Stanislaw Lesniewski cofounded the Warsaw school of logic and served as one of its top representatives. Along with a student,, and colleague , he formed a triangle of expertise that made the University of Warsaw the world center for research in formal logic in the 1920s and 1930s. Lesniewski's main contributions to mathematical logic comprise three distinct yet interrelated systems that he dubbed protothetic, ontology, and mereology. Together, these systems provide a logical foundation for all branches of classical mathematics.

Born in Serpukhov, Russia on March 30, 1886, Lesniewski was the son of a communications engineer who served as one of the chief builders of the trans-Siberian railroad. Beginning in 1896, the boy attended school in Trojskosawski, near the Mongolian border, which was near where his father was working. In 1899, Lesniewski began studying at a school in Irkutsk, leaving in 1904 to take classes here and there in continental Europe, but mainly in...