Abstract
In recent years, functionalism has emerged as the most appealing candidate for a materialistic theory of mind. Its central thesis - that types of mental states can be defined in terms of their causal and counterfactual relations to the sensory stimulations, other internal states, and behavior of the entities that have them - offers hope for a reasonable materialism: it promises type-identity conditions for beliefs, sensations, and emotions that are not irreducibly mental, yet would permit entities that are physically quite different to be in mental states of the same type.