Polish logician and semanticist who was the chief contributor to the Warsaw school of philosophy and logic (logic, history of), which analyzed the relationship of language and knowledge. He is credited with developing in 1920 the first deductive theory for the study of logic based on syntax.

Obtaining a doctorate from the University of Lviv (Lvov), where he studied philosophy, physics, and mathematics, Ajdukiewicz lectured in philosophy at the universities of Lviv, Poznań, and Warsaw (1921–61). His principal works include Z metodologii nauk dedukcyjnych (1921; “On the Methodology of the Deductive Sciences”), articles in the periodical Studia Logica, and a collection of his articles from 1920 to 1939 and 1946 to 1964 entitled Język i poznanie, 2 vol. (1960–65; “Language and Knowledge”).