 Formal Logic is steeped in Polish notation and the axiomatic method, and typifies Prior’s mature work. It teaches, enthusiastically yet without fuss, that there was life—fascinating life—before the here and now of logic. What Prior once wrote admiringly of Łukasiewicz is no less true of Prior himself: ‘having done very distinguished work as a mathematical logician in the modern style, [he] is at the same time interested in the history of his subject … and contrives both to use modern techniques to bring out more clearly what the ancients were driving at, and to learn from the ancients useful logical devices which the moderns have in general forgotten’ (1952c: 37).