(ebook)(philosophy of mind) jerry a. fodor - modularity of mind-chap5

8/11/2019 (eBook)(Philosophy of Mind) Jerry a. Fodor - Modularity of Mind-chap5

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Central Systems 119

I am , heaven knows , not about to set up as an expert on neuro -

psychology , and I am painfully aware how impressionistic this all

is . But while we ' re collecting impressions , I think the following

one is striking . A recent issue of Scientific American ( September ,

1979 ) was devoted to the brain . Its table of contents is quite as

interesting as the papers it contains . There are , as you might expect ,

articles that cover the neuropsychology of language and of the

perceptual mechanisms . But there is nothing on the neuropsy -

chology of thought - presumably because nothing is known about

the neuropsychology of thought . I am suggesti ng that there i s a

good r eason why nothing is known about it - namely , that there

is nothing to know about it . You get form / function correspondence

for the modular processes ( specifically , for the input systems ) ; but ,

in the case of central processes I you get an a pproxima tion to uni -

versal connectivity , hence no stable neural architecture to write

Scientific American articles about .

To put these claims in a nutshell ; there are no content - specific

central processes for the performance of which correspondingly

specific neural structures have been identified . Everything we now

know i s compatible with the claim that central problem - solving is

subserved by equipotential neural mechanisms . This is precisely

what you would expect if you assume that the central cognitive

processes are largely Quineian and isotropic .

PART V

CA VEA TS AND CONCLUSIONS

We now have before us what might be called a ' modified ' modularity

theory of cognitive processes . According to this theory , Gall was

right in claiming that there are vertical faculties ( domain specific

computational mechanisms ) . Indeed , a still stronger claim is plau -

s ib le : t ha t t he ve rt ic al f acu lti es a re mo du le s ( i nfo rm ati on al ly e n -

capsulated , neurologically hardwired , innately specified and so

forth ) . But nonmodular cognitive systems are also acknowledged ,

and it is left open that these latter may exhibit features of horizontal

organization . Roughly speaking , on this account , the distinction

b etw ee n v ert ic al a nd h or iz on ta l m od es o f c omp ut ati on al o rg an i -

zation is taken to be coextensive with the functional distinction


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systems

Given all of this" what I propose to do in the discussion thatfollows is to consider how this general View bears on some epis-temological and methodological issues hat have recen l y got tangledup with issues about modularity . And I want to make a couple ofgloomy remarks about the implications of the modified modularitythesis for the practical prospects of cognitive science.

For purposes of the following discussion, let's forget that themodularity theory we have actually adopted is the modified one.Suppose" then, that Gall had been entirely right and the mind

proved to be exhaustively a bundle of vertical faculties. Certainrather striking epistemological consequences would then seem tobe entrained. Modular systems are, by definition special purposecomputational mechanisms. If the mind is a collection of suchmechanisms, then there are presumably going to be at least somepurposes for which the mind isn't fit . Specifically, if each 'mentalorgan' is pretuned to the solution of computational problems witha specific sort of structure" then it is surely in the cards that there

should be some problems whose structure the mind has no com-putational resources for coping with . Perhaps, indeed, there aresome important problems of which this is true. For example, it isentirely compatible with a modularity theory that there should beendogenously determined constraints on our mental capacities suchthat the best science the true theory of the structure of the world -is not one of the theories that we are capable of entertaining . Letus have a name for this thesis: I will say that a psychological theory

represents the mind as epistemically bounded f it is a consequenceof the theory that our cognitive organization imposes epistemicallysignificant constraints on the beliefs that we can entertain.

The point of present interest is that the (plausible) claim that themodularity thesis mplies epistemic boundedness has ed to a certainamount of irrelevant criticism of the former doctrine. In particular,the way the discussion in the literature has gone has made it seemthat the dispute between the modularity theory and its antagonists

is a dispute between epistemic optimism and epistemic despair.The prevalent picture seems to be this : If the mind is modular,then, in all likelihood , we are epistemically bounded; whereas if ,by contrast, God has endowed us with some form of general hence

that subserve he

120 Modularity of Mind

between systems of in pu analysis andfixa tion of belief.


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Caveats and Conclusions 121

nonmodular ) intelligence, then there is perhaps no endogenouslydetermined bound upon the class of truths that we can aspire toknow . We may fail to find the true science or, as t were, exogenousreasons; because for example, our spatiotemporal situation in theuniverse precludes access o the crucial data. But at least there isno enemy within the gates. If we don't succeed that is not becausewe were built to fail .

This is very moving , but it is also quite beside the point . It issimply a mistake to suppose that if intelligence is general in thesense of being nonmodular then it somehow follows (or even issomehow rendered plausible) that we are epistemically unbounded.In fact, I strongly suspect that the notion of epistemic unbound -edness s just incoherent whatever view you take of the modularityissues (so long as one is assuming a Realist interpretation of scienceand a correspondence theory of truth ). This all requires somediscussion.

Let us retreat to the high ground where all systems that performnondemonstrative inferences, modular or otherwise, fall togetheras hypothesis projecting/ confirming devices. It was implicit in ourearlier discussion that such a system must have access at a min -imum , to:

(a) A source of hypotheses to be (dis)confirmed.(b) A data base(c) A metric which can compute the confirmation level of agiven hypothesis relative to a given data base.

Consider, now , how such a device might be so organized that itfails, in virtue of features of its organization, to pick the best hy-pothesis for the available data.

There are, to begin with , boring possibilities associated with par-ametric limitations of one sort or another. One could imagine thatthe computation that would select the right hypothesis is too longfor the system to perform given available resources of memory,attention, etc.; or that the hypothesis that expresses he best hy-pothesis contains too many clauses (in canonical notation) for thedevice to parse; or that the critically relevant data base s too complexfor the device to represent . . . etc. I suppose that even the moststarry-eyed epistemic optimist would accept the sort of epistemicboundedness implicit in these kinds of limitations . Even if , to para-


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phrase Putnam (1980, p. 298), 'God chose, instead of packing ourheads with a billion different mental organs, simply to make ussmart', it is surely conceivable that he failed to make us smartenough Perhaps solving the riddle of the universe requires onemore neuron than , de facto , anyone will ever have . Sad , of course ,

but surely not out of the question. So I shall take it to be commonground that epistemic boundedness arising from these sorts ofquantitative limitations on our cognitive capacities is compatiblewith the view that intelligence is general - i .e., not only with themodularity theory but with its denial .

Now letis consider some other ways in which a hypothesis-testing system could prove to be epistemically bounded; kinds oflimitations that may seem to be more intimately connected withmodularity per set There are, in particular , two of these: modularsystems may be supposed to be constrained in respect of the classof hypotheses o which they have access and in respect of the bodyof data that can be consulted in the evaluation of any given hy-pothesis. The latter, according to our analysis, is a constraint thatis specific to modular systems, since it is just a way of formulatingthe notion of informational encapsulation; and we have seen thatit is primarily informational encapsulation that makes a systemmodular . Contrapositively , when we imagine a system of generalintelligence , we are imagining a mechanism that is informationallyunencapsulated; one in which any of the available data may bebrought to bear on any of the hypotheses that it can entertain.Question: is an i:ntelligence that is nonmodular in that sense- aninformationally unencapsulated system- ipso facto epistemicallyunbounded ?

Answer : no . The obvious reason is that epistemic unboundednessis primarily an issue about domain specificity and not about infor -mational encapsulation. What epistemic unboundedness requiresis that the exercise of intelligence should not be biased towardssome kinds of problems to the exclusion of others; more generally,that there should be no interesting endogenous constraints on thehypotheses accessible o intelligent problem-solving . A psychologywhich guarantees our epistemic unboundedness would thus haveto guarantee that, whatever sort of subject domain the world turnsout to be, somewhere n the space of hypotheses hat we are capableof entertaining there is the hypothesis that specifies its structure.


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My present point is that the denial of the modularity thesis doesnot guarantee this; indeed, I don't see how any remotely plausiblecognitive theory could conceivably do so. It is, in any event, patentlya fallacy to suppose that since the modularity thesis implies bound -edness, the way to get unboundedness is to deny the modularitythesis .

A good way to see what is going on here is to notice that, his-torically , the most nonmodular psychologies that have been pro-posed have nevertheless been compatible with - indeed, haveentailed - very extreme versions of the boundedness thesis . Con -

sider, e.g., the associationism of a philosopher like Hume. OnHume ' s view , the mind has no intrinsic architecture whatever

(Hume says that the play of Ideas is like a play in a theater-except that there is no theater ). There are no faculties ; mental struc -ture is reduced to parameters of association as per the discussionin Part I of this essay. And since any Idea can, in principle , becomeassociated with any other, you have in Hume's psychology some-thing like the ultimate in nonmodular theories of mind .

But do you have epistemic unboundedness ? Not on your NellyIn fact , the class of beliefs that can be entertained according toHume's account is perhaps more sharply delimited than any mod-ularity theorist has ever proposed. This is because the class ofaccessible beliefs is determined by the class of accessible concepts;and , for Hume , the class of accessible concepts is determined bythe Empiricist principle ; there are no concepts except such as canbe constructed from sensations. So, in particular , if the hypothesesof the best science would be such as to make reference to God , or

to electrons, or to triangles, or to mental faculties, or to any otherunobservables, then the best science is humanly inaccessible onHume's account; it is beyond the epistemic bounds that Humeposits . Moreover , and this is the consideration that cuts ice, itsinaccessibility is a consequence of the (presumed) character of hu-man psychology; if Hume is right , then it is the ontogeny of ourconcepts that precludes our having a science n which reference tounobservables figures ineliminably .

Of course , this isn ' t the way that Hume understood the epis-temological consequences of his psychological views. Hume cer-tainl y does not take himself to be espousing a form of theboundedness thesis. But that is because of some extrapsychological



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(roughly , semantic) theses that Hume also endorses. Hume holdsmore or less explicitly (and later Empiricists held absolutely ex-plicitly ) that the Empiricist principle provides a criterion of cognitivesignificance. The best science couldn't include hypotheses aboutGod (electrons, triangles, faculties, etc.) because such hypothesesare not just psychologically inaccessible ut also semantically empty.Talk about God couldn't figure in a true science because alk aboutGod is meaningless.

The point of all this is that it 's not his associationism (his non-modularity ) that buys Hume epistemic unboundedness; associationism is compatible with the most stringent constraints on thepsychologically accessible beliefs. What buys Hume epistemic un-boundedness is the Empiricist theory of meaning a semantic thesisthat has the convenient property of entailing that the psychologicallyinaccessible beliefs are ipso facto nontruth -valuable. If one givesup the Empiricist theory of meaning (as one must, because t issurely false), then one sees with dramatic clarity how little of ep-istemic unboundedness psychological nonmodularity actuallyguarantees.

The idea of attacking epistemic boundedness with semantic hesesis, of course, still with us; for recent versions, see Davidson (1973- 4)and Rorty (1979). My own view, for what it 's worth , is that allsuch proposals are ineliminably verificationistic and hence inde-fensible. Very roughly , the available options seem to ~ome in twoclusters. Either one has the unintelligibility of boundedness at theprice of a verificationist semantics, a coherence heory of truth and,eventually , an Idealist ontology ; or one opts for Realism and cor-respondence at the price of making boundedness an empirical issue.I think that the second strategy is certainly the right one, but it isworth emphasizing that, in a certain sense the modularity theory-even in a comprehensive version like Gall 's- is not in jeopardyon either account. Suppose that some form of verificationism istrue and we can make no sense of the possibility that the bestscience might be expressible only by hypotheses that are psycho-logically inaccessible to us. It could then hardly be an objection to

the modularity thesis that if that possibility were intelligible , themodularity thesis would leave it open.

One way to get unboundedness is thus via the (slightly Pyrrhic)demonstration that its denial is unintelligible . (Slightly Pyrrhic be-


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cause one is tugged by the view that if -P is unintelligible , then Pmust be too.) Suppose, however, that we eschew that route andassume that the issues about epistemic boundedness are empirical(though, of course, very abstractly related to data). It then seemsto me hard to see how the unboundedness view can be madeempirically plausible . The point is that any psychology must at-tribute some endogenous structure to the mind (really unstructuredobjects- bricks, say- don' t have beliefs and desires and they don' tlearn things). And it 's hard to see how , in the course of makingsuch attributions of endogenous structure, the theory could fail toimply some constraints on the class of beliefs that the mind canentertain.42 These considerations hold quite independent of issuesabout modularity ; they suggest a sense n which any theory of themind must endorse its domain specificity. The only epistemolog-ically interesting question would thus be how likely it is that someof the inaccessible thoughts are both interesting and true.

But I don't suppose that such reflections are conclusive. Perhaps,after all , someone will some day make serious sense of an un-boundedness thesis. Suffice it for present purposes to claim thatnobody has been able to do so to date. All cognitive psychologiesthus far proposed, modular or otherwise, imply boundedness; andsome of the least modular psychologies imply some of the mostdrastic epistemic bounds. To repeat: when unboundedness has beendefended, in the historical tradition , it has typically been on semanticrather than psychological grounds; and the semantic assumptionsfrom which unboundedness was inferred were, in my view, uni-formly not good.

If , in short, your main reason for believing in general intelligenceis that you would like it to turn out that we are epistemicallyunbounded , then you might as well accept the modularity thesisfor all the good that its denial is likely to do you . Even if cognitiveprocesses are assumed to be uniformly Quineian and isotropic-hence utterly unencapsulated- the main argument for epistemicboundedness is still in force: so long as the class of accessibleconcepts is endogenously constrained, there will be thoughts that

we are unequipped to think . And , so far, nobody has been able todevise an account of the ontogeny of concepts which does notimply such endogenous constraints. This conclusion may seem essunbearably depressing if one considers that it is one that we un-

Caveats nd Conclusions 25


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hesitatingly accept for every other species One would presumablynot be impressed by a priori arguments in tended to prove (e. g.)that the true science must be accessible o spiders.

I promised a parting word or two about what the prospects forresearch n cognitive science might be like assuming that the mod-ified modularity thesis is true. My point will be this: the limits ofmodularity are also likely to be the limits of what we are going tobe able to understand about the mind , given anything like thetheoretical apparatus currently available.

Coextensions, of one sort or another, have been the burden ofmy plaint throughout . I have suggested that the functional dis-tinction between input analysis and the fixation of belief dividescognitive processes at the same point as the architectural distinctionbetween vertical and horizontal faculties; and that the distinctionbetween vertical and horizontal faculties corresponds, in turn , tothe distinction between relatively local and relatively global com-putations . I now add that these distinctions also demarcate theareas n which research n cognitive science has encountered somereasonable amount of success over the last twenty years or so, fromthose in which the failure has been pretty nearly absolute. Whilesome inter~sting things have been learned about the psychologyof input analysis- primarily about language and vision- the psy-chology of thought has proved quite intractable.

In particular , on my view , the attempt to develop general modelsof intelligent problem-solving- which one associates most closelywith work in artificial intelligence by such figures as Schank, Min -

sky, Newell , Winograd, and others- has produced surprisingly littleinsight despite the ingenuity and seriousness with which it hasoften been pursued. I have the impression that it is becoming rathergenerally conceded that this early, as one might say Wagnerian,phase of AI research has led to a dead end, and that the directionof current interest is increasingly the simulation of relatively en-capsulated processes associated with perception and language. Vi -sion (Ullman , 1979), visual imagery (Kosslyn, 1980), and machine

parsing are thus current loci of considerable activity ; enthusiasmfor a frontal assault on central processes for literally building anintelligent machine- seems to have considerably abated.

What happened in much of the earlier work could be described


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as an (implicit ) attempt to treat central processes as though theywere modular . Intellectual capacities were divided into what seem,in retrospect, to be quite arbitrary subdepartments (proving theo-rems of elementary logic; pushing blocks around; ordering ham-burgers), and the attempted simulations proceeded by supplyingmachines with very large amounts of more or less disorganized,highly topic-specific facts and heuristics. The result was an accountof central processes which failed to capture precisely what is mostinteresting about them: their wholism , what we have been callingtheir Quineianism and isotropy . What emerged was a picture ofthe mind that looked rather embarrassingly like a Sears catalogue.43

Precisely analogous remarks hold for cognitive science outsideAI . What has been reasonably successfully developed is a sort ofextended psychophysics. A lot is known about the transformationsof representations which serve to get information into a form ap-propriate for central processing; practically nothing is known aboutwhat happens after the information gets there. The ghost has beenchased further back into the machine, but it has not been exorcised.

I won 't argue for this evaluation of the present state of the art;I am fully aware that it 's tendentious. What I do want to argue foris this : if the modified modularity theory is true, it is not unintel -ligible that our successes nd failures should have been distributedin the way I've just described. Specifically, if central processes havethe sorts of properties that I have ascribed to them, then they arebad candidates for scientific study.

One relatively minor reason is this . We have seen that isotropicsystems are unlikely to exhibit articulated neuroarchitecture. If , asseems plausible, neuroarchitecture is often a concomitant of con-straints on information flow , then neural equipontentiality is whatyou would expect in systems in which every process has more orless uninhibited access o all the available data. The moral is that,to the extent that the existence of form/ function correspondenceis a precondition for successful neuropsychological research thereis not much to be expected in the way of a neuropsychology ofthought . The analogy to computers looks to be revealing here: Themore specialized the machine, the more its physical architectureis likely to mirror the structure of its computations; whereas, inthe general purpose machine, form/ function correspondence endsto be less striking , and instantaneous computational structure is



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determi~~1ed by the details of the program being run . At the extremeof this continuum are fully general systems like Turing machines,where fixed architecture is, to all intents and purposes, nonexistent.If , as philosophers speculated for a while , the optimal model ofthe brain were as a realized Turing machine, one would , of course,expect there to be no serious science of neuropsychology. Thepresent point is that any account of central processes as Quineianand isotropic also tends in that direction .

There are, however, much deeper grounds for gloom. The factis that- considerations of their neural realization to one side-global systems are per se bad domains for computational models,at least of the sorts that cognitive scientists are accustomed to em-ploy . The condition for successful science (in physics, by the way,as well as psychology) is that nature should have joints to carveit at: relatively simple subsystems which can be artificially isolatedand which behave, in isolation, in something like the way thatthey behave in situ. Modules satisfy this condition ; Quineianjiso -tropic-wholistic -systems by definition do not. If, as I have supposedthe central cognitive processes are nonmodular , that is very badnews for cognitive science.

Localness to put it the other way around, is a leading characteristicof the sorts of computations that we know how to think about.Consider, once again, the situation in the philosophy of sciencewhere we can see he issues about fixation of belief writ large. Herean interesting contrast is between deductive logic- the history ofwhich is, surely, one of the great success tories of human inquiry -and confirmation theory which , by fairly general consensus is afield that mostly does not exist. My point is that this asymmetry,too, is likely no accident. Deductive logic is the theory of validity ,and validity is a local property of sentences Roughly, the idea isthat the validity of a sentence is determined given a specificationof its logical form, and the logical form of a sentence s determinedgiven a specification of its vocabulary and syntax. In this respect,the validity of a sentence contrasts starkly with its level of confir -mation, since the latter, as we have seen} is highly sensitive toglobal properties of belief systems.44 t is not surprising that phi -losophers discussing confirmation often resort to metaphors of in -teracting fields of forces; just as Gestalt psychologists did whenthey worried about wholistic effects in cognition . The problem in


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both cases s to get the structure of an entire belief system to bearon indi vid ual occasions of belief fixation . We have, to put it b un tl yno computational formalisms that show us how to do this, and wehave no idea how such formalisms might be developed.

I am suggesting hat the reason why there is no serious psychologyof central cognitive processes s the same as the reason why thereis no serious philosophy of scientific confirmation . Both exemplifythe significance of global factors n the fixation of belief, and nobodybegins to understand how such factors have their effects. In thisrespect, cognitive science hasn't even started; we are literally nofarther advanced than we were in the darkest days of behaviorism(though we are, no doubt, in some beneficent respects more dis-illusioned ). If someone- a Dreyfus, for example- were to ask uswhy we should even suppose hat the digital computer is a plausiblemechanism for the simulation of global cognitive processes theanswering silence would be deafening.

The moral, I suppose, is that it would be rational to pray thatGall was at least a little right ; that there are at least some cognitivesystems that are sufficiently modular - hence sufficiently local in

their computational character- that they can be studied prior tothe development of theories of the effects of global determinantsin belief fixation . That our cognitive science has got anywhere atall suggests that this prayer may have been answered. Modifiedrapture


Notes

1 . It may be worth while , before we leave this topic , to point out that Chomsky ' s

talk of mental organs somewhat unilluminates the history of doctrinal relations

b et we en or th od ox C ar tes iani sm an d f ac ul ty ps yc ho log is ts . Re al ( a s o pp os ed t o

N e o - ) Ca rt esi an s we re q ui te of ten opp on en ts of f ac ul ty t he or izi ng , w hi ch t hey

held ( perhaps correctly ) to be incompatible with a due acknowledgment of the

metaphysical unity of the soul . One might , therefore , be surprised to find faculty

psychology endorsed by avowed followers in the Cartesian footsteps . However ,

as we have seen , what the Neocartesians mean by a mental organ - viz . , a body

o f i nna te pr opo si tio na l at tit ude s - i s no t wh at r ea l Ca rte si ans m ea nt b y ( an d de -

nounced as ) mental faculties - viz . , functionally individuated psychological

mechani sms . You need to bea r thi s d is tinc tion in mind i f you wan t a c lear v iew

of how cur rent d ri ft s o f theory rel at e to the ir t radi tional sources . Can ' t s ee the

game without a program .


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The Modularity of Mind.Jerry A. Fodor. 1983 The MIT Press.

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(ebook)(philosophy of mind) jerry a. fodor - modularity of mind-chap5

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