What Is Functionalism? Ned Block
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Introduction: What Is Functionalism? Ned Block T IS DOUBTFUL whether doctrines components. The article by Robert Cum I known as "functionalism" in fields as mins (chapter 12) describes functionalism disparate as anthropology, literary criti in this sense. (See also Fodor, 1965, 1968a, cism, psychology, and philosophy of psy 1968b; Dennett, 1975.) chology have anything in common but the name. Even in philosophy of psychology, Computation-representation func the term is used in a number of distinct tionalism. In this sense of the term, senses. The functionalisms of philosophy "functionalism" applies to an important of psychology are, however, a closely knit special case of functional explanation as group; indeed, they appear to have a defined above, namely, to psychological common origin in the works of Aristotle explanation seen as akin to providing a (see Hartman, 1977, especially chap. 4). computer program for the mind. What Three functionalisms have been enor ever mystery our mental life may initially mously influential in philosophy of mind seem to have is dissolved by functional and psychology: analysis of mental processes to the point where they are seen to be composed of Functional analysis. In this sense of computations as mechanical as the primi the term, functionalism is a type of expla tive operations of a digital computer nation and, derivatively, a research strat processes so stupid that appealing to them egy, the research strategy of looking for in psychological explanations involves no explanations of that type. A functional hint of question-begging. The key notions explanation is one that relies on a decom of functionalism in this sense are represen position of a system into its component tation and computation. Psychological parts; it explains the working of the sys states are seen as systematically represent tem in terms of the capacities of the parts ing the world via a language of thought, and the way the parts are integrated with and psychological processes are seen as one another. For example, we can explain computations involving these representa how a factory can produce refrigerators tions. Functionalism in this sense of the by appealing to the capacities of the vari term is not explored here but is discussed ous assembly lines, their workers and in volume 2, part one, "Mental Represen machines, and the organization of these tation." 172 Ned Block Metaphysical functionalism. The that what binds certain types of things last functionalism, the one that this part is together is a physical property. mainly about, is a theory of the nature of Metaphysical functionalists charac the mind, rather than a theory of psycho~ terize mental states in terms of their causal logical explanation. Metaphysical func roles, particularly, in terms of their causal tionalists are concerned not with how relations to sensory stimulations, behav mental states account for behavior, but ioral outputs, and other mental states. rather with what they are. The function Thus, for example, a metaphysical func alist answer to "What are mental states?" tionalist theory of pain might characterize is simply that mental states are functional pain in part in terms of its tendency to be states. Thus theses of metaphysical func caused by tissue damage, by its tendency tionalism are sometimes described as func to cause the desire to be rid of it, and by tional state identity theses. The main con its tendency to produce action designed to cern of metaphysical functionalism is the separate the damaged part of the body same as that of behaviorism (see part one, from what is thought to cause the damage. "Behaviorism") and physicalism (see part What I have said about metaphysi two, "Reductionism and Physicalism"). cal functionalism so far is rather vague, All three doctrines address themselves to but, as will become clear, disagreements such questions as "What is pain?" -or at among metaphysical functionalists pre least to "What is there in common to all clude easy characterization of the doc pains in virtue of which they are pains?" trine. Before going on to describe meta It is important to note that meta physical functionalism in more detail, I physical functionalism is concerned (in shall briefly sketch some of the connec the first instance) with mental state types, tions among the functionalist doctrines not tokens-with pain, for instance, and just enumerated. One connection is that not with particular pains. (For further ex functionalism in all the senses described planation of this distinction see Boyd, in has something to do with the notion of a troduction to part two; Davidson, chap Turing machine (described in the next ter 5; Fodor, chapter 6.) Most functional section). Metaphysical functionalism of ists are willing to allow that each particu ten identifies mental states with Turing lar pain is a physical state or event, and machine "table states" (also described in indeed that for each type of pain-feeling the next section). Computation-represen.. organism, there is (perhaps) a single type tation functionalism sees psychological of physical state that realizes pain in that explanation as something like providing a type of organism. Where functionalists computer program for the mind. Its aim is differ with physicalists, however, is with to give a functional analysis of mental ca respect to the question of what is common pacities broken down into their compo to all pains in virtue of which they are nent mechanical proces~es. If these me pains. The functionalist says the some chanical processes are algorithmic, as is thing in common is functional, while the sometimes assumed (without much justi physicalist says it is physical (and the be-· fication, in my view) then they will be haviorist says it is behavioral).l Thus, in Turing-computable as well {as the Church one respect, the disagreement between Turing thesis assures US).2 Functional functionalists and physicalists (and be analysis, however, is concerned with the haviorists) is metaphysical without being notion of a Turing machine mainly in that ontological. Functionalists can be physi providing something like a computer pro calists in allowing that all the entities gram for the mind is a special case of func (things, states, events, and so on) that tional analysis. exist are physical entities, denying only Another similarity among the func- Part Three Introduction 173 tionalisms mentioned is their relation to fied by the machine table is described by physical characterizations. The causal the machine table and is a realization of structures with which metaphysical func the abstract automaton specified by the tionalism identifies mental states are real machine table. (This definition actually izable by a vast variety of physical sys characterizes a finite automaton, which is tems. Similarly, the information process just one kind of Turing machine.) ing mechanisms postulated by a particular One very simple version of machine computation-representation functionalist functionalism states that each system that theory could be realized hydraulically, has mental states is described by at least electrically, or even mechanically. Finally, one Turing machine table of a certain functional analysis would normally char specifiable sort; it also states that each acterize a manufacturing process abstract type of mental state of the system is iden ly enough to allow a wide variety of types tical to one of the machine table states of machines (wood or metal, steam-driven specified in the machine table (see Put or electrical), workers (human or robot or nam, chapter 17; Block and Fodor, chap animal), and physical s~tups (a given ter 20). Consider, for example, the Turing number of assembly lines or half as many machine described in the following "Coke dual-purpose assembly lines). A third machine" machine table (compare Nelson, similarity is that each type of functional 1975): ism described legitimates at least one no tion of functional equivalence. For exam 5, ple, for functional analysis, one sense of functional equivalence would be: has ca nickel Emit no output Emit a Coke pacities that contribute in similar ways to input Go to 5, Go to 5, the capacities of a whole. ----- In what follows, I shall try to give the dime Emit a Coke Emit a Coke and reader a clearer picture of metaphysical input Stay in o5J a nickel functionalism. ("Functionalism" will be Go to 51 used to mean metaphysical functionalism in what follows.) One can get a crude picture of the simple Machine Versions of Functionalism version of machine functionalism de Some versions of functionalism are scribed above by considering the claim couched in terms of the notion of a Turing that 5, = dime-desire, and 52 = nickel machine, while others are not. A Turing desire. Of course, no functionalist would machine is specified by two functions: one claim that a Coke machine desires any from inputs and states to outputs, and one thing. Rather, the simple version of ma from inputs and states to states. A Turing chine functionalism described above machine has a finite number of states, in makes an analogous claim with respect to puts, and outputs, and the two functions a much more complex machine table. specify a set of conditionals, one for each Machine versions of functionalism combination of state and input. The con are useful for many purposes, but they do ditionals are of this form: if the machine is not provide the most general character in state 5 and receives input I, it will then ization of functionalism. One can achieve emit output a and go into next state 5'. more generality by characterizing func This set of conditionals is often expressed tionalism as the view that what makes a in the form of a machine table (see below). pain a pain (and, generally, what makes Any system that has a set of inputs, out any mental state the mental state it is) is puts, and states related in the way speci- its having a certain causal role.