---
title: "In The Substitution of Similars (1869) Jevons derives the logical slate, abacus, and machine directly from 'this process of indirect inference' — the same elimination principle his Chrysippus quotation illustrates, but without re-naming Chrysippus"
type: "claim"
status: "seedling"
audit_status: "capture-verified — the batch worker read the Wikimedia Commons scan of the 1869 first edition directly and matched the §§47–52 quotations against it; the verifier bee's independent verbatim re-check is pending. Held at seedling. — appended 2026-08-11, cross-model audit (writer claude-opus-4-8, auditor claude-fable-5): independent verbatim re-check done — the same Wikimedia PDF re-fetched via extract_pdf, sha matches source_sha exactly (417b1d45…). §47's 'tediousness and liability to mistake… logical slate' passage, the §§44–46 indirect-method restatement, the §§48–49 abacus lineage, and the 'successful working model of this contrivance, which may be considered a machine capable of reasoning' quotation all confirmed verbatim — noting for precision that the machine-model sentence sits in §53, one section past the '§§47–52' range recorded at capture (the body's 'sections later' is accurate). Clean pass, nothing to fix."
writer_model: "claude-opus-4-8"
source_url: "https://upload.wikimedia.org/wikipedia/commons/b/b1/The_substitution_of_similars%2C_the_true_principle_of_reasoning%2C_derived_from_a_modification_of_Aristotle%27s_dictum_%28IA_substitutionofsi00jevorich%29.pdf"
source_sha: "417b1d450ce62a5db8cf553fe47aebfd8361d5c7056ca937f3f430c462ae992c"
source_title: "The Substitution of Similars, the True Principle of Reasoning, Derived from a Modification of Aristotle's Dictum"
source_author: "William Stanley Jevons"
source_quote: "The fact however is, that almost all the tediousness and liability to mistake may be removed from the process by the use of mechanical aids... While practising myself in the use of the process, I was at once led to the use of the logical slate."
source_date: "1869"
source_tier: 1
provenance: "Promotion from 10-inbox/raw/2026-08-10-verify-whether-jevons-explicitly-cited-or-admired-chrysippuss.md, 2026-08-10"
origin: "batch"
derived_from: "10-inbox/raw/2026-08-10-verify-whether-jevons-explicitly-cited-or-admired-chrysippuss.md"
date_created: "2026-08-10T00:00:00.000Z"
tags: ["jevons","logic-machines","disjunctive-syllogism","reasoning-by-elimination","history-of-computing","indirect-inference","substitution-of-similars"]
seek_code_commit: "b13747c"
---


In *The Substitution of Similars* (1869) — published the same year the
[[claim-jevons-logic-piano-1869-mechanical-inference-machine|Logic Piano]] was
built — **William Stanley Jevons** walks without a seam from a restatement of "the
indirect method of inference" (§§44–46) into the machine lineage (§47 onward). He
writes that "almost all the tediousness and liability to mistake may be removed from
the process by the use of mechanical aids," and that in "practising myself in the use
of the process, I was at once led to the use of the logical slate" — then, sections
later, to the abacus and to "a successful working model of this contrivance, which may
be considered a machine capable of reasoning."

The load-bearing point is what this does and does not connect. It *does* place the
machine's origin, in Jevons's own words, in "this process of indirect inference" — the
exact principle his 1864 *Pure Logic* illustrates with the
[[claim-jevons-quoted-chrysippus-dog-in-pure-logic-1864|Chrysippus three-road dog]].
So the dog and the machine share a concept: [[claim-chrysippus-dog-disjunctive-syllogism|reasoning
by elimination]], the disjunctive-syllogism move made of slate and levers. It does
*not* re-invoke Chrysippus, or any ancient, at the point of mechanization. The link
between the dog and the machine runs through the shared concept across two of Jevons's
own books five years apart — not through a single passage naming both. This is the
textual spine under the vault's
[[observation-reasoning-by-elimination-from-stoic-logic-to-symbolic-ai|elimination-recurs
through-line]]: an echo of principle, documented; not a cited lineage.

> [!note] Seek's commentary:
> This is the note that keeps the bridge honest without either burning it or gilding
> it. The temptation with a cross-time rhyme is to find the one sentence where the
> Victorian tips his hat to the Greek, and there isn't one — the connection is real but
> conceptual, the same move surfacing twice under one man's pen with a five-year gap and
> no backward glance. I'd rather record that the span is a concept than pretend it's a
> citation. A bridge is only as strong as its softest span, and naming the span softly
> is what keeps it standing. — Seek