and processes and a set of /lar"ely i(plicit0ass(ptions a!ot re"larities of h(an tho"ht and action +hich can !e sed to eplain !ehavior. t iscalled 7folk7 psycholo"y !ecase it is not the reslt of ri"oros scientific in=iry and does not involveany ri"oros scientific research (ethodolo"y. 'olk psycholo"y, ths nderstood, is a proper s!set of+hat a( callin" intentional psycholo"y. t is asubsetof intentional psycholo"y !ecase it e(ploysintentional state ascriptions in its eplanations. t is only apropers!set !ecase one cold havepsycholo"ical eplanations cast in the intentional idio( that +ere the reslt of ri"oros in=iry and

+ere not co((itted to the specific set of ass(ptions characteristic of any "iven cltre?sco((onsense vie+s a!ot the (ind. 2any of 'red?s theories, for ea(ple,

5 @@ 5

fall +ithin the !onds of intentional psycholo"y, since they involve appeals to !eliefs and desires yetthey fall otside the !onds of folk psycholo"y !ecase 'red?s theories are at least atte(pts atri"oros scientific eplanation and not (ere distillations of co((onsense +isdo(. Si(ilarly, (anyconte(porary theories in co"nitive psycholo"y e(ploy eplanations in the intentional idio( that fallotside the !onds of folk psycholo"y, in this case !ecase the states picked ot !y their ascriptionsoccr at an infraconscios level +here (ental states are not attri!ted !y co((onsense nderstandin"sof the (ind.

n nderstandin" the i(portance of C*2 in conte(porary psycholo"y and philosophy of (ind, it+old !e hard to overe(phasiDe this distinction !et+een the (ore inclsive notion of intentionalpsycholo"y, +hich e(!races any psycholo"y that is co((itted to a realistic constral of intentionalstate ascriptions, and the narro+er notion of folk psycholo"y, +hich is !y definition confined toprescientific co((onsense nderstandin"s of the (ental. 'or C*2?s advocates +ish to defend theinte"rity of intentional psycholo"y, +hile ad(ittin" that there (ay !e si"nificant pro!le(s +ith thespecific set of precritical ass(ptions that co(prise a cltre?s folk psycholo"y. En the one hand,'odor and Pylyshyn ar"e that the intentionally laden eplanations present in folk psycholo"y are =itesccessfl,L1M that folk psycholo"y is easily 7the (ost sccessfl predictive sche(e availa!le for

h(an !ehavior7 /Pylyshyn 19&J: @0, and even that intentional eplanation is indispensa!le inpsycholo"y.L@M En the other hand, advocates of C*2 are often (ore critical of thespecific"eneraliDations i(plicit in co((onsense nderstandin"s of (ind. 'olk psycholo"y (ay provide a "oodstartin" point for doin" psycholo"y, (ch as ani(al ter(s in ordinary lan"a"e (ay provide a startin"point for Doolo"ical taono(y or !illiard !all analo"ies (ay provide a startin" point for (echanics !t(ore ri"oros research is likely to prove co((onsensical ass(ptions +ron" in psycholo"y, (ch asit has in !iolo"y and physics.L#M 'olk psycholo"y is ths vie+ed !y these +riters as a protoscience otof +hich a scientific intentional psycholo"y (i"ht e(er"e. Ene thin" that +old !e needed for thistransition to a scientific intentional psycholo"y to take place is ri"oros e(pirical research of the sort


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ndertaken in the relatively ne+ area called co"nitive psycholo"y.LJM Sch e(pirical research +old !eresponsi!le, a(on" other thin"s, for correctin" sch ass(ptions of co((on sense as (ay prove to !e(istaken. What is vie+ed as the (ost si"nificant shortco(in" of co((onsense psycholo"y, ho+ever,is not that it contains erroneos "eneraliDations, !t that its "eneraliDations are not nited !y a sin"letheo3

5 @# 5

retical fra(e+ork.L%M C*2 is an atte(pt to provide sch a fra(e+ork !y spplyin" /a0 an accont ofthe natre of intentional states, and /b0 an accont of the natre of co"nitive processes.

&.40

CT15s Representational "33ount o+ Intentional States

*he first thesis co(prisin" C*2 is a representational account of the nature of intentional states. 'odorprovides a clear otline of the !asic tenets of this accont in the follo+in" five clai(s, offered in theintrodction to+eresentations,p!lished in 19&1:

/a0 Propositional attitde states are relational.

/b0 (on" the relata are (ental representations /often called 7deas7 in the olderliteratre0.

/c0 2ental representationLsM are sy(!ols: they have !oth for(al and se(antic properties.

/d0 2ental representations have their casal roles in virte of their for(al properties.

/e0 Propositional attitdes inherit their se(antic properties fro( those of the (entalrepresentations that fnction as their o!8ects. /'odor 19&1: @60

Clai(s /a0 thro"h /c0 provide 'odor?s vie+s pon the natre of intentional states, +hile clai(s /d0

and /e0 provide the (eans for connectin" this representational accont of intentional states +ith aco(ptational accont of co"nitive processes and an accont of the intentionality of the (ental,respectively.

'odor spplies a (ore for(al accont of the natre of intentional states in sychosemantics,p!lishedin 19&-. *here he characteriDes the natre of intentional states /propositional attitdes0 as follo+s:

Claim -/the natre of propositional attitdes0:

'or any or"anis( , and any attitdeAto+ard the proposition, there is a/?co(ptational?3?fnctional?0 relation+and a (ental representationMsch that

M(eans that, and

hasAiff !ears+toM. /'odor 19&-: 1-0En 'odor?s accont, Aones?s !elievin" that t+o is a pri(e n(!er consists in Aones !ein" in a particlarkind of fnctional relationship+to a (ental representationM. *his (ental representationMis asy(!ol token, pres(a!ly instantiated in so(e fashion in Aones?s nervos syste(. Mhas se(anticproperties: in particlar,M(eans that t+o is a

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pri(e n(!er. nd Aones !elieves that t+o is a pri(e n(!er +hen and only +hen he is relation+toM.

*here are so(e "larin" nclarities a!ot references to types and tokens of attitdes and representationsin this for(lation, !t so(e of these are clarified +hen 'odor provides a 7crder !t (ore intelli"i!le7"loss pon his accont of the natre of intentional states:

*o !elieve that sch and sch is to have a (ental sy(!ol that (eans that sch and schtokened in yor head in a certain +ay it?s to have sch a token ?in yor !elief !o,? as ?llso(eti(es say. Correspondin"ly, to hope that sch and sch is to have a token of that sa(e(ental sy(!ol tokened in yor head, !t in a rather different +ay it?s to have it tokened ?inyor hope !o.? . . . nd so on for every attitde that yo can !ear to+ard a proposition andso on for every proposition to+ard +hich yo can !ear an attitde. /'odor 19&-: 1-0

En the !asis of this "loss, it see(s (ost reasona!le to read 'odor?s for(lation as follo+s:

The /ature of ropositional Attitudes (Modified)

'or any or"anis( , and any attitde3token aof typeAto+ard the proposition, there is a/?co(ptational?3?fnctional?0 relation+and a (ental representation token tof typeMsch that

t(eans that!y virte of !ein" anM3token, andhas an attitde of typeAiff !ears+to a token of typeM.L6M

While there are ar"a!ly so(e si"nificant residal nclarities a!ot 'odor?s for(lation in spite ofthese clarifications,L-M 'odor does (ake the (ain point ade=ately clear: na(ely, that it is therelationship !et+een the or"anis( and its (ental representations that is to accont for the fact thatintentional states have the se(antic properties and intentionality that they have. n the passa"e already=oted fro(+eresentations,for ea(ple, he +rites that intentional states 7inherit their se(anticproperties fro( those of the (ental representations that fnction as their o!8ects7 /'odor 19&1: @60.nd in that essay he also +rites that 7the o!8ects of propositional attitdes are sy(!ols /specifically,(ental representations07 and that 0this fact accounts for their intensionality and semanticity0/i!id., @%,

e(phasis added0.L&M*he first thesis co(prisin" C*2 is ths a representational account of the nature of intentional states.En this accont, intentional states are relations to (ental representations. *hese representations aresy(!ol tokens havin" !oth syntactic and se(antic properties, and intentional

5 @% 5

'i"re 1

states 7inherit7 their se(antic properties and their intentionality fro( the representations they involve/see fi". 10.

&.60

Semanti3 Compositionality

n i(portant featre of this accont lies in the fact that the sy(!ols involved in (ental representationhave !oth se(antic and syntactic properties, and (ay !e vie+ed as tokens in a 7lan"a"e of tho"ht,7


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so(eti(es called 7(entalese.7 ie+in" the syste( of (ental representations as a lan"a"e +ith !othse(antic and syntactic properties allo+s for the possi!ility of compositionality of meaning. *hat is, thesy(!ols of (entalese are not all leical pri(itives. nstead, there is a finite stock of leical pri(itives+hich can !e co(!ined in varios +ays accordin" to the syntactic rles of (entalese to for( apotentially infinite variety of co(ple representations, 8st as in the case of natral lan"a"es it ispossi!le to "enerate an infinite variety of (eanin"fl tterances ot of a finite stock of (orphe(es and

co(positional rles. 2entalese is ths vie+ed as havin" the sa(e "enerative and creative aspectspossessed !y natral lan"a"es. So +hile the se(antic properties of (ental states are 7inherited7 fro(the representations they contain, those representations (ay the(selves !e either se(antically pri(itiveor co(posed ot of se(antic pri(itives !y the application of syntactic rles.

&.70

Co*nitive $ro3esses

f a representational accont of the (ind provides a +ay of interpretin" the natre of individaltho"hts, it does not itself provide any co(para!le accont of the natre of (ental processessch asreasonin" to a conclsion or for(in" and testin" a hypothesis, and hence does not provide the "ronds

for a psycholo"y of co"nition. 'or a psycholo"y of co"nition, so(ethin" (ore is needed: a theory of(ental processes that ses

5 @6 5

the properties of (ental representations as the !asis of a casal accont of ho+ one (ental statefollo+s another in a train of reasonin". Sppose, for ea(ple, that one +ishes to eplain +hy Aones hasclosed the +indo+. n eplanation (i"ht +ell !e "iven alon" the follo+in" lines:

/10 Aones felt a chill.

/@0 Aones noticed that the +indo+ +as open.

/#0 Aones hypothesiDed that there +as a cold draft !lo+in" in thro"h the +indo+.

/J0 Aones hypothesiDed that this cold draft +as the case of his chill.

/%0 Aones +anted to stop feelin" chilled.

/60 Aones hypothesiDed that cttin" off the draft +old stop the chill.

so, /-0 Aones for(ed a desire to ct off the draft.

/&0 Aones hypothesiDed that closin" the +indo+ +old ct off the draft.

so, /90 Aones for(ed a desire to close the +indo+.

so, /1$0 Aones closed the +indo+.

Here +e have not a rando( train of tho"ht, !t a se=ence of tho"hts in +hich the latter tho"hts areplasi!ly vie+ed as !oth /a0 rational in li"ht of those that have "one !efore the(, and /b0conse=ences of those previos statesAones for(ed a desire to close the +indo+ becausehe tho"htthat doin" so +old ct off the draft. 2oreover, a casal theory of inference +old need to for"e aclose link !et+een the se(antic properties of individal states and their role in the prodction ofs!se=ent states. t is chan"es in the contentof Aones?s !eliefs and desires that +e +old epect toprodce different trains of tho"ht and different !ehaviors. f Aones had noticed the fan rnnin" insteadof noticin" an open +indo+, +e +old epect hi( to entertain different hypotheses, for( different


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desires, and act in a different +ay, all as a conse=ence of chan"in" the content of his !elief fro( 7the+indo+ is open7 to 7the fan is rnnin".7

o+ C*2?s representational accont of intentional states see(s +ell sited to a discssion of thesemanticrelations !et+een intentional states, since the se(antic and intentional properties ofintentional states are identified +ith those of the representations they involve. Bt +hen it

5 @- 5

'i"re @

co(es to the =estion of ho+ intentional states can play a causalrole in the etiolo"y of a process thatinvolves the "eneration of ne+ intentional states, the notion of representation, in and of itself, has littleto offer. ie+in" intentional states as relations to representations allo+s s to locate the se(anticrelationships !et+een intentional states in relationships !et+een the representations they involve, !t itdoes little to sho+ ho+ Aones?s standin" in relation+to a representationMat ti(e tcan play a casalrole in Aones co(in" to stand in relation 1to a representationMQat tR

.

*his see(s to present a pro!le(. n order for a se=ence of representations to (ake p a rational,co"ent train of tho"ht, the =estion of 'hichrepresentations shold occr in the se=ence shold !edeter(ined !y the (eanin"s of the earlier representations. n order for the se=ence of representationsto mae sense,the later representations need to stand in appropriatesemanticrelationships to the earlierones. Bt in order for a se=ence of representations to !e a causalse=ence, the =estion of +hatrepresentations +ill occr later in the se=ence (st !e deter(ined !y the casal po+ers of the earlierrepresentations. o+ intentional eplanations pick ot representations !y their contentthat is, !ytheir se(antic properties. Bt if sch eplanations are to !e casal eplanations, they (st pick otrepresentations in a fashion that individates the( accordin" to their casal po+ers. Bt this can !edone only if the se(antic vales of representations can !e linked to, or coordinated +ith, the casalroles they can play in the prodction of other representations and the etiolo"y of !ehavior. *his has!een seen !y so(e as a si"nificant st(!lin" !lock to the possi!ility of a casal3no(olo"icalpsycholo"y, as it is notoriosly pro!le(atic to vie+ se(antic relationships as casal relationships or toe=ate reasons +ith cases.L9M *he pro!le(, then, for trnin" a representational theory of (ental statesinto a psycholo"ical theory of (ental processes is one of findin" a +ay to link the se(antic propertiesof (ental representations to the casal po+ers of those representations /see fi". @0.

5 @& 5

t is precisely at this point that the co(pter paradi"( co(es to !e of interest. 'or co(pters arenderstood as devices that store and (aniplate sy(!ol tokens, and the (aniplations that theyperfor( are dependent pon +hat representations are already present, yet they are also co(pletely(echanical and ncontroversially casal in natre. 2achine co(ptation provides a "eneral paradi"(for nderstandin" sy(!ol3(aniplation processes in +hich the sy(!ols already present play a casalrole in deter(inin" +hat ne+ sy(!ols are to !e "enerated. C*2 seeks to provide an etension of this


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paradi"( to mentalrepresentations, and there!y to spply an accont of co"nitive processes that canprovide a +ay of discssin" their etiolo"y +hile also respectin" the se(antic relationships !et+een therepresentations involved.

&.(0

!ormali8ation and Computation

C*2?s advocates !elieve that (achine co(ptation provides a paradi"( for nderstandin" ho+ onecan have a sy(!ol3(aniplatin" syste( that can causederivations of sy(!olic representations in afashion that 7respects7 their se(antic properties. 2ore specifically, (achine co(ptation is !elieved toprovide ans+ers to t+o =estions: /10 Ho+ can se(antic properties of sy(!ols !e linked to casalpo+ers that allo+ the presence of one sy(!ol tokens1at ti(e t to !e a partial case of the tokenin" of

a second sy(!ols@at ti(e tR

nd /@0 ho+ can the la+s "overnin" the casal re"larities also assre that the operations that "enerate

ne+ sy(!ol tokens +ill 7respect7 the se(antic relationships !et+een the sy(!ols, in the sense that theoverall process +ill trn ot to !e, in a !road sense, rationalK

*he ans+ers that C*2?s advocates +old like to provide for these =estions can !e developed in t+osta"es. 'irst, +ork in the for(aliDation of sy(!ol syste(s in nineteenth3 and t+entieth3centry(athe(atics has sho+n that, for s!stantial /al!eit li(ited0 interpreted sy(!olic do(ains /sch as"eo(etry and al"e!ra0, one can find +ays of carryin" ot valid derivations in a fashion that does notdepend pon the (athe(atician?s intition of the (eanin"s of the sy(!ols, so lon" as /a0 the se(anticdistinctions !et+een the sy(!ols are reflected !y syntactic distinctions, and /b0 one can develop aseries of rles, dependent +holly pon the syntactic featres of sy(!ol strctres, that +ill licensethose dedctions and only those dedctions that one +old +ish to have licensed on the !asis of the(eanin"s of the ter(s. Second, di"ital co(pters are devices that store and (aniplate sy(!olic

representations.

5 @9 5

*heir 7(aniplation7 of sy(!olic representations, (oreover, consists in creatin" ne+ sy(!ol tokens,and the re"larities that "overn +hat ne+ tokens are to !e "enerated (ay !e cast in the for( ofderivation3licensin" rles !ased pon the syntactic featres of the sy(!ols already tokened in co(pterstora"e. n a co(pter, sy(!ols play casal roles in the "eneration of ne+ sy(!ols, and the casal rolethat a sy(!ol can play is deter(ined !y its syntactic type. 'or(aliDation sho+s that /for li(iteddo(ains0 the se(antic properties of a set of sy(!ols can !e 7(irrored7 !y syntactic properties di"italco(pters offer proof that the syntactic properties of sy(!ols can !e casal deter(inants in the"eneration of ne+ sy(!ols. ll in all, the co(pter paradi"( sho+s that one can coordinate these(antic properties of representations +ith the casal roles they (ay play !y encodin" all se(anticdistinctions in synta.

*hese crcial notions offormali*ationand computation+ill no+ !e discssed in "reater detail. *hesenotions are, no do!t, already fa(iliar to (any readers. Ho+ever, ho+ one tells the story a!ot thesenotions si"nificantly inflences the conclsions one is likely to dra+ a!ot ho+ they (ay !e e(ployed,and so it see(s +orth+hile to tell the story ri"ht fro( the start.


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&.(.&0

!ormali8ation

n the second half of the nineteenth centry, one of the (ost i(portant isses in (athe(atics +as theformali*ationof (athe(atical syste(s. *he for(aliDation of a (athe(atical syste( consists in theeli(ination fro( the syste(?s dedction rles of anythin" dependent pon the (eanin"s of the ter(s.'or(aliDation !eca(e an i(portant isse in (athe(atics after 4ass, Bolyai, >o!achevski, andGie(ann independently fond consistent "eo(etries that denied )clid?s parallel postlate. *his led toa desire to relieve the procedres e(ployed in (athe(atical dedctions of all dependence pon these(antic intitions of the (athe(atician /for ea(ple, her )clidean spatial intitions0. *he process offor(aliDation fond a definitive spokes(an in ;avid Hil!ert, +hose !ook on the fondations of"eo(etry, p!lished in 1&99, e(ployed an approach to aio(atiDation that involved a co(pletea!straction fro( the (eanin"s of the sy(!ols. *he for(aliDation of lo"ic, (ean+hile, had !eenndertaken !y Boole and later !y 're"e, Whitehead, and Gssell, and the for(aliDation of arith(etic !yPeano.

While there +ere several different approaches to for(aliDation in nineteenth3centry (athe(atics,Hil!ert?s 7sy(!ol3"a(e7 approach is of

5 #$ 5

special interest for or prposes. n this approach, the sy(!ols sed in proofs are treated as tokens orpieces in a "a(e, the 7rles7 of +hich "overn the for(ation of epressions and the validity ofdedctions in that syste(. *he rles e(ployed in the sy(!ol "a(e, ho+ever, apply to for(lae onlyinsofar as the for(lae fall nder particlarsyntactictypes. *his ideal of for(aliDation in a(athe(atical do(ain re=ires the a!ility to characteriDe, entirely in notational /sy(!olic and syntactic0ter(s, /a0 the rles for +ell3for(edness of sy(!ols, /b0 the rles for +ell3for(edness of for(las, /c0the aio(s, and /d0 the rles that license derivations.

What is of interest a!ot for(aliDa!ility for or prposes is that, for li(ited do(ains, one can find(ethods for prodcin" derivations that respect the (eanin"s of the ter(s !t do not rely pon the(athe(atician?s kno+led"e of those (eanin"s, !ecase the (ethod is !ased solely pon their syntacticfeatres. *hs, for ea(ple, a lo"ician (i"ht kno+ a derivation3licensin" rle to the effect that,+henever for(las of the for(pandp2qhave !een derived, he (ay validly derive a for(la of thefor( q. *o apply this rle, he need not kno+ the interpretations of any of the s!stittion instances ofpand q, or even kno+ +hat relation is epressed !y2, !t need only !e a!le to reco"niDe sy(!olstrctres as havin" the syntactic for(spandp2q. s a conse=ence, one can carry ot rational,sense3 and trth3preservin" inferences +ithot attendin" toor even kno+in"the (eanin"s of theter(s, so lon" as one can devise a set of syntactic types and a set of for(al rles that captre all of these(antic distinctions necessary to license dedctions in a "iven do(ain.

&.(.20

" 1at)emati3al Notion o+ Computation

second isse arisin" fro( trn3of3the3centry (athe(atics +as the =estion of +hat fnctions are7co(pta!le7 in the sense of !ein" s!8ect to evalation !y the application of a rote procedre oral"orith(. *he procedres learned for evalatin" inte"rals are "ood ea(ples of co(ptationalal"orith(s. >earnin" inte"ration is a (atter of learnin" to identify epressions as (e(!ers of particlarsyntactically characteriDed classes and learnin" ho+ to prodce the correspondin" epressions that


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indicate the vales of their inte"rals. Ene learns, for ea(ple, that inte"rals +ith the for(

have soltions of the for(

, and so on.Sch co(ptational (ethods areformal,in the sense that a person?s a!ility to apply the (ethod doesnot re=ire any nderstandin" of the

5 #1 5

(eanin"s of the ter(s.L1$M *o evalate

, for ea(ple, one need not kno+ +hat the epression indicatesthe area nder a crve!t only thatit is of a particlar syntactic type to +hich a particlar rle for inte"ration applies. Si(ilarly, one (i"htapply the techni=es sed in col(n addition /another al"orith(ic procedre0 +ithot kno+in" +hatn(!ers one +as addin". 'or ea(ple, one (i"ht apply the (ethod +ithot lookin" to see +hatn(!ers +ere represented, or the n(!ers (i"ht !e too lon" for anyone to reco"niDe the(. Ene (i"hteven learn the rles for (aniplatin" di"its +ithot havin" !een told that they are sed in therepresentation of n(!ers. *he (ethod of col(n addition is so desi"ned, in other +ords, that thereslts do not depend pon +hether the person perfor(in" the co(ptation kno+s the (eanin"s of theter(s. *he procedre is so desi"ned that applyin" it to representations of t+o n(!ers Aand%+illdependa!ly reslt in the prodction of a representation of a n(!er Csch thatAR% C.

&.(.40T)e S3ope o+ !ormal Symbol91anipulation Te3)ni:ues

t trns ot that for(al inference techni=es have a srprisin"ly +ide scope. n the nineteenth and earlyt+entieth centry it +as sho+n that lar"e portions of lo"ic and (athe(atics are s!8ect tofor(aliDation. nd this is tre not only in lo"ic and n(!er theory, +hich so(e theorists hold to !edevoid of se(antic content, !t also in sch do(ains as "eo(etry, +here the ter(s clearly haveconsidera!le se(antic content. Hil!ert /1&990, for ea(ple, de(onstrated that it is possi!le tofor(late a collection of syntactic types, aio(s, and derivation3licensin" rles that is rich eno"h tolicense as valid all of the "eo(etric derivations one +old +ish for on se(antic "ronds +hileecldin" as invalid any derivations that +old !e eclded on se(antic "ronds.

Si(ilarly, (any pro!le(s lyin" otside of (athe(atics that involve hi"hly contet3specific se(anticinfor(ation can !e "iven a for(al characteriDation. "a(e sch as chess, for ea(ple, (ay !erepresented !y /10 a set of sy(!ols representin" the pieces, /@0 epressions representin" possi!le statesof the !oard, /#0 an epression pickin" ot the initial state of the !oard, and /J0 a set of rles "overnin"the le"ality of (oves !y (appin" epressions representin" le"al states of the !oard after a (ove mtothe set of epressions representin" le"al sccessor states after (ove mR 1. So(e "a(es, sch as tic3tac3toe, also ad(it of al"orith(ic strate"ies that assre a +innin" or nonlosin" "a(e. n addition to"a(es, it is


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short, *rin" sho+ed that it is possi!le to link synta to casal po+ers in a co(ptin" (achine.

computing machineis a device that possesses several distinctive featres. 'irst, it contains (edia in+hich sy(!olic representations can !e stored. *hese sy(!ols, like +ritten sy(!ols, can !e arran"edinto epressions havin" syntactic strctres and (ay !e assi"ned interpretations thro"h aninterpretation sche(e. Second, a co(pter is capa!le of differentiatin" !et+een representations in afashion correspondin" to distinctions in their syntactic 7shape.7 *hird, it can case the tokenin" of ne+

representations. 'inally, the casal re"larities that "overn 'hatne+ sy(!ols the co(pter +ill caseto !e tokened are dependent upon the syntactic formof the sy(!ols already stored !y the (achine.

*o take a si(ple ea(ple, sppose that a co(pter is pro"ra((ed to sa(ple t+o stora"e locationsAand%+here representations of inte"ers are stored and to case a tokenin" of a representation at a third

5 #J 5

location Cin sch a fashion that the representation tokened at C+ill !e a representation of the s( ofthe t+o n(!ers represented atAand%. *he representations fond atA,%, and Chave syntacticstrctre: let s ass(e that each representation is a series of !inary di"its /1s and $s0. *hey also have

se(antic interpretations: na(ely, those assi"ned to the( !y the interpretation sche(e e(ployed !y thedesi"ner of the pro"ra(. o+ +hen the co(pter eectes the pro"ra(, it +ill case the tokenin" of arepresentation at C. Ast 'hatrepresentation is tokened at C+ill depend pon +hat representations arefond atAand%. 2ore specifically, it +ill depend pon thesyntactic typeof the representations fondatAand%na(ely, pon +hat se=ences of !inary di"its are present at those locations. What theco(pter does in eectin" this pro"ra( is ths analo"os to the application of a for(al al"orith(/sch as that e(ployed in col(n addition0, +hich is sensitive to the syntactic for(s of therepresentations atAand%. f the pro"ra( has !een properly desi"ned, the overall process +illaccrately (i(ic addition as +ell, in the sense that +hat is tokened at C+ill al+ays !e a representationof the s( of the t+o n(!ers represented atAand%. *hat is, if the pro"ra( is properly desi"ned, thesyntactically dependent operations perfor(ed !y the (achine +ill ensre the prodction of a

representation at Cthat !ears the desired se(antic relations to the representations atAand%as +ell.L11M *he se(antic properties of the representations play no casal role in the processthey areetiolo"ically inert. Bt since all se(antic distinctions are preserved syntactically, and syntactic typedeter(ines +hat a representation can contri!te casally, there is a correspondence!et+een arepresentation?s se(antic properties and the casal role it can play.

*his ea(ple illstrates three salient points. *he first is the insi"ht !orro+ed fro( for(al lo"ic and(athe(atics that at least so(e se(antic relations can !e reflected or 7tracked7 !y syntactic relations.*he second is the insi"ht !orro+ed fro( co(pter science that (achines can !e (ade to operate ponsy(!ols in sch a +ay that the syntactic properties of the sy(!ols can !e reflected in their casal roles.ndeed, for any pro!le( that can !e solved !y the application of a for(al al"orith( A, it is possi!le todesi"n a (achineMthat +ill "enerate a series of representations correspondin" to those that +old !e

prodced !y the application of al"orith(A. *hese t+o points 8ointly yield a third: na(ely, that it ispossi!le for (achines to operate pon sy(!ols in a +ay that is, in 'odor?s +ords, 7sensitive solely tosyntactic properties7 of the sy(!ols and 7entirely confined to alterin" their shapes,7 +hile at the sa(eti(e

5 #% 5


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'i"re J

the (achine is so devised that it +ill transfor( one sy(!ol into another if and only if the propositionsepressed !y the sy(!ols that are so transfor(ed stand in certain se(antic relationse.".,the relation that the pre(ises !ear to the conclsion of a valid ar"(ent. /'odor 19&-: 190

n !rief, 7co(pters sho+ s ho+ to connect se(antical +ith casal properties for symbols7 /i!id.0.nd this co(pletes the desired linka"e !et+een se(antics and casality: for do(ains that can !efor(aliDed, se(antic properties can !e linked to casal properties !y encodin" se(antic differences insynta and desi"nin" a (achine that is driven !y the syntactic featres of the sy(!ols /see fi". J0.

&.;0

T)e Computational "33ount o+ Co*nitive $ro3esses

We have seen that the first thesis co(prisin" C*2 +as a representational accont of the natre of

intentional states: na(ely, that sch states are relations to (ental representations. *he second thesisco(prisin" C*2 is a co(ptational accont of the natre of co"nitive processes: na(ely, thatco"nitive processes are computations o"er mental representations,or 7casal se=ences of tokenin"s of(ental representations7 /'odor 19&-: 1-0. 'odor +rites,

train of tho"hts, for ea(ple, is a casal se=ence of tokenin"s of (entalrepresentations +hich epress the propositions that are the o!8ects of the tho"hts. *o a firstapproi(ation, to think ?t?s "oin" to rain so ?ll "o indoors? is to have a tokenin" of a(ental representation that (eansI$ll go indoorscased, in a certain +ay, !y a tokenin" of a(ental representation that (eansIt$s going to rain. /i!i

computational theory mind

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