Hume's theory of personal identity is developed in response to Locke's account of personal identity. Yet it is striking that Hume does not emphasize Locke's distinction between persons and human beings. It seems even more striking that Hume's account of self in Books 2 and 3 of the Treatise has less scope for distinguishing persons from human beings than his account in Book 1. This is puzzling, because Locke originally introduced the distinction in order to answer questions of moral accountability, and Hume's discussion of self in Book 2 provides the foundation of his moral theory in Book 3. In response to the puzzle, I show that Locke and Hume hold different moral and religious views and these differences are important to explain why their theories of personal identity differ.