A Non-Arbitrary Condition of Existence and Its Physical Projections

Contemporary physical theories exhibit an increasing reliance on external assumptions, imposed structures, and procedural fixes in order to achieve empirical adequacy. While such practices are often justified pragmatically, they raise a more fundamental question: under what conditions does a theoretical construction qualify as a well-defined object rather than as a contingent modeling procedure? This work proposes a non-arbitrary criterion of existence based on the notion of internal closure. A system is said to exist as an object only if its defining structures, interactions, and stability conditions are generated internally, without recourse to externally imposed operators, symmetries, tuning procedures, or interpretative supplements. Lack of closure implies non-uniqueness, path dependence, or representational ambiguity, all of which undermine objecthood independently of empirical success. The criterion is formulated at an abstract level and then examined through its conceptual projections in quantum mechanics, quantum field theory, spacetime structure, and biological systems. In each domain, it is shown that many successful frameworks function as effective descriptions while failing to satisfy minimal conditions of ontological closure. The analysis does not propose an alternative dynamical theory, but rather a restriction on admissibility: only closed constructions can meaningfully support claims of fundamental existence. By separating existence from performance, the paper aims to clarify the ontological status of theoretical models and to provide a domain-independent benchmark for foundational analysis in the philosophy of science.