ABSTRACT
Fission occurs when we start out with just one thing, a, and end up, later on, with two things, b and c, each of which has a claim to being identical with a. This proves problematic because identity is a one-to-one relation: at most one of b and c can be identical with a. Fission cases (such as the Ship of Theseus) crop up in discussions of identity over time generally, but here we will mainly be concerned with a standard fission case (sometimes known as the ‘split-brain case’) that appears in the debate about personal identity.
