Are mental states just behaviour, or are they defined by the functional role they play?
Behaviourism and functionalism as accounts of the mental
Two further responses to the mind-body problem in TASC Unit 2: logical behaviourism, which reduces mental talk to behaviour, and functionalism, which defines mental states by their causal role, with key objections.
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What this dot point is asking
This dot point belongs to Unit 2 of the TASC Philosophy course, the mind/body problem. Behaviourism and functionalism are attempts to say what mental states are without positing Descartes' immaterial substance and without the rigidity of the type identity theory. They locate the mental in patterns rather than in a special kind of stuff.
Logical behaviourism
Behaviourism, in the philosophical form developed by Gilbert Ryle, holds that statements about the mind are really statements about behaviour and dispositions to behave in certain ways. To say someone believes it will rain is to say they are disposed to carry an umbrella, agree that rain is coming, and so on. Ryle attacked what he called the dogma of the ghost in the machine, the dualist picture of an inner private mind directing the body, arguing it rests on a category mistake. There is no hidden inner theatre; the mind is a way of describing how a person behaves and is disposed to behave.
Why behaviourism struggles
Behaviourism faces serious objections. First, it seems to leave out the felt quality of experience: a person could be in agony yet, through great self-control, display no pain behaviour at all, which behaviourism cannot easily accommodate. Second, dispositions to behave cannot be specified without referring to other mental states. Whether you carry an umbrella depends not only on believing it will rain but on wanting to stay dry, so mental terms are defined by other mental terms, and the reduction to pure behaviour breaks down. These problems prepared the way for functionalism.
Functionalism
Functionalism, developed by Hilary Putnam and others, says mental states are functional states: a state counts as pain because of the role it plays, being typically caused by bodily damage, causing the belief that one is hurt and the desire to relieve it, and tending to produce avoidance behaviour. What physically realises that role can vary. This is the great strength of functionalism, since it accommodates multiple realisability: a human brain, a very different animal nervous system, or in principle a machine could all have a state filling the pain role, and so all could be in pain. The mind is likened to software that can run on different hardware.
Objections to functionalism
Functionalism faces challenges centred on conscious experience. The inverted qualia problem asks whether two people could share all the same functional states yet have systematically different colour experiences, your red being like my green, with no functional difference to mark it; if so, function does not fix experience. The absent qualia or China brain worry asks whether a system could fill all the functional roles, perhaps the population of a whole nation passing signals, yet have no conscious experience at all. These suggest that role alone may not capture the felt, qualitative side of mind. For the TASC course, present behaviourism and functionalism as progressively more sophisticated alternatives to dualism, and use the qualia objections to assess whether they fully explain consciousness.