On What Matters in Survival

Abstract

Faced with the question of what matters in survival, we have a choice of seemingly alternative answers. Let us use the term 'person-stage' as in recent articles by David Lewis and Derek Parfit, and let us, like them, call the relation between two person-stages which belong to the same person the 'I-relation'.' Our apparent alternatives are, then, the thesis that the I-relation is what matters (which common sense seems to suggest) and the view that what matters is a psychological relation between person-stages. An important argument for regarding the answers as alternatives is furnished by the case of fission. A person-stage S belongs to a person C. At a later date a person-stage S, belongs to a person C, and a contemporary but non-identical person-stage S2 belongs to C2. Following Lewis, let us call the psychological relation which, arguably, matters in survival (psychological continuity and/or connectedness) the 'R-relation'. Now suppose that S, and S2 are both R-related to S. Are they both I-related to S? It is commonly argued that they cannot be (by Parfit among others, in his i97i article on personal identity).2 Since identity is transitive and symmetrical it is natural to anticipate that the I-relation is transitive and symmetrical. So if S, and S2 are both I-related to S they will have to be I-related to each other. At least one of S, and S2, therefore, is apparently R-related to S without being I-related to S. The moral, allegedly, is that Rand I-relations are not coextensive, and thus cannot both be what matters in survival. Lewis, unlike Parfit, denies that the two answers to the question of what matters are rivals. According to him the I-relation is the same as the R-relation. He claims not only that a person is a maximal Iinterrelated aggregate of person-stages (I shall accept this without discussion, since it seems to be no more than is implicit in the idea of a person-stage), but also that it is a maximal R-interrelated aggregate of person-stages (Lewis, p. 22). He offers an ingenious treatment of the fission case which seeks to make it consistent with his claims. According to Lewis S is a stage of both C, and C2, but C, and C2 are not the same person. So S, and S2 are not I-related, even though they are both I-related to S. Although he believes that the I-relation is symmetrical, by claiming that it is not transitive he tries to undermine the argument summarized in the previous paragraph.3