Brain bisection raises the intriguing question about how many minds the split-brain patients have. Thomas Nagel and Derek Parfit, who have brought this question into consideration, come to similar conclusions in response to it. They both argue that the question has no answer, that there simply isn't any countable number of minds that the split-brain patients have. In addition, Parfit argues that the split-brain cases can be adequately described only if we adopt a certain particular view about the metaphysical nature of a person. The goal of this paper is to clarify both of those views and, in particular, to explain why Parfit's preference for one model of personhood does not determine how many persons survive brain bisection.
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