Applicability Conditions in Fundamental Physics: A Necessity Argument from Persistent Failure Patterns

This paper identifies a cross-domain recurrence of the same structural failure patterns in cosmological origin proposals, quantum-mechanical interpretations, and foundational finality claims. The pathology is the same in each case: physical claims presuppose framework-constitutive conditions — licensing conditions — that they neither declare nor classify, and the resulting problems are not resolvable by the tools the claims themselves provide.Two structural limits explain why these patterns persist. First, a Structural Boundary Result establishes that no physical theory can fully derive its own licensing conditions: every self-licensing attempt terminates in postulate, circle, or frame-exit. Second, the major assessment frameworks in philosophy of science (Kuhn, Lakatos, Laudan, Dawid) operate at theory-level and do not provide claim-level diagnostics with regime-binding, auditable verdicts, or reformulation directives.From these two limits, a necessity argument follows: a methodological layer that makes licensing conditions explicit, classifiable, and auditable is structurally required. The paper specifies this layer — applicability diagnostics — as methodological infrastructure analogous to metrology. A six-step diagnostic procedure is defined and demonstrated on a worked example (Hartle–Hawking no-boundary proposal), producing a determinate verdict, a trigger report, and a reformulation directive. A fourteen-case Master Table applies seven diagnostic signatures (S1–S7) across cosmology, quantum mechanics, and foundational physics.The constraints identified are necessary, not sufficient: they define a diagnostic threshold, not a success criterion.