Towards a Proof-Theoretic Analysis of Incorrect/Incomplete Proofs

Abstract

We investigate the proof-theoretic structure of incorrect/incomplete proofs, that is, derivations containing syntactic errors or incomplete inferential steps that nonetheless preserve partial semantic validity. Building on Hilbert's epsilon calculus, we formalize how such derivations can be corrected through semantic projection and weakest preconditions, leading to valid Herbrand disjunctions. We show that the epsilon calculus provides a natural framework for analyzing tolerance of falsity in proofs and for identifying conditions under which an incorrect proof can be semantically repaired. This approach extends Hilbert's program beyond correctness, toward a logic of error and recovery. Moreover we show that the extended first epsilon theorem is false-tolerant.