Abstract: For a wide range of concepts, a thinker's understanding of what it is for a thing to fall under the concept plausibly involves knowledge of an identity. It involves knowledge that the thing has to have the same property as is exemplified in instantiation of the concept in some distinguished, basic instance. This chapter addresses the question: can we apply this general model of the role of identity in understanding to the case of subjective, conscious states? In particular, can we explain our understanding of what it is for someone else to be in a particular conscious state in terms of our knowledge of the relation of identity which that state bears to some of our own states?

Keywords: identity, conscious states, Frege, concept, Wittgenstein, privacy, evidence,