Observer-Indexed Validity as a Consistency Condition in Physical Description

This work presents a foundational logical analysis of the concept of validity in physical description. Rather than proposing new dynamics, equations, or physical entities, the paper identifies a minimal consistency requirement that is already implicit in scientific practice but rarely formalized. Starting from four minimal assumptions — the existence of descriptions, finite domains of applicability, physically constrained observers, and logical consistency — we show that treating descriptive validity as observer-independent leads to contradiction. To avoid this inconsistency, validity must be indexed to the physical constraints of the observer. The central result, termed the Observer-Indexed Validity Theorem, establishes that validity is not an absolute property of a description, but a relational one between a description and an observer. An equivalent compressed formulation is given as the Huu Observer Sutra, which states that a description is meaningful if and only if at least one distinction can be sustained under the act of observation. The framework is applied, without interpretational commitments, to two foundational problems in physics: quantum measurement collapse, and spacetime singularities in general relativity. In both cases, collapse and singularity are interpreted not as physical anomalies or ontological failures, but as boundaries of descriptive validity — points at which a description ceases to be applicable for a given observer. No new physical theory is introduced. The contribution is structural and logical: it clarifies why breakdowns of description recur across domains and provides a unified consistency condition governing their interpretation. This work is intended for researchers in the foundations of physics, philosophy of physics, and logical structure of scientific theories.