  A major rationale of those who think that imagination is not a safe indication of possibility, even when such possibility is not eliminable a priori, is that we can imagine that a posteriori necessities might be false – for example, that Hesperus might not be identical to Phosphorus. But if Kripke is correct, that is not a real possibility. Another way of putting this point is that there are many epistemic possibilities which are imaginable because they are epistemic possibilities, but which are not real possibilities. Richard Swinburne (1997, New Appendix C), whilst accepting this argument in general, has interesting reasons for thinking that it cannot apply in the mind-body case. He argues that in cases that involve a posteriori necessities, such as those identities that need discovering, it is because we identify those entities only by their ‘stereotypes’ (that is, by their superficial features observable by the layman) that we can be wrong about their essences. In the case of our experience of ourselves this is not true.