narrow content functionalism and the mind-body problem

Narrow Content Functionalism and the Mind-Body ProblemAuthor(s): Kenneth TaylorSource: Noûs, Vol. 23, No. 3 (Jun., 1989), pp. 355-372Published by: WileyStable URL: http://www.jstor.org/stable/2215488 .

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Narrow Content Functionalism and the Mind-Body Problem*

KENNETH TAYLOR

UNIVERSITY OF MARYLAND, COLLEGE PARK

1. PRELIMINARIES

In this essay, I examine narrow content functionalism. Narrow content functionalism is a view about the interrelations between opaque and narrow taxonomies of beliefs. To taxonomize a collection of belief tokens is to segregate those tokens by type. A narrow taxonomy segregates belief tokens by narrow causal types. Two tokens are narrow causal type-identical if and only if they bear type-identical causal and counterfactual relations to type-identical sensory inputs, further states, and behavioral outputs, where these further states, inputs and outputs are abstractly characterized, but without presupposing any individuals (or natural kinds) except the individual (and kinds generable from the existence of that individual) whose states, inputs, and outputs they are and without attributing to them any semantic properties.' On the other hand, an opaque taxonomy segregates belief tokens into de dicto semantic types. The notion of a de dicto semantic type is developed more fully below. Here I will just say that my distinction between de dicto and de re semantic types is meant to express somewhat more clearly and sharply what is tradi- tionally expressed, somewhat misleadingly, in terms of a distinction between de re and de dicto beliefs (or somewhat less misleading in terms of a distinction between de re and de dicto belief attributions). The central claim of the narrow content functionalist is that the system of de dicto semantic types is supervenient upon the system of narrow causal types. He holds that if belief tokens b and b' are

NOUS 23 (1989) 355-372 ? 1989 by Nou's Publications

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tokens of the same narrow causal type, then necessarily they are tokens of the same de dicto semantic type.2

I shall argue, however, that the system of de dicto semantic types does not supervene upon the system of narrow causal types. My argument turns on intuitions about the beliefs of functional, non- molecular duplicates, one on earth, the other on a place which I call fraternal twin earth. I focus on fraternal twin earth with its functional, but non-molecular duplicates because the original twin earth thought experiment, which is often trotted out in support of the thesis I wish here to defend, is, in fact, quite inconclusive against the claims of the narrow content functionalist. But the feature which renders the original thought experiment inconclusive can be factored out. What results is fraternal twin earth. In response to my thought experiment, the narrow functionalist can weaken his initial claim and argue that some restricted class of de dicto semantic types supervenes on the system of narrow causal types. I show that unless we are willing to accept certain largely discredited views, there are strong reasons to doubt that there is a satisfactory principled way of isolating such a class of de dicto semantic types.

2. THE INITIAL ARGUMENT

I begin with what I call the initial argument in defense of narrow content functionalism. Although the initial argument is valid, few narrow content functionalists are likely to endorse it. For it ignores the subtleties that lead narrow functionalists to refrain from assert- ing strict supervenience. But the argument is worth pausing over, both by way of motivating the narrow functionalist search for an account that does better and by way of setting a standard against which to assess the narrow functionalist's success in that search. I first give the argument without elaboration:

(1) There exist beliefs; some beliefs are psychologically relevant contributing causes of behavior; and psychological explanations of behavior which make reference to beliefs are to be interpreted realistically.

(2) Beliefs are contentful and make psychologically relevant contributions to the causation of behavior in virtue of their contents.3

(3) The explicanda of cognitive psychology are behaviors of fine-grained intentional types.

(4) There exist opaque and transparent taxonomies of beliefs- or, as I put it below, taxonomies which categorize belief tokens



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by de re semantic type and taxonomies which categorize tokens by de dicto semantic type-such that there are tokens t and t' which are of the same transparent or de re semantic type, but of distinct opaque or de dicto semantic types and tokens t and t' which are of the same de dicto type, but of distinct de re types.

(5) b and b' are psychologically equivalent if and only if b and V are tokens of the same de dicto semantic type.4

(6) If b is a potential psychologically relevant contributing cause of behavior, then there is a narrow causal type T such that b is of type T and for all b', b and b' are psychologically equivalent if and only if b' is of type T.

It follows straightforwardly from (5) and (6) that:

(7) Once the narrow causal type of a belief token is fixed, the de dicto semantic type of that token is thereby fixed as well.

To accept (1) is to reject both the eliminative materialist claim that there are no beliefs and the instrumentalist claim that "belief talk" has only instrumental value. (Stich 1983) (Churchland 1981) (Dennett 1978) (1) also says that beliefs are causes of behavior and causes of a particular kind. They are not causes of the same kind as external pushes and shoves, or even of the same kind as internal states, like the deterioration of muscle tissue. What distinguishes beliefs as potential contributing causes of behavior from pushes and shoves and the deterioration of muscle tissue as potential contributing causes of behavior is more fully expressed by (2) above. It is not that some belief or other causes some behavior or other. Particular beliefs, in conjunction with further cognitive states, cause particular behaviors and it is a basic thesis of narrow content functionalism that the differing causal potentials of different beliefs is traceable to differences in content. That is, belief tokens with the same content are psychologically equivalent and belief tokens with distinct content are not psychologically equivalent. I define psychological equivalence as follows. b and b' are psychologically equivalent if and only if, ceteris paribus, they make type-identical contributions to the causation of behavior, just in case, that is, it is necessary, ceteris paribus, that whenever b and b' stand in type identical relations to type-identical inputs and further mental states, behavioral outputs of the same (fine-grained intentional) type result.

To see the force of (3) and the notion of a fine-grained intentional type, consider Lex Luthor. He seeks to do harm to Super- man and engages in behavior designed to bring about Superman's demise. If Luthor succeeds he thereby does harm to Clark Kent as well. Indeed, there is no possible world in which Lex Luthor



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succeeds in bringing about the demise of Superman without bringing about the demise of Clark Kent. So there is a sense in which behavior designed to bring about the demise of Superman is type- identical to behavior designed to bring about the demise of Clark Kent. There is an equally clear sense, however, in which behavior designed to bring about the demise of Superman is type-distinct from behavior designed to bring about the demise of Clark Kent. That is, we can distinguish between fine and coarse-grained intentional characterization of behavior. On a fine-grained intentional characterization, behavior designed to bring about the demise of Superman is type-distinct from behavior designed to bring about the demise of Clark Kent, while on a coarse-grained intentional characterization, such behaviors are behaviors of the same type. Similarly, although it is arguably the case that the drinking behavior of my twin earth counterpart is different in coarse-grained intentional type from mine-since he drinks twater and I drink water- it is also arguably the case that our behaviors are of the same fine- grained intentional type. (3) simply says that what matters for the purposes of psychological explanation are not coarse-grained type similarities and differences, but fine-grained type similarities and differences.

The significance of (4) and (5) can be explained by appeal to the widely held intuition that only if we slice beliefs contents, as it were, thinly enough, do we isolate a system of causes, reference to which figures realistically in psychological explanations of behaviors of fine-grained intentional types. Thus take two belief tokens, held by two different believers, which are such that: (a) a transparent taxonomizer counts the two tokens as tokens of the same de re semantic type-(suppose he counts each as a de re belief of Super- man that he is to be eliminated and (b) the opaque taxonomizer counts the two tokens as tokens of distinct de dicto types-(suppose he counts one as a token of the de dicto belief that Clark Kent is to be eliminated, and the other he counts as a token of the de dicto belief that Superman is to eliminated). Then the de dicto taxonomizer has, and the de re taxonomizer has not, segregated the relevant belief tokens into semantic types in a way which tracks with their roles in causing behaviors of fine-grained intentional types.

Notice that it is consistent with (4) that for a single token b there exist types T and T' such that T is a de re type, T' is a de dicto type, and b is both a token of type T and a token of type T'. Thus (4) expresses the fact that the distinction between belief de re and belief de dicto is not a distinction between two classes of entities but a distinction between ways of segregating a single collection of entities-the totality of belief tokens-into semantic types.



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And (5) says that a necessary and sufficient condition for two belief tokens being psychologically equivalent is that they be of the same de dicto semantic type.

(1)-(5) are essential to narrow content functionalism, but one can accept them while rejecting narrow content functionalism. (6), however, is definitive of narrow content functionalism. It says that once the (narrow) syntax of a mental state is fixed, the causal potential is thereby fixed as well.5 Finally, to see that (7) follows straightforwardly from (5) and (6) assume that b and b' are tokens of the same narrow causal type, then by (6) b and b' are psychologically equivalent. But if b and b' are psychologically equivalent, then by (5), b and b' are of the same de dicto semantic type.6

I argue below that there are belief tokens of the same narrow causal type which are of distinct de dicto semantic types. It follows that either (6) or (7) must be false. That is:

(8) Either beliefs of the same narrow causal type need not be psychologically equivalent or psychologically equivalent belief tokens need not be tokens of the same de dicto semantic type.

But a further central intuition of the narrow content functionalist is:

(9) A taxonomy by narrow causal type is sufficient to type- individuate any (contentful) states which supervene on what's in the head and is sufficient to do so in a way which fully accounts for their psychologically relevant causal potential.

But from (8) and (9), it follows that:

(10) Either the explicanda of psychology are not behaviors of fine-grained intentional types or beliefs of the same de dicto semantic type need not be psychologically equivalent.

Now there may be some explanatory enterprise the explicanda of which are not behaviors of fine-grained intentional types, but no such enterprise bears much resemblance to intentional psychology. So if (8) and (9) are both true, and if the narrow functionalist holds, by way of preserving the initial intuition expressed in (2), that there is some system of semantic types such that if T is such a type and b and b' are tokens of that type, then b and b' are psychologically equivalent, then he must show that there is a system of semantic types, distinct from the system of de re semantic types and from the system of de dicto semantic types, such that two tokens of any such type are psychologically equivalent and such that the system of such types supervenes on the system of narrow causal types. I argue below that there are strong reasons to believe that there is



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no principled way to isolate such a system of semantic types. If I am correct, then narrow content functionalism is unworkable.

3. DE DICTO SEMANTIC TYPES

In this section, I give an account of the distinction between de re and de dicto semantic types which is maximally amenable to the claims of the narrow content functionalist and prejudices none of the issues at stake between us. Not every account is non-prejudicial. Burge (1979, 1982), for example, holds that de dicto beliefs are those which are ascribable using terms which occur in oblique position. He argues that duplicates share de dicto beliefs only if whatever obliquely oc- curring terms can be used to correctly ascribe a belief to the one can also be used to correctly ascribe that belief to the other. Con- sider the english term 'water' and the twin english term 'water'- which we will translate 'twater'. Burge notes that oblique occurrences of the english 'water' can be used to correctly ascribe to earthlings the de dicto belief that some glasses somewhere contain some water, but no oblique occurrence of the english term 'water' can be used to ascribe to twin earthlings such a belief (assuming twin earthlings have no contact with water), and mutatis mutandis for 'twater'. This reasoning is supposed to establish non-supervenience. Thus Burge (Burge 1982):

Adam might believe that some glasses somewhere contain some water (... ) Adam te lacks [this] belief. Yet [this] ascription may be interpreted so as not to admit of ordinary existential generalization on positions in the 'that'-clause, and not be de re in any sense. We can even imagine differences in their de dicto beliefs that correspond to differences in truth value. Adam may believe what he is falsely told when someone mischievously says, 'Water lacks oxygen'. When Adamte hears the same words and believes what he is told, he ac- quires (let us suppose) a true belief: twater does lack oxygen.

(. .) Adam and Adamte have relevant propositional attitudes from whose content ascriptions no application of existential generalization is admissible. None of these contents need be applied by the subjects-de re-to the objects in the external world. That is, the relevant attitudes are purely de dicto attitudes. Yet the attitude contents of Adam and Adamte differ.

A suppressed premiss in the above says that tokens of the same de dicto semantic type cannot differ in truth value. But this premiss is unsupported. In any case, it is a contentious enough issue that it would be wise not to take such a thesis as foundational. So I offer a less restrictive construal of de dicto semantic types according to which tokens of the same de dicto semantic type can differ in truth



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value. In so doing, I construe the notion of a de dicto semantic type in a way which prejudices fewer of the issues at stake.7

On my account, the truth value of a belief token cannot be determined independently of fixing reference to particular individuals and kinds or classes of things and restricting quantification to individuals and kinds within a particular domain. But the de dicto semantic type of a belief token can be fully specified independently of fixing reference to particular objects and kinds or restricting quantification to particular domains of objects and kinds. To clarify, think of the semantic type of a belief token as being determined by the way that token constrains the believer's doxastic alternatives. A doxastic alternative is a way that the world "could be" consistent with what an agent believe-s. (Hintikka 1971) (Barwise and Perry 1983) A doxastic alternative is thus a kind of world-a doxastically possible world, but we needn't pause over the exact nature of such worlds.8 For our current purposes, it is enough to think of doxastic alternatives as abstract structures (whose exact set-theoretic nature we leave unspecified) satisfying constraints of two sorts: descriptive constraints and identifying constraints. As a first approximation, let us say that a descriptive constraint constrains doxastic alternatives to contain individuals and kinds satisfying certain descriptions, without constraining those alternatives to contain particular individuals or even individuals drawn from a restricted domain of individuals or kinds. An identifying constraint constrains particular individuals and kinds, or individuals and kinds drawn from a restricted domain of quantification, to occupy a believer's alternatives (and constrains those individuals to have certain properties). With a given belief token there will be associated either determinate descriptive constraints or determinate identifying constraints or both. Two belief tokens are tokens of the same de re semantic type if and only if those tokens have associated with them identical identifying constraints. Two tokens are tokens of the same de dicto semantic type if and only if the two tokens have associated with them identical descriptive constraints.

Assume that Smith believes de dicto that the shortest spy is fat. This comes to Smith's being in a state s with which is associated a descriptive constraint d of the following sort. If A* is a doxastic alternative for Smith, then d constrains A* to contain a shortest spy and that individual is constrained by d to be fat in A *. But there are alternatives A* and B* such that the shortest spy in A* is distinct from the shortest spy in B*. Thus d does not constrain any one individual to be such that in each of Smith's alternatives that individual is the shortest spy. Nor does d constrain the shortest spy to be drawn from a particular domain of individuals. On the



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other hand, Smith's believing de re of the shortest spy that he is fat is Smith's being in a state s with which is associated an identifying constraint d of the following sort. There is a particular x such that x is the shortest spy and if A* is a doxastic alternative for Smith then, x is constrained by d to be fat in A*. So here some particular x is constrained to be such that in each of Smith's alternatives it is fat. But x is not constrained by d to be in each A* the shortest spy.

Consider the belief that the shortest American spy is fat. It constrains the believer's doxastic alternatives to contain a shortest American spy, without constraining any particular individual to be in each alternative the shortest American spy. But an American spy is a spyfrom America. So our specification of the descriptive constraints here must make reference to a particular place. But this is precisely what the notion of a de dicto semantic type is supposed to abstract away from. What we should say is that a token of the de dicto semantic type that a token is of when it constrains a believer's alternatives to contain a shortest spy from America is not of a purely de dicto semantic type. A belief token is of a purely de dicto semantic type if and only if the descriptive constraints it places on the believer's doxastic alternatives can be specified without presupposing any individuals or kinds (other than the individual whose token it is) and without restricting the range of the quantifiers to a particular domain of individuals or kinds.

Truth for a de dicto semantic type consists in the satisfying of the proper descriptive constraints, as I call them, by particular individuals or by particular kinds (or by classes which are not kinds). But what particular individuals or kinds or classes must satisfy the relevant constraints in order for that type to count as true is determined by factors outside of the head of the individual thinker, such as the how the thinker interacts with its surroundings and the nature of its social relation to other thinkers. Further, nothing rules out the possibility that, because of differences in, for example, the sur- rounding environments, two tokens of the same de dicto semantic type can be such that the truth of the one depends on whether, say, H20 satisfies certain constraints, and the truth of the other depends on whether, say, XYZ satisfies certain constraints. This is another way of saying, that descriptive constraints, as such, don't amount to full blown truth conditions. We get full blown truth conditions only when we fix reference and restrict quantification, and this is precisely what descriptive constraints do not fix.9

Now consider Jones and her twin earth counter-part Jones*. (Putnam 1975) Twin earth has been cited in support of the conclusion that the system of de dicto semantic types does not supervene



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on what is in the head. But, in fact, twin earth does not support that conclusion. Indeed, it is a not entirely implausible to think that twin earth shows that the system of de dicto semantic types does supervene on what's in the head. For consider. We can suppose that there is a belief token b of Jones's, a belief token b* of Jones's such that b and b* are tokens of the same narrow causal type, but distinct de re semantic types. Suppose that b is a token of the type that a token is of when it constrains H20 to be such that in each of a believer's alternatives it freezes when it gets cold and that b* is a token of the type that a token is of when it constrains XYZ to be such that in each of the believer's doxastic alternatives it freezes when it gets cold. That there exist such b and b* is unproblematic. But our current b and b* seem also to be tokens of a common de dicto type-the type that a token is of when it constrains each of a believer's doxastic alternatives to contain a potable liquid which freezes when the temperature drops, but does not constrain any one liquid to be in each alternative a potable liquid which freezes when the temperature drops. Now, arguably, identifying constraints attach to belief tokens in virtue of facts about the way the believer is embedded in and interacts with her environment. In particular, we can reasonably maintain that the difference in de re semantic type between b and b* is due to the fact that b is more or less direct- ly causally connected to H20, while b* is similarly connected to XYZ. No such factors are relevant, it may seem, to determining de dicto semantic type. For, arguably, the only possible semantic role for external factors is to fix reference to particular objects or kinds or class of objects and to restrict our quantifiers to objects, kinds and classes in a particular domain. And reference to particular objects and kinds and quantifier restrictions is precisely what the system of de dicto semantic types abstracts away from. If no external factors are relevant to determining de dicto semantic type and if the syntactic theory of mind is a correct account of what is in the head, it may seem to follow that if b and b* are tokens of the same narrow causal type, they are thereby guaranteed to be tokens of the same de dicto semantic type.

4. FRATERNAL TWIN EARTH

But we should not be taken in by appearances. Certainly, twin earth is not sufficient to establish this supervenience claim. Twin earth shows at most that if there exist x, y, b, and b* embedded in relevantly similar environments such that b is a token of x's, b* a token of y's and b and b* are tokens of the same narrow causal type, then b and b* are tokens of the same de dicto semantic type. But the qualifica-



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tion that x and y be embedded in relevantly similar environments is of the essence. Without it, we cannot justifiably infer from the narrow causal type-identity of two tokens to their de dicto semantic type-identity. For there are, I will argue, environments El and E2 such that (1) Jones is embeded in E, and her functional duplicate is embedded in E2 and (2) there is a narrow causal role r such that in E, the state which occupies r in Jones is a token of the de dicto semantic type d and in E2 the state which occupies r in the duplicate is a token of some distinct de dicto semantic type d*.

To demonstrate this possibility, I exploit the multiple realizability of functional roles. Imagine two functional duplicates, one on earth, the other on a place which we shall call fraternal twin earth.'0 In particular, we imagine earth Jones and her fraternal twin Bones, a silicon based life-form who is functionally, though not molecularly, very much like Jones. Like twin earth, fraternal twin earth is in- habited by different natural kinds from the natural kinds that in- habit earth. Now on twin earth there is a liquid, different in kind from H20, but with all the macroscopic properties of H20. It freezes when it gets cold, falls from the sky on cloudy days. On fraternal twin earth, however, there is no such liquid. In fact, there are no liquids at all on fraternal twin earth. There are various substances- which twin earthlings call 'liquids', but which we shall call 'liquids*', to avoid confusion-made up of very fine, but not microscopic, particulate matter." In fact, there are as many varieties of such substances as there are varieties of liquids on earth. There is one substance, with the complex chemical formula ABC, which on fraternal twin earth is called 'water'-which, again to avoid confusion, we will call 'water*'. ABC is, in its various states, as ubiquitous on fraternal twin earth as H20 in its various states is on earth. It plays roughly the role in the life of fraternal twin earthlings that water plays in the life of earthlings. That is, they use it to nourish (silicon-based) plants, to quench thirst, and to cleanse their bodies. But there are important differences between H20 and ABC. For example, H20 freezes when it gets' cold enough. Since ABC isn't a liquid at all, it doesn't freeze when it gets cold. But it does undergo an interesting change. At low temperatures, ABC particles cohere more readily to one another and become less fluid*. A bunch of ABC particles in this state is in the frozen* state. Further, fraternal twin earthlings have a special term for ABC in its frozen* state. They call it 'ice'-again we shall call it 'ice*'. Fraternal twin earthlings believe that ice* is frozen* water*. Further, ABC in its various states affects the sensory receptors of fraternal twin earthlings in just the ways that H20 in its various states affects the sensory recep-



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tors of earthlings. Thus, for example, when a normal fraternal twin earthling touches ABC in its frozen* state certain sensory receptors fire. The firing receptors are thefunctional (not physical) equivalents of the receptors that fire when a normal earthling touches H20 in its frozen state. Finally, imagine that both Jones and her fraternal twin Bones live in societies not very scientifically advanced and that neither they, nor any one in their respective socities, knows anything about molecular structure. Imagine, in particular, that neither Bones nor anyone in her society has any idea that water* is a substance made up of fine particulate matter and that none of them presented with a sample of H20 in its liquid state could easily tell that it was not a liquid*.

Now imagine two molecularly identical cups, one on Jones's desk on earth, the other on Bones's molecularly identical desk on fraternal twin earth; one filled with water, the other filled with water*. Imagine a cold wintry night on earth and a similar night on fraternal twin earth. The water in Jones's cup freezes; the water* in Bones's cup freezes*. Jones perceives the frozen water in the cup. Bones, with functionally equivalent receptors, perceives the frozen* water* in the cup. Jones and Bones come to be in states s and s', respectively, each occupying role r. r is such that (1) if x occupies r on earth and x is caused by the perception of frozen water in a cup then x counts as the belief of the water in the cup that it is frozen and (2) if x occupies r on fraternal twin earth and x is caused by the perception of frozen* water* in a cup then x counts as the belief of the water* in the cup that it is frozen*.

Now Bones's belief of the water* in the cup that it is frozen* and Jones's belief of the water in the cup that it is frozen are clearly tokens of different de re semantic types. For Jones's belief constrains the water in the cup to be frozen in each of her doxastic alternatives, while Bones's belief constrains the water* to be frozen* in each of her doxastic alternatives. But if the narrow content functionalist is right the two belief tokens are tokens of a common de dicto semantic type and we ought to be able to determine exactly which such type just by factoring out all reference to particular individuals and kinds or classes of things and factoring out quantification over restricted domains of individuals and kinds or classes of things. Further, it ought to be the case that any belief token of the narrow causal type r is a token of this same de dicto semantic type.

But notice that even if we factor out the reference to particular cups, to particular desks, to particular natural kinds, and even if we do not restrict our quantifiers, there remain two distinct de dicto semantic types such that Jones's token is a token of the one type



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and Bones's token is a token of the other type. For Jones has a belief which is a token of the de dicto semantic type that a token is of when it constrains the believer's doxastic alternatives to contain, a unique sample of frozen liquid in a cup, and Bones's belief is a token of the de dicto semantic type that a token is of when it constrains the believer's alternatives to contain a unique sample of frozen* liquid* in a cup. Thus Jones's belief token and Bones's belief token evidently place different descriptive constraints on their respective doxastic alternatives. And from this it follows that the two tokens are of distinct de dicto semantic types. Thus we have shown that in spite of the fact that Bones and Jones are in states of the same narrow causal type, those states are of distinct de dicto semantic types.

The foregoing argument shows that the system of de dicto semantic types does not supervene on the system of narrow causal types. Of course, that argument turns on a particular construal of the class of de dicto semantic types, so one might argue that fraternal twin earth shows only the need for some re-working of our treatment of de dicto semantic types. One might reason to this view as follows. First, one notices that de dicto semantic types are introduced to satisfy two distinct explanatory demands. The first demand arises from the need for an explanation of referential opacity. We want to know why, given that Clark Kent and Superman are one and the same individual, we are justified in attributing to Lois Lane the belief that Superman can fly, but not justified in attributing to her the belief that Clark Kent can fly. The answer, of course, is that in attributing to Lois the belief that Superman can fly we subsume her belief token under a different de dicto semantic type than we would were we to attribute to her the belief that Clark Kent can fly. The second explanatory demand arises from the assumption that beliefs are (a) internal causes of behavior which are at least supervenient upon brute bodily and brain states and (b) semantically typable states, such that beliefs of the same semantic type make type-identical contributions to the causation of behavior. The second demand is thus a demand to find a system of semantic types which supervenes on what's in the head and which segregates belief tokens into semantic types in a way which accords with their roles as psychologically relevant contributing causes of behavior. It is ob- vious that the system of de re semantic types does not satisfy this explanatory demand. So it seems reasonable to suppose that the system of de dicto semantics types does.

So the system of de dicto semantic types seems to satisfy both of our explanatory demands. Indeed, one may hold that it is con- stitutive of the system of de dicto semantic types that it does so. But



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our fraternal twin earth thought experiment shows that the system of de dicto semantic types, as currently understood, does not meet both demands. So one may want to conclude that my argument is therefore a reductio ad absurdum of our understanding of the distinction between de re and de dicto semantic types. Another way to put this point is to say that the our understanding of the distinction between de re and de dicto semantic types assimilates de dicto semantic types to de re semantic types far more closely than is desirable- too close, in fact, to enable the system of de dicto semantic types to do the explanatory work for which they are intended.'2

However, my argument counts as a reductio only if one can make stick, on independent grounds, the claim that it is definitive of the notion of a system of de dicto semantic types that it simultaneously satisfies our two explanatory demands. Otherwise, my argument is not a reduction but a refutation of the claim that the system of de dicto semantic types must simultaneously satisfy these two explanatory demands. Further, it should be clear that I have given a construal of the system of de dicto semantic types which is minimal- ly prejudicial to the issues at stake between myself and the narrow content functionalist. So it is hard to see how an alternative construal is likely to help the case of the narrow content functionalist. Perhaps a prima facie reasonable strategy is for the narrow content functionalist to insist that fraternal twin earth illustrates only the need to slice semantic types more thinly than we have so far done.'3 He may argue, for example, that only some of the de dicto semantic types generated by our approach can be narrowly individuated and that there is a principled distinction between those which can be so individuated and those which cannot. He may appeal, for example, to what we might call purely qualitative concepts and claim that only those de dicto semantic types can be narrowly individuated which involve only purely qualitative concepts. A purely qualitative concept is one the content of which can be specified without reference to particular individuals or particular kinds or classes of things and without quantifying over restricted domains of individuals and kinds or classes of things. Call a concept not of this sort a wide concept. Arguably, only those de dicto semantic types which involve no wide concepts should count as purely de dicto semantic types in the sense outlined earlier on. And now the narrow functionalist may want to claim that only the system of purely de dicto semantic types supervenes on what's in the head. The concept of freezing is wide. For freezing is a kind of change that liquids as opposed to liquids* undergo. And it just may be that what makes a mental state a token of a semantic type which involves the concept freezing, as opposed the concept freezing*, is that state's being related, causally or other-



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wise, to liquids, as opposed to liquids*. If so, it will be no embar- rassment to the narrow functionalist that two states which occupy the same narrow causal role turn out to be such that one is of a de dicto semantic type involving the concept freezing and the other is of a de dicto semantic type involving the concept freezing*. For such semantic types are not pure de dicto semantic types.

For the moment, and just as a heuristic device, construe concepts as concrete, but semantically typable, mental states such that: (1) they have two states, an on state and an off state, and (2) to specify the content of a concept is to specify when its on state ought to be tokened.14 The narrow content functionalist must show that the concepts involved in pure de dicto semantic types are narrowly individuable. If a concept is narrowly individuable, its content does not depend on how correct tokenings of the on/off states of the concept are correlated with features of the external environment. Its content will depend only on its role in a solipsistically characterized system of states. This system does include input states. So perhaps we can semantically type the concept hard-a paradigm example of a qualitative concept-by specifying the links between its on/off states and various input states. One might think, for example, that the concept hard is that concept the on state of which ought to be tokened just when an input state of kind h obtains, for some appropriate h. But the deep problem is to characterize h solipsistically. One might want to posit hard qualia. One might go adverbial and posit episode of sensing hardly. And one might then attempt to narrowly individuate the relevant episodes or qualia. But there's a clear danger of vicious circularity here. One cannot, without vicious circularity, maintain that hard qualia are the ones, occurrences of which justify tokenings of the on state of the concept hard. If one is not committed to narrow individuation, one might try to isolate the relevant qualia or episodes by indirectly correlating them with ostensively picked out features of the environment. One might say, for example, "Episodes of sensing hardly are those sensory episodes which are correlated with the presence of objects like this [pounding some hard object]" But clearly the narrow content functionalist can't make such a move.

I do not need to deny here the existence of narrowly individuable qualitative states. I can allow that tingling sensations and dull pains are narrowly individuable. And perhaps to believe that one is having a dull pain is just to be in a state occupying a certain narrow causal role. But there is an important difference between the belief that one is having a dull pain and the belief that there is a red object present. The former, but not the latter, purports to represent only what is happening in the inside of the agent, while the latter, but



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not the former, purports to represent what is happening outside of the agent. One might insist that to believe that a red object is present is just to represent oneself as being causally related to an object which is stimulating one's receptors in a certain narrowly specifiable way. But this line implies that our qualitative concepts are, in the first instance, representations of what's happening inside, and only derivatively representations of what's happening outside. This view is, I think, deeply misguided. It is true enough that happenings at our receptive surfaces causally mediate between happenings in the world and tokenings of our concepts-and this is so for both qualitative and non-qualitative concepts. But it does not follow that those concepts in any sense represent or are of or about those internal happenings. Now I won't try to argue here that even qualitative concepts represent, in the first instance, things in the external world rather than mediating internal happenings. I will just say that the denial of such a view looks to me like a return to the bad old sense datum days or to the bad old Cartesian days, when it was thought that, in the first instance, the mind was essentially self- regarding and unable (except, perhaps, via the good graces of a non-deceiving god) to represent things in the external world.

In any case, it is clear that it is the representational features of our qualitative concepts, and not merely their causal connections to internal mediating occurrences, which are relevant to functionalism. So what the narrow functionalist must show is that the (psychologically relevant) representational features of our qualitative concepts are somehow fully determined by the causal connections between the tokenings of such concepts and internal mediating occurrences. The difficulty is that it's very difficult, to say the least, to see how to do this without lapsing into a view which makes that which is represented by our qualitative concepts, which alone, according to our functionalist, figure in pure de dicto semantic types, something "in the head." Now it is clear, I think, that along this path lies a return to something like a sense datum theory. I will not rehearse familiar reasons for rejecting such views. For the burden of proof rests squarely on the shoulders of anyone who wants to return to those bad old days and equally clear that the burden has not been discharged.15

Now I think that I have conclusively shown that de dicto semantic types do not supervene on what's in the head-not even plus or minus a bit. Further, I have shown that there are strong reasons to doubt that there is any more thinly sliced system of pure de dicto semantic types which does supervene on what's in the head. Though I do not claim that in establishing these results I have conclusively refuted narrow content functionalism, I do claim that I have shown



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that there remains a rather stiff challenge to that view. In particular, the narrow content functionalist must show that there exists a system of supervening semantic types, more thinly sliced than the system of de dicto semantic types, and he must do so while avoiding what seems an almost inevitable lapse into something like phenomenalism or a crude sense datum theory. If he cannot avoid this lapse, then he must offer us some fresh reasoning which makes that approach far less problematic than it has come to seem. This is, I think, a daunting challenge, and one that is unlikely to be met for some time to come.

REFERENCES

Lynne Rudder Baker 1985 What do We Have in Mind, Midwest Studies in Philosophy, vol. 10.

Jon Barwise and John Perry 1983 Situations and Attitudes, Cambridge Massachusetts; MIT Press/Bradford Book. Tyler Burge 1979 Individualism and the Mental, Midwest Studies in Philosophy, vol. 4. French, Uehling,

and Wettstein (eds).

1982 Other Bodies, in Thought and Object, Oxford: Oxford University Press, Andrew Wood- field (ed).

Roderick Chisholm, 1957 Perceiving; A Philosophical Study. Ithaca: Cornell University Press.

Paul Churchland 1981 Eliminative Materialism and the Propositional Attitudes, The Journal of Philosophy,

78, 67-90.

Daniel Dennett 1978 Intentional Systems, in Brainstroms, Montgomery, Vermont: Bradford Books. Fred Dretske, 1981 Knowledge and the Flow of Information, Cambridge, Massachusetts: MIT Press/Bradford

Books.

Jerry Fodor 1980 Methodological Solipsism Considered as a Research Strategy in Cognitive Psychology,

The Behavioral and Brain Sciences, 3, 63-73, reprinted in Representations, Cambridge, Massachusetts: The MIT Press/Bradford Books.

1982 Cognitive Science and the Twin Earth Problem, Notre Dame Journal of Formal Logic 23, 98-118.

1987 Psychosemantics, Cambridge, MA: MIT/Bradford Books. Jaakko Hintikka 1971 Semantics for Propositional Attitudes, in Reference and Modality, Leonard Linsky,

ed., Oxford: Oxford University Press.

1975 Impossible Possible Worlds Vindicated, Journal of Philosophical Logic, 4, 475-84.

Frank Jackson 1977 Perception: A Representative Theory, Cambridge England: Cambridge University Press.

Leonard Linsky 1984 Oblique Contexts, Chicago: University of Chicago Press.

Hilary Putnam 1975 The Meaning of 'Meaning', in Philosophical Papers, Vol 2, Cambridge, England:

Cambridge University Press.

Stephen Stich, From Folk Psychology to Cognitive Science: The Case Against Belief, Cambridge,



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Massachusetts: MIT Press/Bradford Books.

Kenneth Taylor forthcomingSupervenience and Levels of Meaning Southern Journal of Philosophy.

Stephen White 1 982 Partial Character and the Language of Thought, Pacific Philosophical Quarterly 63,

347-365.

NOTES

*This paper is a revised version of a paper that was completed during the 1985-86 academic year while I was on leave from Wesleyan University and affiliated as a postdoctoral fellow with the University of North Carolina at Chapel Hill. I am grateful to the department there for the generous hospitality afforded me during that year. I am especially grateful to Kate Elgin, Bill Lycan, Stan Munsat, Mike Resnick, Jay Rosenberg, and Geoffrey Sayre McCord for comments on earlier drafts. Versions of this paper were presented to UNC- Chapel Hill Philosophy Department and to the Five Colleges Propositional Attitudes Task Force. My debts to the members of the Task Force-Lee Bowie, John Connolly, Jay Garfield Murray Kiteley, Meredith Michaels, and Tom Tymoczko-are also considerable. A shortened version of this paper was also presented at the 1987 meeting of the Central Division of the APA. A lively discussion ensued for which I am most grateful. Finally, I express appreciation to Hector-Neri Castafieda and to two anonymous referees for this journal, for helpful and insightful comments on earlier drafts.

1It is worth pausing over the fact that narrow causal type-identity is defined by reference to abstractly characterized input, internal states, and behavioral outputs, and not by reference to states, input, and output, characterized in brute physical terms. This is important because it allows, among other things, for the multiple realizability of systems of narrow causal types. I stress this fact because of an issue raised, in correspondence, by Castafieda. Castafieda has suggested to me that we need some quantifiers on the right-hand side of the bicondi- tional, and has suggested that it's hard to find any quantifiers that are satisfactory. For example, if we put "some" on the right-hand side, it then reads ". . . they bear type-identical causal and counterfactual relations to some type-identical sensory states. . ." Clearly this is too permissive a criterion. But replacing "some" with "all" would yield too restrictive a criterion. In particular, it would make it hard to see how two organisms which were radically different at the brute physical level could possibly realize the same system of narrow causal types, since, persumably, the physical states of two such organisms might well bear radically different causal and counterfactual relations to physically similar inputs. I think the way around this difficulty is indeed to replace "some" with "all", but to interpret "all" as ranging not over brute physical inputs, interenal states, and outputs but over abstractly, but still non-semantically, characterized states. For such abstract, non-semantic characterizations of mental states the narrow functionalist typically appeals to the mental sentence story, according to which beliefs, and propositional attitudes generally, are relations to mental sentences couched in some canonical idiom. As such, the narrow content functionalist is committed to at least the following theses: (1) To be the bearer of a propositional attitude, A TT S, is to stand in a certain (computational) relation R to a mental sentence token T, where T is a formula of some canonical idiom; (2) The way in which A TT S causally and counter- factually interacts with input, other mental states, and output is to be explained first by appeal to the sort of role that states of the same broad category play in the overall psychological dynamics of the agent and more particularly by appeal to the abstract syntactic properties of the particular token T to which the subject of A TT S bears R.

2A caveat is in order. Even the staunchest defenders of narrow content functionalism willl not claim that the system of de dicto semantic types is strictly supervenient on the system of narrow types. See, for example, Fodor (1980). For a helpful discussion of some of the difficulties in settling upon the exact thesis involved in narrow content functionalism see Stich (1983).

3Some will object that beliefs cannot be causes, because they are not occurrences. If you have this difficulty interpret talk of beliefs as causes as meaning that beliefs, type- individuated by content, figure in law-like psychological generalizations, explanatory of behavior.



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4This premiss is not meant as a definition of psychological equivalence. For a definition see below.

5A referee for this journal has pointed out that there may be some elements of syntax-for example, individuation of lexical items-which depend on semantical considerations. Of course, the narrow causal types of the narrow functionalist must not appeal to anything but narrow syntax.

6Now given that narrow causal role of a token is supposed to be specifiable without reference to any facts about the semantic type of that token, the further claim that the de dicto semantic type of a belief token is also fully determined once its narrow causal type is determined may seem paradoxical. But the air of paradox dissipates if one keeps in mind that the narrow content functionalist is making not an analytic claim about the meanings of belief ascriptions, but a supervenience claim. Then assuming that facts about narrow causal type in turn supervene on the brute physical facts, the narrow content functionalism can be seen as putting forth a rigorously physicalistic, though non-reductionist hypothesis con- cerning what we must fix, if we are to fix the de dicto semantic type of a belief token.

7Indeed, once we have this notion of de dicto semantic type in hand, it will, I think, be clear that the sort of arguments offered in (Burge 1979 and 1982) do nothing to refute the claims of the narrow content functionalists.

8At least some doxastic possibilities are metaphysically impossible. Suppose that Jones believes that Hesperus is not Phosphorous. Then in each ofJones's alternatives the-Hesperus- object, as we might call it, and the-Phosphorous-object are going to distinct. But well-known arguments show that there are no metaphysically possible words in which Hesperus and Phosphorous are distinct. It follows that the set of doxastic alternatives of an agent is not a subset of the set of all metaphysically possible worlds. (Hintikka 1975) (Linsky 1984) If my view is correct, it follows that the role which proper names play within doxastic and epistemic contexts is radically different from the role they play in transparent and alethic model contexts. Kripke and others have made a strong case that proper names are rigid designators, but I think this claim holds good only for names which occur in transparent and alethic modal contexts. In doxastic and epistemic contexts, they function entirely dif- ferently as what might be called flaccid designators. We can say, that is, that proper names are metaphysically rigid, but epistemically flaccid designators.

9If we adopt my approach to de dicto semantic types, then Burge, in the passage quoted above, seems simply to smuggle in an illicit reference to particular objects and kinds and an illicit restriction on the range of the quantifiers. Now it may well be true that our common sense attributions of de dicto beliefs already come with the reference of at least some terms fixed and with certain built-in quantifier restrictions. In that case, much of Burge's work shows that our common sense opaque taxonomy of beliefs is not a taxonomy which segregates belief tokens into pure de dicto semantic types. But no one, as far as I know, has ever claimed the contrary. My problem with Burge's work, then, is that it shoots at the wrong target and that, consequently, it is open to the narrow functionalist to dismiss Burge's reasoning as entirely irrelevant to the issue at hand.

?Fraternal twins earth is inspired by an example from (White 1982, Baker 1985). "I add the clause "not microscopic" to forestall the claim that liquids too are made

up of fine particulate matter. The particles which I have in mind are not molecular particles. They're more like extremely fine grains of sand,

"2Here, and throughout these last two paragraphs, I am indebted to insightful observa- tions by Hector-Neri Casafieda.

"3There is an alternative strategy, what I elsewhere call the multi-level strategy. This strategy posits various levels of semanticity and argues that at a sufficiently high level we find semantic properties which supervene on brute states of the brain. This strategy is ex- emplified in Stephen White (1982) and more recently in Fodor (1987). For an attack on the multi-level approach see Taylor (forthcoming).

"4Evidently, this is more plausible for perceptual concepts, but the difficulties for the narrow content functionalist multiply when we consider non-perceptual concepts.

"5For a superb recent discussion of whether the object of perception is inside of the perceiver or outside of the perceiver see the sixth chapter of Dretske (1981). For a superb early discussion of this same issue see Chisholm (1957). For a recent, and very tightly argued defense of sense datum theory see Frank Jackson, (1977).



narrow content functionalism and the mind-body problem

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