The extent to which a theory or model accurately represents and organizes observed phenomena and empirical data within its claimed domain, without committing to the theory's correctness regarding unobservable entities or ontological claims beyond those observations.

Principle

Empirical adequacy is satisfied when a theory’s observable‑level predictions correspond to data across the relevant tests; multiple empirically adequate theories can differ in unobservable commitments.

Demonstration

Illustrative scenario — Situation: Two quantum interpretations produce identical experimental statistics for a given set of measurements. Recognition: Both are judged empirically adequate because they recover the observed distributions. Action: Practitioners use either interpretation for empirical work while debates about ontology continue. Consequence: Experimental practice proceeds based on empirical adequacy even though ontological consensus is unresolved.

Misapplication

Assuming empirical adequacy implies truth about unobservables — e.g., claiming that because a model fits all current observations it reveals the literal existence of its theoretical entities rather than being one empirically adequate description among alternatives.

Consequence

Empirical adequacy focuses attention on observable fit and keeps empirical testing central to theory appraisal; it allows pragmatically effective use of theories even amid ontological disagreement, but may leave metaphysical questions unsettled.

Reversal

Empirical adequacy can be undermined by novel observations outside the tested domain or by previously unnoticed experimental error; in addition, background assumptions and auxiliary hypotheses can alter whether a theory is judged adequate.

Boundary

Clearly within: A model whose predicted measurement distributions match observed frequencies across relevant experiments. Boundary case: A model fitting aggregated data but failing in certain controlled subconditions. Clearly outside: Metaphysical assertions or speculative narratives that are not constrained by, nor deliver testable claims about, observable data.

Semantic Tension

Instrumentalism ↔ Scientific Realism — empirical adequacy supports instrumental use of theories while leaving open whether theoretical terms refer to real entities.

Synthesis

Empirical adequacy is an epistemic criterion that separates observable agreement from ontological commitment: it legitimizes the use of models that work for predictions and explanations of data while highlighting that such success need not settle claims about unobservables.