The Measurement Problem Is an Individuation Problem - Record-Constituted Definiteness and the Ontological Incompleteness of Everett

This paper argues that the unresolved core of the measurement problem is not best understood as a purely dynamical problem. The standard formulation asks how linear quantum evolution yields a single definite outcome. That question is genuine, but it already presupposes that definiteness must be read directly from the global physical state. I argue instead that the deeper residual problem is one of individuation: under what conditions does a physically realized difference count as a fact, an outcome, or a world for a finite record-bearing system? Once the issue is formulated at this level, the role of decoherence looks different. Decoherence and redundant environmental encoding do not select one globally privileged outcome, but they do supply the physical architecture of stable, accessible, and update-constraining records. The remaining task is ontological rather than primarily dynamical. This diagnosis is especially significant for Everettian quantum mechanics. Everett preserves the global physics with unusual clarity, but branching structure alone does not determine when physically realized differences count as distinct observer-worlds for finite agents. A complete account therefore requires an explicit criterion of observer-world individuation. I propose such a criterion in terms of record-constituted definiteness: two physical configurations belong to the same observer-world for an agent when they agree with respect to the agent's accessible, persistent, and update-constraining records.