  Of the four technical papers that marked the explosive beginning of Prior’s career as a formal logician in 1952 (1952a-d), two concerned modal logic. ‘Modality De Dicto and Modality De Re’ is a discussion of this distinction as it appears in Aristotle, Ockham, and Peter of Spain, together with a comparison of these earlier views with those of von Wright in his 1951 book An Essay on Modal Logic. ‘In What Sense is Modal Logic Many-Valued?’ concerns Łukasiewicz’s four-valued matrices for modal logic. In this paper Prior took issue with the view ‘that the logic of modality cannot be satisfactorily studied unless we use a many-valued calculus for its formal expression’, and he proposed a subversive interpretation of the four-valued matrices according to which modal propositions remain bivalent. This paper was the curtain raiser to Prior’s extensive study of Łukasiewicz’s work on modality, and thereafter he read Łukasiewicz widely—even material in Polish, saying ‘the symbols are so illuminating that the fact that the text is incomprehensible doesn’t much matter’.