  Here we arrive at a core thesis of functionalism: states of mind are   “multiply realizable”. The property of being in pain can be realized in a wide variety of physical (and perhaps non-physical) systems. A creature is in pain in virtue of being in a state with the right sort of causal profile, some sort of neurological state, say. But the property of being in pain cannot be identified with this neurological state, because creatures of other kinds can be in pain in virtue of being in vastly different physical conditions. Functionalists often put this point by saying that mental properties are “higher-level” properties, properties possessed by objects by virtue of their possession of appropriate “lower-level” properties, their realizers.