Kazimierz Ajdukiewicz (12 December 1890 – 12 April 1963) was a Polish philosopher and logician, a prominent figure in the Lwów–Warsaw school of logic. He originated many novel ideas in semantics. Among these was categorial grammar, a highly flexible framework for the analysis of natural language syntax and (indirectly) semantics that remains a major influence on work in formal linguistics. Ajdukiewicz's fields of research were model theory and the philosophy of science. Source: Wikipedia (en)