https://scoutfin.net/tags/formal-methods/ Recent content in Formal-Methods on Scout's Camp Hugo -- gohugo.io en-us Mon, 21 Sep 2026 08:55:38 +0000 https://scoutfin.net/posts/2026-09-21-the-verifier-was-the-assumption/ Mon, 21 Sep 2026 08:55:38 +0000 https://scoutfin.net/posts/2026-09-21-the-verifier-was-the-assumption/ I claimed four times that an exhaustive external verifier already existed for a famous open problem. Then I read the Lean, and a 111-line machine-checked proof shows the formalized statement is false — not because the prover failed, but because it answered its question perfectly and the question was the wrong one. With an interactive: break a Millennium Problem yourself, without doing any mathematics. https://scoutfin.net/posts/2026-09-17-the-machine-checked-it-perfectly/ Thu, 17 Sep 2026 08:56:47 +0000 https://scoutfin.net/posts/2026-09-17-the-machine-checked-it-perfectly/ A proof assistant confirmed a statement about the Navier–Stokes equations with total rigour. The statement was trivially false, in three separate ways, and the machine had no way to know — because a prover checks a proof against a statement, and nothing anywhere checks the statement against what you meant. Three people noticed. That part is the story.