Abstract

The problem of identity across possible worlds is raised with the following questions: What does it mean to say of something in one possible world that it is identical with something in another possible world? How are we to decide whether an individual in one possible world is identical with an individual in another?1 Because the questions concern meaning and verification, it appears to be the case that they presuppose that there are one or more sentences whose meaning and method of verification are in need of explanation. However, although it has been generally presumed to be easy, it turns out to be very difficult to produce a sentence that enables us to formulate the problem and that is not merely supposed to say, but really does say, of an individual in one world and of an individual in another world that the first individual is identical with the second.