In the Ship of Theseus case, no-one is disputing the facts of the matter, and, for the most part, this is so for the other thought experiments presented here. The issue seems to be one of language - yet language does not seem to be deficient, given that we agree on the facts, and that agreement is reached through language. Perhaps the issue is in our intuitions about what we expect language to be able to do.<p>As is always the case, someone (in this case, Parfit) says 'we have to give up the notion of X', where X in this case is personal identity, but that seems to me to be an over-reaction; instead, all we have to do is to accept that there are corner cases where our intuitions about the universality of language do not work. For the most part, we can talk about personal identity without problems, but in the corners, we have to be more specific.<p>We have lived our lives with ambiguous language, so is it that much of a stretch to accept that that's all there is, that there is no Platonic-ideal, complete-and-sound language no matter how careful we are with definitions and usage?