Personal Identity

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The issue of personal identity concerns the issue of what constitutes the continued existence of a person over time. Or, to put it another way, in personal identity we seek to provide answers to questions such as 'What makes a person A at time t1 the self-same person as a person B at a later time t2?'.One of the most important contemporary theories of personal identity is known as the psychological criterion. According to the psychological criterion a person's continued existence is constituted by 'psychological continuity'. In other words, B at t2 is the self-same person as A at t1 if enough of B's psychological states are causally related to A's psychological states in the right sort of way.In recent years the psychological criterion has been subject to vigorous attack. Much recent work in personal identity has questioned the adequacy of the psychological criterion's account of the relation between the person you are and human being you also are. The standard version of psychological criterion distinguishes between these two things and takes them to be distinct. They do this because of various thought experiments, such as John Locke's story of the minds of a prince and a cobbler swapping places. The conclusion that modern Lockeans draw from this story is that if it is logically possible that this could happen (even if it is not technically possible), then a person and their body cannot be the same thing. But this raises the question of what is the person, if it is not the same thing as the body or the brain, and if it is not conceived of as a traditional non-physical soul.Most psychological theorists wish to maintain that the person is a physical object of some sort, but as they are committed to the view that the person and body are distinct, they are committed to the apparently counter-intuitive view that two distinct physical objects exist, the person and the body. But how is it that there only appears to be one physical object associated with our existence? Their solution to this is to adopt a 'constitution theory' and claim that although there are two physical objects, they share the same matter and the same space. They are nevertheless distinct, however, because it is possible that one could exist when the other does not.I argue that the psychological criterion is not compatible with the constitution theory. For one thing, according to the psychological criterion the existence conditions of people are psychological, but the existence conditions of physical objects are not. I also point out that the psychological criterion allows that people can 'body-swap', but it does not make sense to suppose that a physical object can body-swap.I develop instead an alternative version of the psychological criterion, according to which a person is a series of mental states and events. I then show that on this theory, that while a person is not literally a substance, a person is nevertheless an entity that exists in a way that is akin to the way that substances exist. Such an entity I call a 'quasi-substance'.I also defend the psychological criterion against a number of objections to it, but I finish by developing a significant new problem for it. Certain influential psychological theorists wish downgrade the importance of continued existence in favour of what they say is 'what matters in survival', which they claim is 'Relation R'. R is defined as being 'psychological connectedness and/or continuity', and they wish to make R, unlike continued existence, a matter of degree. I argue, however, that there are various interpretations of what 'psychological connectedness and/or continuity' mean, and that none of them are consistent with the principle that since what matters in survival is of great significance, whether we have what matters in survival cannot depend on a trivial fact, a principle which is used (and required) by this sort of psychological theorist.