Functionalist Mind-Body Theories
The most popular approach to the mind-body problem has been functionalism. Functionalism is not, strictly speaking, a materialist mind-body theory; it takes mental properties to be functional properties rather than physical or behavioral properties. Functionalism appears to combine the attractive features of reductive physicalism and logical behaviorism while avoiding their separate problems. To believe that it is going to rain would be, on a functionalist characterization, to possess a token of some internal state type that has a certain functional property. Functionalism has been attractive to many because it avoids this putative implausibility of the type identity theory. Functionalism acknowledges that one mental state type may, in different organisms or even at different times in the same organism, be realized by different physical state types. Functionalism, like type identity theory and logical behaviorism, is a reductive theory; it seeks to tell what mental properties are in non-mental terms. David Lewis's version of functionalism is vulnerable to a certain objection.