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 be
justified, true — and still not knowledge; epistemology has been hunting a
"fourth condition" ever since. This paper runs both of Gettier's canonical
cases (the sheep in the field; the ten coins) through an executable logical
instrument — the ZTL judge, which returns not a bare verdict but the pair
verdict + warranty, together with a named list of weak links.

Findings: (1) a Gettier case is not a defect of inference but contraband at
admission — the "justification" of JTB is a T admitted on a witness that
testifies about a different atom; the logic, handed a poisoned marking,
honestly answers "earned", because the fraud happens before it; (2) the
case has a measurable signature — the set of atoms carrying the verdict
under the naive marking and the set carrying it after the world's
correction are disjoint, so "the truth arrived by a different road than the
justification" turns from metaphor into a checkable condition on two sets;
(3) the passport office of the ZTL corpus confirms that no paradox is
present — only a conditional refusal with a named culprit.

The diagnosis is credited where it belongs: Sergei Artemov formalized
Gettier's case in Justification Logic in 2008, and his formulation is
quoted verbatim. The contribution here is an independent corroboration in a
foreign formalism (the convergence between formal methods that Williamson
explicitly recommends), executability (every claim of the paper re-checks
with one command: python3 zgettier.py, expedition E36 of the ZTL
repository), and three deltas along cracks Artemov himself named: a
mechanical admission gate instead of post-hoc analysis, a warranty ladder
instead of a timeless factivity axiom, and epochs instead of absent time.
The jurisdiction boundary is measured and declared: fake-barn cases are not
caught by the signature, and the paper shows why that refusal is correct.

Reproducibility: the reference bench zgettier.py (asserts pinned; a failing
assert refutes the paper) ships in the public repository
https://github.com/inventor1975/ZTL; the appendix is the verbatim output of
the 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 substantial
participation of the AI system Claude Fable 5 (Anthropic) under the
Variant A collaboration model — the human sets the tasks, verifies the
results, and answers for the content. Per COPE/ICMJE recommendations the
AI system is not listed as an author; the human author bears full
responsibility.