Second-Order Coherence Science (SOCS) is a second-order epistemic boundary discipline concerned with the conditions under which systems preserve epistemic validity, orientability, and responsibility across time. It addresses a structural failure mode increasingly evident in scientific, technological, and institutional domains: the decoupling of functional stability from epistemic truthfulness under conditions of sustained drift. SOCS offers no empirical explanations, predictive models, optimization strategies, or governance frameworks. Its function is boundary articulation. It specifies conditions under which first-order systems may be evaluated with respect to epistemic validity rather than performance, efficiency, or local optimization. In this context, truthfulness denotes the capacity of a system to maintain coherent orientation under pressure, even as operational effectiveness persists. Ethical integrity is treated as a structural property rather than a normative demand. It concerns whether responsibility remains internal to a system’s reflexive scope or is displaced onto abstractions, metrics, procedures, or external agents. SOCS thereby distinguishes functional success from epistemic responsibility without proposing mechanisms for their reconciliation. This document defines the scope, conceptual structure, and explicit non-claims of SOCS. It introduces no operational methods, evaluative tools, or applications. The boundary draws on limiting principles from logic (Gödel), information theory and thermodynamics (Shannon, Prigogine), and cybernetics (Bateson); introduces core concepts such as epistemic drift, recursive degradation, semantic density, and the inalienability of responsibility; and explicitly delineates its non-collision with quantum optics, psychology (sense of coherence), and hardware engineering (system-on-a-chip). Academic citation is encouraged. Commercial, applied, or instrumental use requires explicit authorization.