Posted by: Xhyra Graf | 28 January 2007

Functionalism [standard]

Functionalism is the doctrine that what makes something a thought, desire, pain (or any other type of mental state) depends not on its internal constitution, but solely on its function, or the role it plays, in the cognitive system of which it is a part. More precisely, functionalist theories take the identity of a mental state to be determined by its causal relations to sensory stimulations, other mental states, and behavior.

For (an avowedly simplistic) example, a functionalist theory might characterize pain as a state that tends to be caused by bodily injury, to produce the belief that something is wrong with the body and the desire to be out of that state, to produce anxiety, and, in the absence of any stronger, conflicting desires, to cause wincing or moaning. According to this theory, all and only creatures with internal states that meet these conditions, or play these roles, are capable of being in pain.

So functionalism is compatible with the sort of dualism that takes mental states to cause, and be caused by, physical states.

Still, though functionalism is officially neutral between materialism and dualism, it has been particularly attractive to materialists, since many materialists believe (or argue; see Lewis, 1966) that it is overwhelmingly likely that any states capable of playing the roles in question will be physical states. If so, then functionalism can stand as a materialistic alternative to the Psycho-Physical Identity Thesis, the thesis that each type of mental state is identical with a particular type of neural state.

3.2 Psycho-Functionalist Theories

A second strain of functionalism, psycho-functionalism, derives primarily from reflection upon the goals and methodology of “cognitive” psychological theories. In contrast to the behaviorists’ insistence that the laws of psychology appeal only to behavioral dispositions, cognitive psychologists argue that the best empirical theories of behavior take it to be the result of a complex of mental states and processes, introduced and individuated in terms of the roles they play in producing the behavior to be explained. For example (Fodor’s, in his 1968, Ch. 3), a psychologist may begin to construct a theory of memory by postulating the existence of “memory trace” decay, a process whose occurrence or absence is responsible for effects such as memory loss and retention, and which is affected by stress or emotion in certain distinctive ways.

On a theory of this sort, what makes some neural process an instance of memory trace decay is a matter of how it functions, or the role it plays, in a cognitive system; its neural or chemical properties are relevant only insofar as they enable that process to do what trace decay is hypothesized to do. And similarly for all mental states and processes invoked by cognitive psychological theories. Cognitive psychology, that is, is intended by its proponents to be a “higher-level” science like biology: just as, in biology, physically disparate entities can all be hearts as long as they function to circulate blood in a living organism, and physically disparate entities can all be eyes as long as they enable an organism to see, disparate physical structures or processes can be instances of memory trace decay — or more familiar phenomena such as thoughts, sensations, and desires — as long as they play the roles described by the relevant cognitive theory.

Psycho-functionalism, therefore, can be seen as straightforwardly adopting the methodology of cognitive psychology in its characterization of mental states and processes as entities defined by their role in a cognitive psychological theory.

3.3 Analytic Functionalism

Like the logical behaviorism from which it emerged, the goal of analytic functionalism is to provide “topic-neutral” translations, or analyses, of our ordinary mental state terms or concepts. Analytic functionalism, of course, has richer resources than logical behaviorism for such translations, since it permits reference to the causal relations that a mental state has to stimulations, behavior, and other mental states.

4.2 Functionalism and Holism

The difficulty is that the characterization of mental states in (all the versions of) functionalism so far presented is holistic. According to functionalism, mental states are to be characterized in terms of their roles in a psychological theory, but psychological theories, whether common sense or scientific, incorporate information about a large number and variety of mental states. Thus if pain is interdefined with certain highly articulated beliefs and desires, then animals who don’t have internal states that play the roles of our articulated beliefs and desires can’t share our pains, and humans without the capacity to feel pain can’t share certain (or perhaps any) of our beliefs and desires. In addition, differences in the ways people reason, the ways their beliefs are fixed, or the ways their desires affect their beliefs — due either to cultural or individual idiosyncracies — might make it impossible for them to share the same mental states. These are regarded as serious worries for all versions of functionalism (see Stich, 1983, Putnam, 1988).

4.3 Characterizing Experiential States

The key strategy in the most successful treatments of perceptual experiences and bodily sensations (Shoemaker, 1984a Clark, 1993; adumbrated in Sellars, 1956) is to individuate experiences of various general types (color experiences, experiences of sounds, feelings of temperature) in part by appeal to their positions in the “quality spaces” associated with the relevant sense modalities — that is, the (perhaps multidimensional) matrices determined by judgments about the relative similarities and differences among the experiences in question.

 This strategy may seem fatal to analytic functionalism, which restricts itself to the use of a a priori information to distinguish among mental states, since it’s not clear that the information needed to distinguish among experiences such as color perceptions will result from conceptual analysis of our mental state terms or concepts. However, this problem may not be as dire as it seems. For example, if sensations and perceptual experiences are characterized in terms of their places in a “quality space” determined by a person’s pre-theoretical judgments of similarity and dissimilarity (and perhaps also in terms of their tendencies to produce various emotional effects), then these characterizations may qualify as a priori, even though they would have to be elicited by a kind of “Socratic questioning”.

 There has been significant skepticism, however, about whether any functionalist theory — analytic or scientific — can capture what seem to be the intrinsic characters of experiential states such as color perceptions, pains, and other bodily sensations;  these questions will be addressed in section 5.1 below.

5. Objections to Functionalism

The previous sections were by and large devoted to the presentation of the different varieties of functionalism and the evaluation of their relative strengths and weaknesses. There have been many objections to functionalism, however, that apply to all versions of the doctrine. Some of these have already been presented in some detail, in particular, the worry about the holism of standard functional characterizations (discussed in section 4.2), and the worry (discussed in sections 4.4. and 4.5) about whether any functional theory can capture the representational content of intentional states. But there are other important objections to functionalism in general that will be addressed in detail here.

5.1 Functionalism and the Problem of Qualia

Even for those generally sympathetic to functionalism, there is one category of mental states that seems particularly resistant to functional characterization. Functionalist theories of all varieties — whether analytic or empirical, FSIT or functional specification — attempt to characterize mental states exclusively in relational, specifically causal, terms. A common and persistent objection, however, is that no such characterizations can capture the qualitative character, or “qualia”, of experiential states such as perceptions, emotions, and bodily sensations, since they would leave out certain of their essential properties, namely, “what it’s like” (Nagel, 1975) to have them. The next three sections will present the most serious worries about the ability of functionalist theories to give an adequate characterization of these states. (These worries, of course, will extend to intentional states, if, as some philosophers have argued (Searle, 1992, G. Strawson, 1986), “what it’s like” to have them is among their essential properties as well. See also entry on Mental Representation.)

5.1.1 Inverted and Absent Qualia

5.1.2 Functionalism, Zombies, and the “Explanatory Gap”

5.1.3 The Knowledge Argument

5.2 Functionalism and Introspective Belief

Another important question concerns the beliefs that we have about our own “occurrent” (as opposed to dispositional) mental states such as thoughts, sensations, and perceptions. We seem to have immediately available, non-inferential beliefs about these states, and the question is how this is to be explained if mental states are identical with functional properties.

The answer depends on what one takes these introspective beliefs to involve. Broadly speaking, there are two dominant views of the matter (but see Peacocke, 1999, Ch. 5 for further alternatives). One popular account of introspection — the “inner sense” model on which introspection is taken to be a kind of “internal scanning” of the contents of one’s mind (Armstrong, 1968) — has been taken to be unfriendly to functionalism, on the grounds that it’s hard to see how the objects of such scanning could be second-order relational properties of one’s neural states (Goldman, 1993). Some theorists, however, have maintained that functionalism can accommodate the special features of introspective belief on the “inner sense” model, since it would be only one of many domains in which it’s plausible to think that we have immediate, non-inferential knowledge of causal or dispositional properties (Armstrong, 1993; Kobes, 1993; Sterelney, 1993). A full discussion of these questions goes beyond the scope of this entry, but the articles cited above are just three among many helpful pieces in the Open Peer Commentary following Goldman (1993), which provides a good introduction to the debate about this issue.

Another account of introspection, identified most closely with Shoemaker (1996a,b,c,d), is that the immediacy of introspective belief follows from the fact that occurrent mental states and our introspective beliefs about them are functionally interdefined. For example, one satisfies the definition of being in pain only if one is in a state that tends to cause (in creatures with the requisite concepts who are considering the question) the belief that one is in pain, and one believes that one is in pain only if one is in a state that plays the belief role, and is caused directly by the pain itself. On this account of introspection, the immediacy and non-inferential nature of introspective belief is not merely compatible with functionalism, but required by it.

But there is an objection, most recently expressed by George Bealer (1997; see also Hill 1993), that, on this model an introspective belief can only be defined in one of two unsatisfactory ways: either as a belief produced by a (second-order) functional state specified (in part) by its tendency to produce that very type of belief — which would be circular — or as a belief about the first-order realization of the functional state, rather than that state itself. Functionalists have suggested, however (Shoemaker, 2001), that there is a way of understanding the conditions under which beliefs can be caused by, and thus be about, one’s second-order functional states that permits mental states and introspective beliefs about them to be non-circularly defined. A full treatment of this objection involves the more general question of whether second-order properties can have causal efficacy, and is thus beyond the scope of this discussion (see Mental Causation entry). But even if this objection can ultimately be deflected, it suggests that special attention must be paid to the functional characterizations of “self-directed” mental states.

5.3 Functionalism and the Norms of Reason

Yet another objection to functionalism raises the question of whether any “theory” of the mind that invokes beliefs, desires, and other intentional states could ever be, or even approximate, an empirical theory. Whereas even analytic functionalists hold that mental states are implicitly defined in terms of their (causal or probabilistic) roles in producing behavior, these critics take mental states, or at least intentional states, to be implicitly defined in terms of their roles in rationalizing, or making sense of, behavior. This is a different enterprise, they claim, since rationalization, unlike causal explanation, requires showing how an individual’s beliefs, desires, and behavior conform, or at least approximate, to certain a priori norms or ideals of theoretical and practical reasoning — prescriptions about how we should reason, or what, given our beliefs and desires, we ought to do (Davidson, 1970, Dennett, 1978, McDowell, 1985). Thus the defining (“constitutive”) normative or rational relations among intentional states expressed by these principles cannot be expected to correspond to empirical relations among our internal states, sensory stimulations and behavior, since they comprise a kind of explanation that has sources of evidence and standards for correctness that are different from those of empirical theories (Davidson, 1970). One can’t, that is, extract facts from values.

Thus, although attributions of mental states can in some sense explain behavior. by permitting an observer to “interpret” it as making sense, they should not be expected to denote entities that figure in empirical laws. (This is not to say, these theorists stress, that there are no causes, or empirical laws of, behavior. These, however, will be expressible only in the vocabularies of the neurosciences, or other lower-level sciences, and not as relations among beliefs, desires and behavior.)

6. The Future of Functionalism

In the last part of the 20th century, functionalism stood as the dominant theory of mental states. Like behaviorism, functionalism takes mental states out of the realm of the “private” or subjective, and gives them status as entities open to scientific investigation. But, in contrast to behaviorism, functionalism’s characterization of mental states in terms of their roles in the production of behavior grants them the causal efficacy that common sense takes them to have. And in permitting mental states to be multiply realized, functionalism offers an account of mental states that is compatible with materialism, without limiting the class of those with minds to creatures with brains like ours.


 Levin, Janet, “Functionalism”, The Stanford Encyclopedia of Philosophy (Fall 2004 Edition), Edward N. Zalta (ed.), URL =



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