IntroductionThe identity thesis asserts that for every psychological state P there is a neural state N such that P=N. In the hope of rendering IT clear and plausible many identity theorists have compared psycho-neural identity claims to such theoretical identities as temperature is identical with molecular mean kinetic energy. However such a comparison admits a weak and a strong interpretation. According to the weak interpretation, psycho-neural identities are said to be like theoretical identities in the sense that the former are (...) contingent claims just as the latter are presumed to be. Identity theorists have appealed to the contingent status of IT in order to meet prima facie objections of the following sort. We can imagine ourselves undergoing a pain, although we are not undergoing the neural process which the identity theorist claims is identical with the pain. Indeed we can imagine ourselves being in pain and yet not having a brain at all. Hence IT is false. Identity theorists have replied by arguing that this objection merely shows that IT is not a necessary truth, or that psychological and neurological terms do not have the same meaning. (shrink)