Łukasiewicz, Jan (1878–1956)

Before 1918, Łukasiewicz’s interests centred on logic (in the broad sense) and philosophy, and he worked on induction and probability. He also wrote an important historical book on the principle of contradiction in Aristotle. After 1918, Łukasiewicz concentrated almost entirely on mathematical logic and was the main organizer of the Warsaw School of Logic. The discovery of many-valued systems of logic is perhaps the most important result he achieved. He also invented an ingenious logical symbolism in which brackets (or other punctuation signs) are not necessary (bracket-free or Polish notation). Propositional calculi became a favourite topic of Łukasiewicz’s logical investigations. The history of logic was another subject in which Łukasiewicz achieved important results.