Aristotelian and Stoic Syllogistic in the Anonymous Commentary on Plato’s Theaetetus

The present paper investigates the question as to how and for what purposes the Middle Platonic author of the Anonymous Commentary on Plato’s Theaetetus uses Aristotelian and Stoic syllogistic in his interpretation of the Platonic text. This investigation shows that the commentator employs Aristotelian categorical syllogistic as an exegetical tool for reconstructing arguments in the Platonic text, enabling him not only to uncover doctrinal statements that are in his view hidden in the Platonic text, but also to dissociate Plato from unwelcome propositions. By contrast, the commentator uses Stoic hypothetical syllogistic as a polemical tool for constructing ad hominem arguments against the Stoics. More precisely, the author exploits the Stoic type of deductive reasoning to draw anti-Stoic conclusions from premises that are accepted by the Stoics, and in doing so, he manages not only to refute Stoic doctrines, but also to corroborate the corresponding Platonic theories.