or Stanis 0142; aw Leshniewski
born March 30, 1886, Serpukhov, Russia
died May 13, 1939, Warsaw
Polish logician and mathematician.
As a professor at the University of Warsaw (191939), he became a cofounder and leading representative of the Warsaw school of logic. His distinctive contribution was the construction of three interrelated formal system s, to which he gave the Greek-derived names of protothetic, ontology, and mereology .