The Psychological Approach to Personal Identity: Non-Branching and the Individuation of Person Stages

Abstract

We begin by discussing some logical constraints on the psychological approach to personal identity. We consider a problem for the psychological approach that arises in fission cases. The problem engenders the need for a non-branching clause in a psychological account of the co-personality relation. We look at some difficulties in formulating such a clause. We end by rejecting a recently proposed formulation of non-branching. Our criticism of the formulation raises some interesting questions about the individuation of person stages. RÉSUMÉ : Ce travail traite d'abord de certaines contraintes logiques concernant l'usage de l'approche psychologique pour définir l'identité personnelle. Nous y examinons un problème touchant l'approche psychologique dans les cas de fission. Ce problème exige l'intervention d'une clause qui nie tout recours au branchement dans l'examen de la relation de co-personnalité. Nous avons rencontré certaines difficultés dans la formulation d'une telle clause. Pour conclure, nous rejetons une formulation récente du non-branchement. Notre objection à cette formulation soulève quelques questions intéressantes concernant l'individuation de stades temporels personnels.

Four-Dimensional Animalism

“…Four-Dimensionalists usually qualify the criterion of psychological continuity for cases involving fission and fusion so the result is that there are two distinct persons continuous with the same earlier stage. They do so by insisting that psychologically continuous x and y are stages of the same person if there is no stage z that is psychologically continuous with x or y but simultaneous and distinct from either y or x [1]. So during the exam there are two streams of thought that have stages that are simultaneous but distinct from each other, thus ensuring that there is not a single person despite their both being psychologically continuous with shared earlier stages.…”

“…The Four-Dimensionalist recognizes the existence of entities, temporal parts, that the Three-Dimensionalist does not. 1 Your animal will have a temporal part that exists for the first half of its life, another for the first quarter, and even one for the first moment of its life. And your animal will consist of an infinite number of other temporal parts: some composed of only minimally conscious temporal parts, others containing just robustly self-conscious temporal parts, and still others including both thinking and non-thinking temporal parts.…”

“…I will contest this claim of non-identity, but without rejecting anything else in Hudson's conception of Four-Dimensionalism. 2 So I will accept, though just for the sake of argument, that we persist in virtue of temporal parts, that 1 Informally, a temporal part of an entity will exist only at a time and will then overlap all of the entity's other parts that exist at that time. More formally: something is a temporal part of x during interval T if and only if (i) the object exists at but only at times in T, (ii) it's part of x at every time during T, and (iii) at every moment during T it overlaps everything that's part of x at that moment [6, p. 59].…”

Endurantism and the Psychological Approach to Personal Identity

“…For discussion of the non‐branching clause, see Brueckner (2005). See also Brueckner and Buford (forthcoming).…”