The Measurement Problem as a Closure Problem

The quantum measurement problem is usually posed as a trilemma: we cannot have unitarity, definite outcomes, and ontological minimality at once. This paper argues that the trilemma rests on a hidden assumption—that definiteness must be a property of the ontic wavefunction. That assumption is a category error. We show that definiteness is instead a structural property of operational records under admissible irreversible coarse–graining. Formally, admissible operations induce a quotient event algebra, and a “definite outcome” is a unique stable record class in this quotient. Once probabilities are required to descend to this structure, the Born rule emerges as the only positive additive measure compatible with closure. The result preserves global unitarity, yields definite recorded outcomes without added ontology, and provides a quantitative, falsifiable scaling law for macroscopic classicality. The measurement problem is thereby reframed as a closure problem on operational event geometry.