Abstract

Prof. Ruth Barcan Marcus created quantified modal logic in 1946. She extended the Lewis calculus S2 to cover quantification. Quantified modal logic became an essential tool for the rigorous study of natural language in the hands of R. Montague in the late sixties. Some complex phenomena cannot be properly handled at the level of sentences. Recent researches in formal semantics have concentrated on discourse and led to a rich amount of results. Logical theories introduced for the logical study of programs play an important role in these developments. We shall present a detailed account of the connection between dynamic logic and “static” logic. The core of the paper will be the translation of dynamic logic into S5. Developping an insight due to Prof. J. van Eijck, We shall offer a simplified version of the latter translation. The paper also relates to P. Gärdenfors' Knowledge in Flux