We prove, and mechanize in Rocq, an abstract obstruction theorem for closure predicates over the closed implication-falsity fragment . Evaluation completeness, , says that every formula-valued behavior of codes is represented up to closure equivalence, where abbreviates . For any closed under modus ponens and satisfying consistency, this completeness principle is incompatible with the internal excluded-middle schema , namely . Thus , and cannot hold jointly. The proof uses evaluation completeness to obtain a formula such that . Applying to this , either alternative gives by detachment, contradicting consistency. Consequently, any Boolean decision procedure for induces the obstructed excluded-middle schema. Mere refutation behaves differently: its false branch carries no closure condition, and is therefore inhabited by the always-false classifier.

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