This essay examines Locke’s chapter “Of Identity and Diversity” (Essay 2.27) in the context of the series of chapters on ideas of relations (Essay 2.25–28) that precede and follow it. I begin by introducing Locke’s account of how we acquire ideas of relations. Next, I consider Locke’s general approach to individuation and identity over time before I show how he applies his general account of identity over time to persons and personal identity. I draw attention to Locke’s claim that “person” is a forensic term and analyse his arguments for why the sameness of a human being and the sameness of a substance or soul are neither necessary nor sufficient for personal identity. Instead, Locke argues that personal identity consists in sameness of consciousness. Locke regards persons as moral agents who are accountable for their actions. If a person now is held accountable for a past action it is important that the person now is the same person as the person who did the action. This means that moral accountability presupposes personal identity. Additionally, it will be important to consider whether the person deserves reward or punishment for the action. Locke’s account of moral relations, which he develops in Essay 2.28, addresses this issue and I show how it supplements his account of persons and personal identity.