Terminology Tuesday: Functionalism
The view that mental states are not defined by their intrinsic qualities but by their relations to other states, particularly causal relations. A functionalist would not thereby define a mental state dualistically as a spiritual event nor materialistically as a brain process but would rather say that a mental state is simply a state that plays a certain functional role in an organism’s life. Mental states are those that are caused by certain inputs from the environment, which in turn cause certain behaviors, and that also enjoy certain relations with other inner states. (The latter type of relation is one factor that distinguishes functionalism from behaviorism.) In theory a functionalist could be a dualist, but in reality most functionalists about the human mind are physicalists who believe that material states satisfy the functional roles. See also dualism.
Evans, C. S. (2002). Pocket Dictionary of Apologetics & Philosophy of Religion (pp. 47–48). Downers Grove, IL: InterVarsity Press.