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Reduction and Elimination in Philosophy and the Sciences

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The <strong>Elim<strong>in</strong>ation</strong> of Mean<strong>in</strong>g <strong>in</strong> Computational Theories of M<strong>in</strong>d<br />

Paul Schweizer, Ed<strong>in</strong>burgh, Scotl<strong>and</strong>, UK<br />

1. The Computational Paradigm<br />

Accord<strong>in</strong>g to <strong>the</strong> traditional conception of <strong>the</strong> m<strong>in</strong>d, semantical<br />

content is perhaps <strong>the</strong> most important feature dist<strong>in</strong>guish<strong>in</strong>g<br />

mental from non-mental systems. For example, <strong>in</strong><br />

<strong>the</strong> scholastic tradition revived by Brentano (1874), <strong>the</strong><br />

essential feature of mental states is <strong>the</strong>ir ‘aboutness’ or<br />

<strong>in</strong>tr<strong>in</strong>sic representational aspect. And this traditional conception<br />

has been <strong>in</strong>corporated <strong>in</strong>to <strong>the</strong> foundations of contemporary<br />

scientific approaches to <strong>the</strong> m<strong>in</strong>d, <strong>in</strong>sofar as <strong>the</strong><br />

notion of ‘mental representation’ is adopted as a primary<br />

<strong>the</strong>oretical device. For example, <strong>in</strong> classical (e.g. Fodorian)<br />

cognitive science, Brentano’s legacy is preserved <strong>in</strong> <strong>the</strong><br />

view that <strong>the</strong> properly cognitive level is dist<strong>in</strong>guished precisely<br />

by appeal to representational content. There are<br />

many different levels of description <strong>and</strong> explanation <strong>in</strong> <strong>the</strong><br />

natural world, from quarks all <strong>the</strong> way to quasars, <strong>and</strong><br />

accord<strong>in</strong>g to Fodor (1975), it is only when <strong>the</strong> states of a<br />

system are treated as representations that we are deal<strong>in</strong>g<br />

with <strong>the</strong> genu<strong>in</strong>ely cognitive level.<br />

The classical paradigm <strong>in</strong> cognitive science derives<br />

from Tur<strong>in</strong>g’s basic model of computation as rule governed<br />

transformations on a set of syntactical elements, <strong>and</strong> it has<br />

taken perhaps its most literal form of expression <strong>in</strong> terms<br />

of Fodor’s Language of Thought hypo<strong>the</strong>sis (LOT),<br />

where<strong>in</strong> mental processes are explicitly viewed as formal<br />

operations on a l<strong>in</strong>guistically structured system of <strong>in</strong>ternal<br />

symbols. But a fundamental tension is already built <strong>in</strong>to <strong>the</strong><br />

classical picture: a central purpose of <strong>the</strong> symbolic<br />

structures is to carry content, <strong>and</strong> yet, to <strong>the</strong> extent that<br />

<strong>the</strong>y are formal elements of computation, <strong>the</strong>ir alleged<br />

content is completely gratuitous. Computation is<br />

essentially a series of manipulations performed on<br />

un<strong>in</strong>terpreted syntax, <strong>and</strong> formal structure alone is<br />

sufficient for all effective procedures. The specification <strong>and</strong><br />

operation of such procedures makes no reference<br />

whatever to <strong>the</strong> <strong>in</strong>tended mean<strong>in</strong>g of <strong>the</strong> symbols <strong>in</strong>volved.<br />

Indeed, it is precisely this limitation to syntactic form that<br />

has enabled computation to emerge as a ma<strong>the</strong>matically<br />

rigorous discipl<strong>in</strong>e. If syntax alone is not sufficient, <strong>and</strong><br />

additional underst<strong>and</strong><strong>in</strong>g or <strong>in</strong>terpretation is required, <strong>the</strong>n<br />

<strong>the</strong> procedure <strong>in</strong> question is, by def<strong>in</strong>ition, not an effective<br />

one. But <strong>the</strong>n <strong>the</strong> purported content of mental<br />

‘representations’ is rendered superfluous to <strong>the</strong><br />

computations that comprise <strong>the</strong> ‘cognitive’ processes of<br />

cognitive science. The <strong>in</strong>tended <strong>in</strong>terpretation of <strong>in</strong>ternal<br />

syntax makes absolutely no difference to <strong>the</strong> formal<br />

mechanics of m<strong>in</strong>d.<br />

For a number of years now <strong>the</strong>re has been a high<br />

profile struggle between oppos<strong>in</strong>g camps with<strong>in</strong> <strong>the</strong><br />

computational approach to <strong>the</strong> m<strong>in</strong>d. In contrast to <strong>the</strong><br />

classical paradigm derived from Tur<strong>in</strong>g, connectionist<br />

systems are based on networks of large numbers of simple<br />

but highly <strong>in</strong>terconnected units that are bra<strong>in</strong>-like <strong>in</strong><br />

<strong>in</strong>spiration. But accord<strong>in</strong>g to Fodor, <strong>the</strong> bra<strong>in</strong>-like<br />

architecture of connectionist networks tells us noth<strong>in</strong>g<br />

about <strong>the</strong>ir suitability as models of cognitive process<strong>in</strong>g,<br />

s<strong>in</strong>ce it still leaves open <strong>the</strong> question of whe<strong>the</strong>r <strong>the</strong> m<strong>in</strong>d<br />

is such a network at <strong>the</strong> representational level. So a<br />

number of connectionists have taken up <strong>the</strong> challenge <strong>and</strong><br />

seek out ways of project<strong>in</strong>g representational content onto<br />

artificial neural networks. One comparatively recent such<br />

attempt (Churchl<strong>and</strong>, P.M.1998, Laakso, A. <strong>and</strong> G. Cottrell<br />

2000, O’Brien, G. <strong>and</strong> J. Opie 2001) uses cluster analysis<br />

to locate ‘vehicles’ of representational content with<strong>in</strong><br />

artificial neural networks, where such clusters serve as<br />

surrogates for <strong>the</strong> classical notion of <strong>in</strong>ternal syntax.<br />

However, I would contend that such attempts suffer<br />

from exactly <strong>the</strong> same built-<strong>in</strong> tension that afflicts <strong>the</strong> LOT<br />

model; namely, <strong>the</strong> purported content for which <strong>the</strong><br />

clusters serve as vehicles does no work <strong>in</strong> <strong>the</strong> process<strong>in</strong>g<br />

path lead<strong>in</strong>g from <strong>in</strong>puts to outputs. Just as <strong>in</strong> <strong>the</strong><br />

classical case, <strong>the</strong> postulation of content with<strong>in</strong> <strong>the</strong><br />

connectionist framework is gratuitous, because it plays no<br />

role <strong>in</strong> <strong>the</strong> cognitive manipulation of <strong>in</strong>puts to yield <strong>the</strong><br />

salient outputs. Indeed, if content weren’t gratuitous, <strong>the</strong>n<br />

computational versions of cognitive process<strong>in</strong>g would be<br />

lamentably deficient <strong>in</strong> terms of <strong>the</strong>ir specification of <strong>the</strong><br />

<strong>in</strong>puts. These are characterized solely <strong>in</strong> formal or<br />

syntactical terms, <strong>and</strong> content is entirely absent from <strong>the</strong><br />

external stimuli recognized by <strong>the</strong> operations that can be<br />

def<strong>in</strong>ed with<strong>in</strong> <strong>the</strong> model. If representational content were<br />

at all relevant, <strong>the</strong>n cognitive systems would have to<br />

process content itself. But accord<strong>in</strong>g to computational<br />

methods, content is not specified with <strong>the</strong> <strong>in</strong>put, nor does it<br />

play any efficacious role <strong>in</strong> <strong>in</strong>ternal process<strong>in</strong>g. So, from a<br />

perspective that takes computation as <strong>the</strong> <strong>the</strong>oretical<br />

foundation for cognition, it seems quite retrograde to posit<br />

content on top of <strong>the</strong> factors that do <strong>the</strong> actual work.<br />

Surely this is an exemplary occasion for <strong>in</strong>vok<strong>in</strong>g<br />

Ockham’s razor.<br />

2. Searle’s Objection<br />

Of course, John Searle’s (1980) celebrated Ch<strong>in</strong>ese Room<br />

Argument (henceforward CRA) runs <strong>the</strong> dialectic <strong>in</strong> exactly<br />

<strong>the</strong> reverse direction: ra<strong>the</strong>r than tak<strong>in</strong>g <strong>the</strong> formal, syntactic<br />

nature of computation as a reason for eschew<strong>in</strong>g content<br />

<strong>in</strong> a properly naturalistic approach to <strong>the</strong> m<strong>in</strong>d, Searle<br />

<strong>in</strong>stead takes it as a reason for reject<strong>in</strong>g computation as<br />

<strong>the</strong> appropriate <strong>the</strong>ory of <strong>the</strong> mental. So, from <strong>the</strong> perspective<br />

of <strong>the</strong> present discussion, it is <strong>in</strong>structive to explicitly<br />

cast Searle’s argument <strong>in</strong> terms of <strong>the</strong> separability of syntactical<br />

structure from its <strong>in</strong>tended mean<strong>in</strong>g. In what follows<br />

I will abstract away from <strong>the</strong> somewhat picturesque<br />

details of Searle’s orig<strong>in</strong>al version <strong>and</strong> express <strong>the</strong> logical<br />

core of <strong>the</strong> CRA via two premises <strong>and</strong> a conclusion:<br />

(1) semantical content is an essential feature of <strong>the</strong><br />

m<strong>in</strong>d,<br />

(2) syntactical manipulations cannot capture this<br />

content, <strong>the</strong>refore<br />

(3) <strong>the</strong> m<strong>in</strong>d cannot be reduced to a system of syntactical<br />

manipulations.<br />

Preimse (1) is an expression of <strong>the</strong> traditional conception<br />

of <strong>the</strong> m<strong>in</strong>d, <strong>and</strong> is accepted by both Searle <strong>and</strong> by his<br />

opponents <strong>in</strong> orthodox cognitive science <strong>and</strong> AI. Classical<br />

cognitive science <strong>and</strong> AI view <strong>the</strong> m<strong>in</strong>d accord<strong>in</strong>g to <strong>the</strong><br />

model of rule governed symbol manipulation, <strong>and</strong> premise<br />

(1) is embraced <strong>in</strong>sofar as <strong>the</strong> manipulated symbols are<br />

supposed to possess representational content. Searle’s<br />

dispute with cognitive science <strong>and</strong> AI centers on his rejection<br />

of <strong>the</strong> idea that <strong>in</strong>ternal computation can shed any real<br />

light on mental content, which leads to his conclusion (3),<br />

313

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