6.9 Failure modes

Four failures should remain distinct:

1. underdetermination: multiple query-inequivalent hypotheses fit the available transcript;

2. ineffectivity: an admissible lift exists but the learner lacks a realizer that can find it;

3. realization defect: the doctrine is adequate, but the current model or gluing data must change; and

4. doctrinal obstruction: no adequate realization exists in the current categorical prior.

Only the fourth licenses revision of the language of possible worlds. This separation will later prevent a failed decision optimizer from being misdiagnosed as evidence against the learned world itself.