John Buridan on Non-contingency Syllogisms

Abstract

Whereas most of his predecessors attempted to make sense of, and if necessary correct, Aristotle’s theory of the modal syllogism, John Buridan starts afresh in his Treatise on Consequences, treating separately of composite and divided modals, then of syllogisms of necessity, possibility, and with mixed premises. Finally, he comes in the penultimate chapter of the treatise, Book IV Chap. 3, to present a concise treatment of syllogisms with premises of contingency, that is, two-sided possibility. The previous modal syllogisms had all been taken with an affirmed mode only, since modal conversion equates negated necessity and possibility with affirmed possibility and necessity, respectively. But in his Conclusions concerning syllogisms of contingency, he also treats those with negated mode. These are the non-contingency syllogisms.