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Philosophical Review Computation and Content Author(s): Frances Egan Source: The Philosophical Review, Vol. 104, No. 2 (Apr., 1995), pp. 181-203 Published by: Duke University Press on behalf of Philosophical Review Stable URL: http://www.jstor.org/stable/2185977 . Accessed: 17/02/2011 14:54 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=duke. 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Introduction The dominant program in cognitivepsychology since the demise of behaviorismin the 1960s has been computationalism.Computa- tional theories treat human cognitiveprocesses as a species of in- formationprocessing, and the systemsthat implement such pro- cessing as symbol-manipulatingsystems. Describing a device as a symbolmanipulator implies that it is possible to treat some of its internal statesas representationsof propertiesor objects in a par- ticulardomain. Computational theoriesof vision,for example, pos- it internal states that can be interpretedas representingthe depth of the distal scene. There has been considerable disagreementabout the nature and functionof representationalcontents assigned to the statesposited by computational theories. It is widelythought that such theories respect whatJerry Fodor (1980) has called the "formalitycondi- tion," which requires that computational processes have access only to the formal (that is, nonsemantic)properties of the repre- sentationsover which theyare defined. It is by respectingthe for- malitycondition that computationalismpromises to answerone of the most pressingproblems in the philosophy of mind-how can representationalmental states be causally efficaciousin the pro- duction of behavior? Representationalmental states,according to computationalism,have their causal roles in virtue of (roughly) their structuralproperties.' But this advantage comes at a price. The formal character of computational description appears to leave no real workfor the semanticproperties of the mental states it characterizes.Thus, computationalismhas been thoughtby some to support a form of eliminativism,the thesis that denies that in- tentionallycharacterized states play a genuinely explanatoryrole in psychology (see, for example, Stich 1983). If the content of computationalstates is indeed explanatorilyidle, then the relation 'For language-likerepresentations, the formalitycondition claims that theyhave theircausal roles in virtueof their syntax. 181 FRANCESEGAN between psychological states, as characterized by computational psychology,and psychologicalstates as characterizedby our com- monsense explanatory practices, which do advert to content, is quite obscure. In this paper I articulateand defend a strategyfor reconciling the formal characterof computational descriptionwith a commit- ment to the explanatoryusefulness of mental content.I argue that content does not play an individuativeor taxonomic role in com- putational theories-a computationalcharacterization of a process is a formalcharacterization. Nonetheless, content does play a gen- uine explanatoryrole in computational accounts of cognitiveca- pacities. Content ascriptionsconnect the formal characterization of an internalprocess withthe subject's environment,enabling the computationaltheory to explain how the operation of the process constitutesthe exercise of a cognitivecapacity in thatenvironment. I support my account of the role of content in computationalpsy- chology by reference to David Marr's theory of early vision,2in part because it has received a great deal of attentionfrom philos- ophers; however,my argument depends on general features of computational methodology,and so applies to computational the- ories generally. Recent attemptsto reconcile computationand content have ap- pealed to a notion of narrowcontent, that is, content that super- venes on intrinsicphysical states of the subject. Proponents of nar- row content have so far failed to articulatea notion that is clearly suitable for genuine explanatorywork in psychology.3I argue that it is typicallybroad content that plays a central role in computa- tional explanation, though I do identifya specific (and limited) functionserved by narrow content ascription. 2. Why ComputationalTheories Are Not Intentional It might be argued that, the formalitycondition notwithstanding, computational theories are intentionalin the followingsense: The 2For the most detailed exposition of Marr's theorysee Marr 1982. 3Loar (1988) and Segal (1989, 1991) have perhaps come closest. Loar's proposal concerns commonsense, as opposed to computational,psychol- ogy.Segal argues thatnarrow content plays a centralrole in Marr's theory. See Egan (forthcoming)for criticismof Segal's proposal. 182 states they posit not only have representationalcontent, but the contentthey have playsan individuativerole in the theory.In other words, computational theories taxonomize states by reference to their contents. The motivationfor the claim thatcomputational theories of cog- nition are intentionalin the above sense is not hard to understand. Consider the followingpassages: Thereis no otherway to treatthe visual system as solvingthe problem thatthe theorysees it as solvingthan by attributing intentional states thatrepresent objective physical properties. (Burge 1986, 28-29) [I]t is at leastarguable that where rational capacities are the explan- anda, it is necessarythat there be propositionalattitudes in the ex- planans.If thisargument is correct,then it is pragmaticallyincoherent forStich and his followersto insistthat cognitive psychology explains rationalcapacities by referenceto statesnot describedas possessing propositionalcontent. (Hannan 1993,173) The argument underlyingboth passages can be expressed some- what crudelyas follows: (P) The explananda of computational psychological theories are intentionallycharacterized capacities of subjects. (C) Therefore,computational psychological theories are inten- tional-they posit intentionalstates. Underlyingthe argument is the intuition that scientificexpla- nations should "match" (in some sense) theirexplananda. Wilson endorses a constraintof this sort, which he calls theoreticalappro- priateness: An explanation is theoreticallyappropriate when it providesa natural (e.g. non-disjunctive)account of a phenomenon at a level of expla- nation matchingthe level at which thatphenomenon is characterized [in the explanandum]. (1994, 57) The notion of a "level of explanation" is somewhat vague, but let us assume, for the sake of argument, that there is a unique level of explanation such that all and only explanations at that level involve ascriptions of content. If theoretical appropriateness is a desideratum of scientific explanation, then an explanation of in- 183 FRANCESEGAN tentionallycharacterized phenomena should itselfadvert to inten- tionallycharacterized states.4 An unresolved tension surfaces,though, when we consider com- putational explanation. The fact that the explananda of computa- tional theories are intentionallyspecified suggests that computa- tional statesare essentiallyindividuated by referenceto their con- tents.If computational theories are not intentional,then how can computational theories explain intentionallycharacterized phe- nomena? But the formalitycondition exerts an opposite pressure. In requiring that computational processes have access only to the nonsemantic properties of the representationalstates over which they are defined, it suggests that computational individuationis nonsemantic,or in Fodor's terminology,formal. Are computational taxonomies intentionalor formal?At thispoint it is helpfulto turn to a well-developedexample. Interpretersof Marr's theoryof vision have assumed that visual statesare individuatedin the theoryby referenceto theircontents, hence thatthe theoryis intentional(see Burge 1986; Kitcher1988; Segal 1989, 1991; Davies 1991; Morton 1993; Shapiro 1993). Al- though there has been a good deal of disagreementabout the sort of content (broad or narrow) that Marrian structureshave, the assumption that content plays an individuativerole in the theory has not been thought to require explicit argument.5Burge says that it is "sufficientlyevident" that the theoryis intentionalfrom the factthat "the top levels of the theoryare explicitlyformulated in intentionalterms" (1986, 35).