 They were initiated at Kraków by Ivan Śleszyński ("aka" Jan Śleszyński, "aka" Ivan Vladislavovich Sleshinsky; 23 July 1854 – 9 March 1931), professor of mathematics and logic.At Kraków also, and later at Lwów, logic studies were conducted by Leon Chwistek (1884–1944), a multi-faceted and somewhat eccentric thinker—mathematician, philosopher, esthetician, painter—whose name came to be associated popularly with his concept of "plural realities.