Stanisà Âaw Leà Âniewski (; 30 March 1886 â 13 May 1939) was a Polish mathematician, philosopher and logician. A professor of mathematics at the University of Warsaw, he was a leading representative of the LwówâÂÂWarsaw School of Logic and is known for coining and introducing the concept of mereology as part of a comprehensive framework for logic and mathematics.
Leà Âniewski was born on 28 March 1886 at Serpukhov, near Moscow, to father Izydor, an engineer working on the construction of the Trans-Siberian Railway, and mother Helena (née Palczewska). Leà Âniewski went to a high school in Irkutsk. Later he attended lectures by Hans Cornelius at the Ludwig Maximilian University of Munich and lectures by Wacà Âaw Sierpià Âski at Lviv University.
Leà Âniewski belonged to the first generation of the LwówâÂÂWarsaw School of logic founded by Kazimierz Twardowski. Together with Alfred Tarski and Jan à Âukasiewicz, he formed a trio 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 ("Calculus of names" is sometimes used instead of ontology, a term widely employed in metaphysics in a very different sense), and mereology, which, in its first, 1916, version introduced "the notion of collective class, a concrete notion of class elaborated by Leà Âniewski directly against CantorâÂÂs sets, FregeâÂÂs extensions of concepts and RussellâÂÂs and WhiteheadâÂÂs classes as incomplete symbols."
A good textbook presentation of these systems is that by 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 Leà Âniewski and his students, namely that Polish mereology is a first-order theory equivalent to what is now called classical extensional mereology (modulo choice of language).
While he did publish a fair body of work (Leà Âniewski, 1992, is his collected works in English translation), some of it in German, the leading language for mathematics of his day, his writings had limited impact because of their enigmatic style and highly idiosyncratic notation. Leà Âniewski was also a radical nominalist: he rejected axiomatic set theory at a time when that theory was in full flower. He pointed to Russell's paradox and the like in support of his rejection, and devised his three formal systems as a concrete alternative to set theory. Even though Alfred Tarski was his sole doctoral pupil, Leà Âniewski nevertheless strongly influenced an entire generation of Polish logicians and mathematicians via his teaching at the University of Warsaw. It is mainly thanks to the writings of his students (e.g., Srzednicki and Rickey 1984) that Leà Âniewski's thought is known.
During the PolishâÂÂSoviet War of 1919-21, Leà Âniewski served the cause of Poland's independence by breaking Soviet Russian ciphers for the Polish General Staff's Cipher Bureau.
Leà Âniewski died suddenly of cancer, shortly before the German invasion of Poland, which resulted in the destruction of his Nachlass. He was buried at Warsaw's Powàzki Cemetery.