A causal analysis of modal syllogisms

It is well known that in his Prior Analysis, Aristotle presents the system of syllogisms. Although many commentators consider Aristotle’s system of modal syllogisms almost impossible to understand from a modern point of view or even inconsistent, many philosophers still tried to account for these claims by looking for a consistent semantics of it. In this paper we will argue for a causal analysis of modal categorical sentences based on the notion of causal power. According to Cheng (1997), the causal power of A to produce B can be measured probabilistically. Based on Cheng’s hypothesis, we will derive a qualitative semantics for modal categorical sentences. We will argue that our approach fits well with Aristotle’s analysis of real definition in the Posterior Analytics, and that in this way we can account in a relatively straightforward way (using just Venn diagrams) for several puzzling aspects of Aristotle’s system of modal syllogisms.