Functionalism, Causation, and Causal Relevance

This paper argues that functional states, and states defined in terms of them, cannot be causally relevant to the output or state transitions in terms of which those functional states are defined, or to intervening mechanisms or to anything to which their output is in turn causally relevant. Functional states therefore cannot be correctly invoked in what I call "simple causal explanations". Explanations which cite functional states are instead a species of explanation by appeal to dispositional properties. Functionalists about the mental are therefore committed either to denying that ordinary explanations of behavior by appeal to mental states are simple causal explanations or to denying that they are true. Special difficulties for functionalism arise in the case of conscious mental states.