Counterpart Theory and the Necessity of Identity

Abstract

In this chapter I want to examine an argument which seems at first sight to demonstrate that in order to maintain the Quinean position with regard to the point of disagreement between Geach and Quine identified at the end of the last chapter one must follow Quine in rejecting the intelligibility of quantified modal logic. I did in fact once think that the argument achieved this purpose, but Michael Dummett made me see that this was mistaken. I still think the argument is worth thinking about, however — not least because of the illumination that is achieved when its fallaciousness is realized, and so (with some preliminary matter) here it is.