What does demonology have to do with logic?

I recently found out (through falling into a research rabbit hole courtesy of wikipedia, that James I/VI wrote a book on demonology. Never one to let a sound and orderly research programme get in the way of interesting side-projects, I downloaded a copy from Project Gutenberg and started reading. Almost immediately my decision was rewarded, for on the first page of the first chapter of the first book, one of the two people involved in the dialogue (namely, Epistemon) notes that “for as it is said in the logick schools, Contra negantem principia non est disputandum” (p. 4).

Oh! There’s logic in here! That’s an…interesting principle. I’m not sure I’ve heard of it before. I wonder where James found it. Turns out, wikipedia even has an article specifically on this maxim, noting that it is a principle of law and logic, which — nevertheless — is not found in Aristotle. The only medieval citation to it in the article is Duns Scotus’s commentary on Peter Lombard’s Sentences [1]. It’s certainly a reasonable principle, but it’s certainly not a commonly-specified logical principle. Interestingly, in googlebooks, most of the citations I found were from the 19th century, though I did find it in one law book from 1749, The Grounds and Rudiments of Law and Equity, Alphabetically Digested, by a “Gentleman of the Middle Temple”.

Of the remainder of the references I found to this principle in googlebooks, there were four from the 17th C: one in Dutch, one in German, one in Polish, and one in English. There was only one dated from before James’s treatise: Christlicher, warhafftiger Bericht auff und wider die Schmecherten und öffentliche Lügen eines Calvinischen Geistes, der sich nennet Georgium Lupichium Pfarrern zu Ambergk … wider D. Nicolaum Selneccerum …, a pamphlet published in Beyer in 1586, where on the final page, we are told “In Schuelen sagt man: contra negantem principia non est disputandem“.

The topic of “logick/logicque” comes up in one other place in James’s text, and is again found in Epistemon’s speech; he rebuts one of Philomathes’s arguments that there is no such thing as witchcraft or witches with the following:

As to the other reasone, which seemes to be of greater weight, if it were formed in a Syllogisme; it behooued to be in manie termes, and full of fallacies (to speake in termes of Logicque) for first, that that generall proposition; affirming Moyses to be taught in all the sciences of the Ægyptians, should conclude that he was taught in Magie, I see no necessity (pp. 21-22).

So there you have it…logic and witchcraft all in one go.


[1] Joannis Duns Scoti doctoris subtilis, ordinis minorum opera omnia, editio nova, vol. 16, Paris, 1894, p. 93.

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1 Response to What does demonology have to do with logic?

  1. Pingback: Dissensus profundus | The Non Sequitur

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