This paper introduces the Principle of Ontological Consistency as a criterion for evaluating theoretical validity. It argues that a theoretical framework is rendered invalid not solely by internal logical contradiction, but by structural misalignment with objective reality. While logical inconsistency constitutes a failure of internal coherence, ontological inconsistency arises when a theory, though internally consistent, posits a configuration of elements that reality does not instantiate. The paper distinguishes between logical inconsistency and ontological inconsistency, formalizes the concept of latent misalignment, and reinterprets empirical falsification as the delayed detection of preexisting structural discordance. Reality is treated not merely as an empirical dataset but as a meta constraint that governs the permissible structural relations within existence. On this account, truth is defined as structural congruence with reality, and error as structural misalignment. By elevating ontological alignment above formal coherence, the Principle of Ontological Consistency provides a framework for reassessing scientific theories, clarifying the distinction between incompleteness and failure, and addressing the limits of vacuous formal systems.