Hypothetical Syllogisms and Infinite Regress

Abstract

In his commentary on Aristotle’s De interpretatione, Ammonius puts forward an argument for the priority of categorical over hypothetical syllogisms. The argument relies on two of the Five Modes of Agrippa, the modes from infinite regress and from hypothesis. Much of the argument, however, remains unclear and open to doubt. The present chapter sheds new light on the argument by considering it against the backdrop of two related arguments given by Pseudo-Ammonius and Alexander of Aphrodisias in their commentaries on the Prior Analytics. The chapter argues that all three arguments originate in Theophrastus’ discussion of Aristotle’s treatment of syllogisms from a hypothesis. They rely on the view that stating a hypothetical proposition If P, then Q does not amount to the unqualified assertion of a conditional proposition, but rather to a conditional assertion of Q on the supposition that P.