Abstract

The problem of personal identity asks what constitutes the persistence of a person through time and change: what makes the person who wakes up tomorrow the same person who went to sleep tonight, despite the changes that occur during sleep, and despite the fact that the physical and psychological states that constitute a person at any moment differ from those that constituted them at earlier moments. The principal accounts divide between psychological continuity theories, biological continuity theories, and narrative theories, each of which captures genuine features of personal identity while facing well-known difficulties. Psychological continuity theories face the reduplication problem: if psychological continuity can in principle branch, it cannot be what constitutes identity, which is necessarily one-one. Biological continuity theories face the problem of accounting for the persistence of personal identity through radical psychological change. Narrative theories face the difficulty of specifying what makes a narrative mine without presupposing the personal identity they are supposed to explain. This paper proposes that Constraint Theory (CT) — the thesis, established by transcendental argument, that constraint is the ontological primitive constitutive of determinate existence as such — provides a principled account of personal identity that resolves the central difficulties while preserving what each major account gets right. On the CT account, a person is a constraint configuration: a dynamic but structured pattern of exclusion relations across cognitive, affective, embodied, and interpersonal dimensions that constitutes the person’s characteristic way of being in the world. Personal identity over time is the persistence of a characteristic constraint signature: not the preservation of specific psychological states but the continuity of the structural pattern of constraint relations that individuates this person from all others. The reduplication problem is dissolved: two continuants from a single branching origin diverge in their constraint signatures from the moment of branching and therefore constitute distinct persons from that point, not competing claimants to a single identity. The gradience of personal identity — the fact that it admits of degrees and borderline cases — is explained by the gradience of constraint-structural continuity. What matters in survival, on the CT account, is not identity per se but constraint-signature continuity, which vindicates and grounds Parfit’s revisionary conclusion without invoking psychological connectedness as a primitive. The paper develops implications for the ethics of personal identity, the constitution of persons through relationships, the developmental account of self-constitution, and disorders of personal identity.