 We may usefully state Geach’s thesis using the terminology of absolute and relative equivalence relations. Let us say that an equivalence relation R is absolute if and only if, if x stands in it to y, there cannot be some other equivalence relation S, holding between anything and either x or y, but not holding between x and y. If an equivalence relation is not absolute it is relative. Classical identity is an absolute equivalence relation. Geach’s main contention is that any expression for an absolute equivalence relation in any possible language will have the null class as its extension, and so there can be no expression for classical identity in any possible language. This is the thesis he argues against Quine.