  Prior seems first to have learned of Łukasiewicz through the writings of his pupil Bochenski. Łukasiewicz had devised an axiomatic treatment of Aristotle’s reduction of the imperfect syllogistic moods to those of the first figure, which Prior encountered in Bochenski’s Précis. This enchanted Prior. He was taking his students through the derivations as early as 1951, and summarized Łukasiewicz’s system in the final chapter of The Craft. Throughout the chapter he made extensive use of Łukasiewicz’s symbolic notation.  It was Łukasiewicz’s axiomatic treatment of traditional logic that fully brought home to Prior the power of modern symbolic methods. Moreover, it was probably his reading of Łukasiewicz that made clear to him the fundamental importance of propositional logic. ‘It seems that Aristotle did not suspect the existence of another system of logic besides his theory of the syllogism’, Łukasiewicz had written, ‘[y]et he uses intuitively the laws of propositional logic …’ (1951a: 49). (Łukasiewicz’s axiomatisation of the syllogistic incorporated his own three-axiom formalization of propositional logic (1951a: 80).)