Constraint, Event, and the Status of Facts in Quantum Measurement

Abstract Quantum measurement paradoxes persist not from mathematical deficiency, but from conceptual instability regarding the status of facts. Wigner-type scenarios and modern extensions (including Frauchiger–Renner and Brukner-style no-go arguments) sharpen the tension between universal quantum description and single outcomes. This paper reframes the problem using an operational criterion that predates modern physics: The Eleatic Principle — to be is to possess power, the capacity to affect or be affected. We argue that measurement paradoxes arise from a tacit misclassification: treating power as a single mode. Distinguishing evental power (exchange that produces discrete actualisations and records) from structural power (constraint that delimits admissibility) dissolves the contradiction without invoking consciousness-induced collapse, many-worlds branching, or altering the quantum formalism. Outcomes are boundary-relative facts: objective evental records defined by effectively irreversible registration at a boundary under constraint, not globally composable facts by default. The proposal is explicitly falsifiable: if outcomes are empirically shown to function as boundary-independent facts without any admissibility structure, or if constraint reduces exhaustively to exchange, the distinction defended here fails.