Any theory analyzing something in terms of its function; that is, any theory claiming that the best, or only, way of defining something is in terms of what it does or the role it plays in the ongoing course of events.
Functionalism tends to define things in terms of their causes and effects, and, in particular, a functionalist in philosophy of mind defines mental states and properties in terms of their causes and their effects as seen in behavior. Two such states or properties will be the same if they have the same causes and effects.
An objection alleged against such functionalism is that it cannot account for the 'inner' nature of conscious experience, for it seems possible in principle that two people might be subject to the same stimuli and exhibit the same behavior while having different inner experiences; or one of them might have none at all (that is, be a zombie).
N Malcolm, '"Functionalism" in Philosophy of Psychology', Proceedings of the Aristotelian Society (1979-80)
Disciplines: Political Science, Sociology
Theory of relation of parts to social whole.
Society is a system of interrelated institutions and processes, which are to be understood in terms of the function they perform for the system as a whole. These functions are not necessarily intended, and may even be contrary to the expressed intentions of those concerned.
Geoffrey Roberts and Alistair Edwards, A New Dictionary of Political Analysis (London, 1991)