Stanisław Jaśkowski

Stanisław Jaśkowski (22 April 1906 – 16 November 1965) was a Polish logician and philosopher who made significant contributions to proof theory and formal semantics. He was a student of Jan Łukasiewicz and a prominent member of the Lwów–Warsaw School of Logic. Jaśkowski is widely regarded as one of the independent discoverers of natural deduction, a proof system he developed in the 1930s, concurrent with Gerhard Gentzen. His approach to natural deduction is noted for being closer to practical proof construction. He was also an early investigator into paraconsistent logic, also known as inconsistency-tolerant logic. His work extended to intuitionistic logic and free logic. Jaśkowski's academic career included positions at the University of Warsaw and later at the University of Toruń (now Nicolaus Copernicus University), where he served as the head of the Faculty of Mathematical Logic and as Rector from 1959 to 1962. He also collaborated with the Polish Academy of Sciences. He participated in the September Campaign during World War II and was briefly imprisoned. Jaśkowski died in Warsaw in 1965.