H. P. Grice on relative personal identity

In the case of, for example, the truncated cup we saw that one option is to claim that Cup is earlier distinct from Tcup [cup minus its handle], but later identical with Tcup. According to this option the identity of Cup with Tcup is only temporary. We also saw that many refuse to countenance temporary identity because it allegedly conflicts with Leibniz's Law [LL]. After all, later Cup, but not Tcup, apparently later has the property of having had a handle.

Despite this putative conflict with LL, some philosophers are prepared to defend temporary identity as the best solution to the puzzles about diachronic identity. George Myro does so by restricting the scope of LL to exclude such properties as having had a handle (Myro 1985). Gallois (1998) does so by arguing that if the identity of Cup and Tcup is temporary, we cannot infer from Tcup having had a handle earlier that earlier Tcup has a handle.