| The problem of personal identity is a specific instance of the more general metaphysical puzzle of explaining how a single entity persists over time. In this dissertation, I argue against a certain popular approach to this problem: the so-called psychological criterion, according to which the persistence over time of a person consists in some sort of psychological continuity over time. Advocates of the psychological criterion typically support their view by appealing to various thought experiments designed to show that psychological continuity can come apart from the continued existence of whatever substantial entity we might take to be the ordinary subject of psychological continuity: a human body or living organism, on one view, a soul or immaterial substance, on another view. The conclusion we are supposed to draw from these thought experiments is that the person herself can survive without the same body or soul, and so cannot be identical with body or soul. Despite its popularity, however, I argue that the strategy of appealing to such thought experiments simply begs the question against the alternative views. I then argue that advocates of the psychological criterion do not have the resources to develop a non-question-begging argument for their view. The psychological criterion does not yield a coherent account of the metaphysical nature of persons, and so arguments for the psychological criterion fail in principle. The kind of account we need is one that explains personal identity in terms of some substantial entity with determinate identity conditions: something that can survive breaks in psychological continuity because it is the subject of psychological life, the thing that underlies and causes both the continuities and the discontinuities. The most plausible such account, I claim, is the biological criterion, according to which personal identity over time is to be defined, not in any psychological terms, but in terms of the continued existence over time of a particular living animal: specifically, a particular human being. |
