The Law of Phase-Space Constructibility

This paper introduces a foundational principle for determining when mathematical descriptions in physics correspond to physically real systems. The proposed Law of Phase-Space Constructibility states that a region of phase space qualifies as physically meaningful only if it can be dynamically generated, traversed, and perturbed by the lawful evolution of the system itself.We apply this criterion to several longstanding frameworks in physics—including point particle mechanics, the second law of thermodynamics, and parity violation in weak interactions—and argue that the conceptual difficulties surrounding these cases arise from attributing physical significance to structures that lack internal coherence and dynamical accessibility.Rather than offering new mathematical formulations, the law provides an ontological boundary: not all that is mathematically definable should be treated as physically existent. This reintroduces a necessary distinction between symbolic representation and constructible structure, between predictive utility and ontological legitimacy.By recovering the forgotten question of what it means for a physical state to exist, the law challenges the unchecked expansion of physical models and offers a framework for evaluating which concepts belong in the domain of scientific reality. It does not restrict inquiry—it clarifies its scope.