Aristotle on Syllogisms ‘from a Hypothesis’

Abstract

In chapters 23 and 44 of Prior Analytics I, Aristotle discusses arguments ‘from a hypothesis’ and claims that these include the reductio-arguments. His descriptions in both chapters show that what direct and indirect arguments of this group have in common is that the ‘hypothesis’ is not a part of the argument, but either an agreement to the effect that a certain proposition will be accepted as proven if another proposition has been proven, or—in cases of reductio ad impossibile—a logical principle for which no explicit agreement is needed.