sophers such as Ryle and by psychologists such as Clark L. Hull (1884–1952).
This approach to mental vocabulary, which came to be called “analytical behaviourism,” did not meet with great success. It is not hard to think of cases of creatures who might act exactly as though they were in pain, for example, but who actually were not: consider expert actors or brainless human bodies wired to be remotely controlled. Indeed, one thing such examples show is that mental states are simply not so closely tied to behaviour; typically, they issue in behaviour only in combination with other mental states. Thus, beliefs issue in behaviour only in conjunction with desires and attention, which in turn issue in behaviour only in conjunction with beliefs. It is precisely because an actor has different motivations from a normal person that he can behave as though he is in pain without actually being so. And it is because a person believes that he should be stoical that he can be in excruciating pain but not behave as though he is.
It is important to note that the Turing test is a particularly poor behaviourist test; the restriction to teletyped interactions means that one must ignore how the machine would respond in other sorts of ways to other sorts of stimuli. But intelligence arguably requires not only the ability to converse but the ability to integrate the content of language into the rest of one’s psychology—for example, to recognize objects and to engage in practical reasoning, modifying one’s behaviour in the light of changes in one’s beliefs and preferences. Indeed, it is important to distinguish the Turing test from the much more serious and deeper ideas that Turing proposed about the construction of a computer; these ideas involved an account not merely of a system’s behaviour but of how that behaviour might be produced internally. Ironically enough, Turing’s proposals about machines were instances not of behaviourism but of precisely the kind of view of internal processes that behaviourists were eager to avoid.
The fact that mental terms seem to be applied in ensembles led a number of philosophers to think about technical ways of defining an entire set of terms together. Perhaps, they thought, words like belief, desire, thought, and intention could be defined in the way a physicist might simultaneously define mass, force, and energy in terms of each other and in relation to other terms. The American philosopher David Lewis (1941–2001) invoked a technique, called “ramsification” (named for the British philosopher Frank Ramsey [1903–30]), whereby a set of new terms could be defined by reference to their relations to each other and to other old terms already understood. Ramsification was based on an idea that had already been noted by the American philosopher Hilary Putnam with regard to the set of standard states of a computer. Each state in the set is defined in terms of what the machine does when it receives an input; specifically, the machine produces a certain output and passes into another of the states in the same set. The states can then be defined together in terms of the overall patterns produced in this way.
States of computers are not the only things that can be so defined; most any reasonably complex entity that has parts that function in specific ways will do as well. For example, a carburetor in an internal-combustion engine can be defined in terms of how it regulates the flow of gasoline and oxygen into the cylinders where the mixture is ignited, causing the piston to move. Such analogies between mental states and the functional parts of complex machines provided the inspiration for functionalist approaches to understanding mental states, which dominated discussions in the philosophy of mind from the 1960s.
Functionalism seemed an attractive approach for a number of reasons: (1) as just noted, it allows for the definition of many mental terms at once, avoiding the problems created by the piecemeal definitions of analytical behaviourism; (2) it frees reductionism from a chauvinistic commitment to the particular way