Mackie on Personal Identity

Abstract

In his article, 'Personal Identity', Richard Swinburne defends a thesis that has been advocated previously by Bishop Butler and by Thomas Reid, namely that personal identity is something ultimate and unanalyzable, which cannot be said to 'consist' in anything beyond itself.l (I shall call this the 'irreducibility thesis'). Swinburne's position has recently come under attack by John Mackie in his book, Problems from Locke.2 Here I want to show that Mackie's reasons for rejecting the irreducibility thesis and for substituting his own theory in its place are not persuasive. Swinburne begins his argument by scrutinizing the theories which regard personal identity as constituted either entirely by bodily continuity or entirely by psychological continuity (principally memories) and finding each of them inadequate for familiar reasons. He then examines the more plausible varieties of 'empiricist theory' (an empiricist theory being any that takes personal identity to consist in continuity of some observable feature or features), namely those varieties that see personal identity as constituted by continuity of both psychological and physical characteristics, where such factors are to be weighted and balanced against each other according to rules provided by the particular theory in question. For example, some such 'combination' empiricist theory might claim that continuity of the brain or psychological continuity is a sufficient condition of personal identity (or perhaps that the former is always a necessary condition also), while specifying that either is sufficient only if no other person satisfies the other or both conditions simultaneously. And the theory will also specify what sort of decision about personal identity is to be made if another person does happen to satisfy the other or both conditions at the same time. Thus in a case of putative 'body exchange' the theory may say that the person with the original brain is identical with the preexchange person who had that brain, or that neither post-exchange person is identical with either pre-exchange person. Swinburne's strategy is to analyze and refute the main varieties of combination empiricist theory?primarily on the grounds that whether or not A survives as B is a fact which can never depend on a decision about how we are going to use words, as the empiricist theories would force us to maintain?leaving him with the conclusion that personal identity therefore cannot consist in continuity of one or more observable characteristics, since empiricist theories took all these into account. Continuity of body, memory and character is, to be sure, evidence of personal identity, but personal