Stanisław Leśniewski

Stanisław Leśniewski (March 30, 1886 – May 13, 1939) was a Polish mathematician, philosopher and logician.

Leśniewski went to a high school in Irkutsk. Later he attended lectures by Hans Cornelius at the Ludwig Maximilian University of Munich and lectures by Wacław Sierpiński at the Lviv University.

Life

Leśniewski belonged to the first generation of the Lwów-Warsaw School of logic founded by Kazimierz Twardowski. Together with Alfred Tarski and Jan Łukasiewicz, he formed the troika, which made the University of Warsaw, during the Interbellum, perhaps the most important research center in the world for formal logic.

His main contribution was the construction of three nested formal systems, to which he gave the Greek-derived names of protothetic, ontology, and mereology. ("Calculus of names" is sometimes used instead of ontology, a term widely employed in metaphysics in a very different sense.) A good textbook presentation of these systems is Simons (1987), who compares and contrasts them with the variants of mereology, more popular nowadays, descending from the calculus of individuals of Leonard and Goodman. Simons clarifies something that is very difficult to determine by reading Leśniewski and his students, namely that Polish mereology is a first-order theory isomorphic to what is now called classical extensional mereology.