On the Necessity of Personal Identity

This chapter defends the claim that every good answer to the following question implies being numerically identical with: The Why Question: What way of being related to a (conscious) person at a future time explains why that person will have (at that time) what matters in survival for you? So this chapter defends the claim that personal identity is necessary for what matters in survival. This chapter also shows that Derek Parfit’s famous argument to the contrary fails. But there is no single way in which Parfit’s argument uncontroversially goes wrong. Rather, the way in which that argument fails depends on this or that controversial metaphysics of persistence. So that argument fails in one way given endurance, and it fails in a different way given (for example) stage theory. Most importantly, there is no metaphysics of persistence on which that argument succeeds.