Irreflexivity and Aristotle's Syllogismos

Abstract

Aristotle's definition of syllogismos at Prior Analytics 24b18–20 specifies syllogistic consequence as an irreflexive relation: the conclusion must be different from each premise and any conjunction of the premises. Typically, commentators explain this irreflexivity condition as Aristotle's attempt to brand question-begging syllogismoi illegitimate in argumentative contexts. However, this explanation faces two problems. First, it fails to consider all the contexts in which Aristotle thinks syllogismoi are deployed. Secondly, irreflexivity rules out only some arguments that Aristotle considers question begging. Here I address these problems. First, I examine all the contexts in which Aristotle thinks syllogismoi can be used. Secondly, I argue that, for each context, irreflexivity makes sense as a condition, but for different reasons. Assuming that a condition which holds in each context is a condition on syllogistic consequence tout court, this explains why Aristotle holds syllogistic consequence to be an irreflexive relation.