Polger on the Illusion of Contingent Identity

Abstract

Thomas Polger has argued in favour of the mind–brain type‐identity theory, the view that mental states or processes are type‐identical to states of the central nervous system. Acknowledging that the type‐materialist must respond to Kripke’s modal anti‐materialist argument, Polger insists that Kripke’s argument rests on dubious assumptions concerning the identity conditions of brain states. In brief, Polger claims that one knows that x and y are non‐identical when one knows the identity conditions for both x and y. Replace x and y with ‘brain states’ and ‘sensations’ and it follows that one can know that brain states and sensations are non‐identical only if one knows the identity conditions for brain states. But according to Polger, we do not know the identity conditions for brain states. Hence, we should not be so confident that brain states and sensations are non‐identical after all. But Polger’s account is terribly flawed. Ironically, if Polger’s scepticism is warranted, then Polger himself has no good reasons to be a type‐materialist. But more importantly, Polger’s scepticism regarding the identity conditions of brain states is deeply defective. We do, I submit, understand the identity conditions of brain states. In the end, I submit, Kripke is safe from Polger.