Functionalism is a theory which states that to be in mental state means to be in functional condition. Functional status is a state that can individualize or identify because of its causal relations, so the mental state is determined by the particular kind of reason, say, the sensory data input (sensory input), and has a specific type of investigation, say, a certain behavior on the output (behavioral output ). Moreover, mental states as causally related to each other. The whole set of causal relations, which enters this mental state, called the "causal role" in this state, or ...