 The temporal-parts ontology implies that each of us shares our current thoughts with countless beings that diverge from one another in the past or future. If this were true, which of these things should we be? Of course, we are the things we refer to when we say ‘I’, or more generally the referents of our personal pronouns and proper names. But these words would be unlikely to succeed in referring to just one sort of thing—to only one of the many candidates on each occasion of utterance. There would probably be some indeterminacy of reference, so that each such utterance referred ambiguously to many different candidates. That would make it indeterminate what things, and even what sort of things, we are. And insofar as the candidates have different histories and different persistence conditions, it would be indeterminate when we came into being and what it takes for us to persist (Sider 2001b).