 Philosophy of mind in the past half-century has been dominated by the thesis that (many) mental concepts are functional concepts, specifying mental states (or properties or events) in terms of the functional or causal roles they play in response to incoming stimuli, in relation to each other, and in generating goal-directed behavior (see, e.g., Putnam 1967, Fodor 1974, and Shoemaker 1984). Functionalists who are also physicalists maintain that mental states are “functionally realized”, in that their defining roles are implemented, on any given occasion, by lower-level physical processes. As a schematic example, the mental state of being a certain kind of physical pain is a state caused by certain kinds of injury to one’s body, and which causes certain kinds of behaviors in response (certain vocal expressions, treating or getting help for the injury, etc.), and (supposes the physicalist), this functional/causal role is always played by some lower-level physical process. 