 Łukasiewicz’s understanding of Aristotle’s syllogistic is based on two specific interpretative principles and a general attitude. The first principle is that Aristotle’s syllogisms are not, as had traditionally been supposed, inference schemata, of the form ‘p, q, therefore r’, but conditional propositions of the form ‘if p and q, then r’. This leads directly into the second principle, which is that there is behind the syllogistic treatment of term logic a deeper logic, that of propositions, and in particular a logic of opposition, ‘and’ and ‘if’, as well as (in modal syllogistic) ‘necessarily’ and ‘possibly’. Łukasiewicz takes this propositional basis to be occasionally invoked by Aristotle, for instance in the treatment of indirect proofs, but for the most part left as tacit, and he therefore regards it as legitimate to criticise Aristotle (unlike the Stoics) for not explicitly formulating the underlying propositional logic. Łukasiewicz’s trenchant and controversial views sparked a controversy over how to interpret the syllogistic. While the principles did win an early adherent in Patzig (1968), subsequent criticisms by Corcoran (1972, 1974) and, independently, Smiley (1974) established clearly that syllogisms are not propositions but inferences, and that Aristotle had no need of a prior logic of propositions. That view is now universal among scholars of Aristotle’s logic. In retrospect, it appears that Łukasiewicz was keen to wish onto Aristotle his own (Fregean) view of logic as a system of theorems based on a propositional logic.