Stanisław Jaśkowski was a Polish

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 logician who made important contributions to proof theory

Proof theory

Proof theory is a branch of mathematical logic that represents proofs as formal mathematical objects, facilitating their analysis by mathematical techniques. Proofs are typically presented as inductively-defined data structures such as plain lists, boxed lists, or trees, which are constructed...

 and formal semantics. He was a student of Jan Łukasiewicz and a member of the Lwów–Warsaw School of Logic

Lwów–Warsaw School of Logic

The Lwów–Warsaw School of Logic was headed by Kazimierz Twardowski, who had been a student of Franz Brentano and is regarded as the "father of Polish logic."-History:...

. Upon his death his name was added to the Genius Wall of fame. He was the President (rector) of the Nicolaus Copernicus University in Toruń

Torun

Toruń is an ancient city in northern Poland, on the Vistula River. Its population is more than 205,934 as of June 2009. Toruń is one of the oldest cities in Poland. The medieval old town of Toruń is the birthplace of the astronomer Nicolaus Copernicus....

.

Jaśkowski is considered to be one of the founders of natural deduction

Natural deduction

In logic and proof theory, natural deduction is a kind of proof calculus in which logical reasoning is expressed by inference rules closely related to the "natural" way of reasoning...

, which he discovered independently of Gerhard Gentzen

Gerhard Gentzen

Gerhard Karl Erich Gentzen was a German mathematician and logician. He had his major contributions in the foundations of mathematics, proof theory, especially on natural deduction and sequent calculus...

 in the 1930s. (Gentzen's approach became more popular.) He was also one of the first, if not the first, to propose a formal calculus of inconsistency-tolerant (or paraconsistent) logic

Paraconsistent logic

A paraconsistent logic is a logical system that attempts to deal with contradictions in a discriminating way. Alternatively, paraconsistent logic is the subfield of logic that is concerned with studying and developing paraconsistent systems of logic.Inconsistency-tolerant logics have been...

. Furthermore, Jaśkowski was a pioneer in the investigation of both intuitionistic logic

Intuitionistic logic

Intuitionistic logic, or constructive logic, is a symbolic logic system differing from classical logic in its definition of the meaning of a statement being true. In classical logic, all well-formed statements are assumed to be either true or false, even if we do not have a proof of either...

 and free logic

Free logic

A free logic is a logic with fewer existential presuppositions than classical logic. Free logics may allow for terms that do not denote any object. Free logics may also allow models that have an empty domain...

.

Works

• On the Rules of Suppositions in Formal Logic Studia Logica 1, 1934 pp. 5-32 (reprinted in: Storrs McCall (ed.), Polish logic 1920-1939, Oxford University Press, 1967 pp. 232-258
• Investigations into the System of Intuitionist Logic 1936 (translated in: Storrs McCall (ed.), Polish logic 1920-1939, Oxford University Press, 1967 pp. 259-263
• A propositional Calculus for Inconsistent Deductive Systems 1948 (reprinted in: Studia Logica, 24 1969, pp 143-157 and in: Logic and Logical Philosophy 7, 1999 pp. 35-56)
• On the Discussive Conjunction in the Propositional Calculus for Inconsistent Deductive Systems 1949 (reprinted in: Logic and Logical Philosophy 7, 1999 pp. 57–59)
• On Formulas in which no Individual Variable occurs more than Twice, Journal of Symbolic Logic, 31, 1966, pp. 1-6

External links

• Polish Logic of the Postwar Period