The Gettier Case File: Knowledge as an Earned Verdict

For twenty-four centuries knowledge was defined as justified true belief(JTB). In 1963 Edmund Gettier showed, in three pages, that a belief can bejustified, true — and still not knowledge; epistemology has been hunting a"fourth condition" ever since. This paper runs both of Gettier's canonicalcases (the sheep in the field; the ten coins) through an executable logicalinstrument — the ZTL judge, which returns not a bare verdict but the pairverdict + warranty, together with a named list of weak links. Findings: (1) a Gettier case is not a defect of inference but contraband atadmission — the "justification" of JTB is a T admitted on a witness thattestifies about a different atom; the logic, handed a poisoned marking,honestly answers "earned", because the fraud happens before it; (2) thecase has a measurable signature — the set of atoms carrying the verdictunder the naive marking and the set carrying it after the world'scorrection are disjoint, so "the truth arrived by a different road than thejustification" turns from metaphor into a checkable condition on two sets;(3) the passport office of the ZTL corpus confirms that no paradox ispresent — only a conditional refusal with a named culprit. The diagnosis is credited where it belongs: Sergei Artemov formalizedGettier's case in Justification Logic in 2008, and his formulation isquoted verbatim. The contribution here is an independent corroboration in aforeign formalism (the convergence between formal methods that Williamsonexplicitly recommends), executability (every claim of the paper re-checkswith one command: python3 zgettier.py, expedition E36 of the ZTLrepository), and three deltas along cracks Artemov himself named: amechanical admission gate instead of post-hoc analysis, a warranty ladderinstead of a timeless factivity axiom, and epochs instead of absent time.The jurisdiction boundary is measured and declared: fake-barn cases are notcaught by the signature, and the paper shows why that refusal is correct. Reproducibility: the reference bench zgettier.py (asserts pinned; a failingassert refutes the paper) ships in the public repositoryhttps://github.com/inventor1975/ZTL; the appendix is the verbatim output ofthe bench at the publication commit. The interactive studio(https://ztl.vitalyreznik.com) runs the same core in the browser. AI disclosure: this work was carried out with the substantialparticipation of the AI system Claude Fable 5 (Anthropic) under theVariant A collaboration model — the human sets the tasks, verifies theresults, and answers for the content. Per COPE/ICMJE recommendations theAI system is not listed as an author; the human author bears fullresponsibility.