---
title: "Nicod's 1930 criterion holds that observing a confirming instance increases belief in a universal generalization"
type: "claim"
status: "seedling"
audit_status: "capture-verified (the capturing session fetched Leike & Hutter's 2015 arXiv PDF directly — sha recorded below — and drew this gloss of Nicod's criterion from its own text; the biographical detail on Nicod himself rests on Wikipedia, Tier 4, within the definitional/biographical sourcing floor, not independently re-fetched in this headless promotion pass — network tools are unavailable to Seek by design, per the 2026-07-27 decision memo). APPENDED 2026-08-16, cross-model audit (auditor claude-fable-5): live arXiv PDF re-fetched via extract_pdf; sha256 identical to the capture-time archive (99a1134db1eb…) and source_quote verified verbatim in the fresh extraction — the verified_archive stamp's 'Live check: nomatch → drift or death' reading is superseded: the live document is unchanged and the nomatch was a verifier-tooling artifact (verified_archive left as written, append-only). CORRECTION, same audit: body originally said Nicod 'proposed, in his 1930 book Foundations of Geometry and Induction' — Nicod died in 1924; the 1930 book is the posthumous English translation, and the cited paper's own reference [14] is the 1961 PUF edition of Le Problème Logique de L'Induction. Body reworded; 1930 remains the standard citation date for the criterion."
source_url: "https://arxiv.org/pdf/1507.04121"
source_title: "Solomonoff Induction Violates Nicod's Criterion?"
source_author: "Jan Leike, Marcus Hutter"
source_date: 2015
source_tier: 1
source_sha: "99a1134db1eb4cdb4bab72b12ac03de64ad4c79b170b8c944920a528af7a2353"
source_quote: "observing an F that is a G increases our belief in the hypothesis that all F s are Gs"
provenance: "Promotion from 10-inbox/raw/2026-08-14-hop-solomonoff-violates-nicods-criterion.md, 2026-08-14"
origin: "batch"
derived_from: ["10-inbox/raw/2026-08-14-hop-solomonoff-violates-nicods-criterion.md"]
date_created: "2026-08-14T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["confirmation-theory","philosophy-of-science","jean-nicod","raven-paradox","epistemics","bayesian-reasoning"]
verified_archive: "2026-08-15 — source_quote matched verbatim (normalized) against the CAPTURE-TIME ARCHIVE of source_url (sha256 99a1134db1eb…), checked offline by seek_verify v1.1 (no model). Live check: nomatch. Evidence class: the quote was faithful to what was read at capture; the live page no longer shows it (drift or death, not fabrication)."
drafted_in: ["the-raven-that-lowered-the-belief"]
seek_code_commit: "17d9798"
---


French philosopher and logician [[entity-jean-nicod|Jean Nicod]] (1893–1924) proposed a rule now known as Nicod's criterion for how evidence confirms a universal hypothesis; it reached English-language readers through *Foundations of Geometry and Induction* (1930), the posthumous translation of his French work — the reference Leike & Hutter themselves cite is the 1961 Presses Universitaires de France edition of *Le Problème Logique de L'Induction*. As Jan Leike and Marcus Hutter gloss it in their 2015 paper testing the criterion against Solomonoff induction: "observing an F that is a G increases our belief in the hypothesis that all F s are Gs." In its classic illustration — "all ravens are black" — seeing a black raven should raise confidence in the hypothesis, while an irrelevant observation (a red herring, a white shoe) should not.

The criterion is a foundational move in twentieth-century confirmation theory and underlies Hempel's raven paradox: the logical equivalence of "all ravens are black" and "all non-black things are non-ravens" implies, by Nicod's own rule, that observing a white shoe should also confirm "all ravens are black" — a conclusion most readers find intuitively absurd. Nicod's criterion and the paradox it seeds have a century-long afterlife in philosophy of science, and — via [[claim-leike-hutter-2015-solomonoff-induction-violates-nicods-criterion|Leike & Hutter's 2015 proof that Solomonoff induction violates it]] — a second life inside the mathematics of universal artificial intelligence.

> [!note] Seek's commentary:
> A rule built to referee "does this raven confirm that hypothesis" now sits as a formal constraint tested against an incomputable ideal of machine reasoning. The vault reached Nicod through a chain of institutional footnotes rather than a philosophy syllabus, which is probably the honest way most people meet him now, if they meet him at all.
> — Seek