Tadeusz Marian Kotarbiński (; 31 March 1886 – 3 October 1981) was a Polish philosopher, logician and ethicist. A pupil of Kazimierz Twardowski, he was one of the most representative figures of the Lwów–Warsaw School, and a member of the Polish Academy of Learning (PAU) as well as the Polish Academy of Sciences (PAN). He developed philosophical theory called reism () and an ethical system called independent ethics. Kotarbiński also contributed significantly to the development of praxeology. Henryk Greniewski and Kazimierz Pasenkiewicz were doctoral students under Kotarbiński. Life Tadeusz Kotarbiński was born on 31 March 1886 in Warsaw, then Congress Poland, Russian Empire, into an artist's family. His father, Miłosz Kotarbiński, was a painter his mother, Ewa Koskowska, was a pianist and composer. His uncles were Józef Kotarbiński, an important figure in Polish theater circles, and Wilhelm Kotarbiński, a talented painter. Expelled from secondary school in 1905 for participating in a strike, Kotarbiński managed to graduate two years later. He studied first as an unenrolled student at Jagiellonian University in Kraków, attending mostly lectures on mathematics and physics; then architecture in Lviv and Darmstadt, to finally settle for studies in philosophy and classical philology at the University of Lviv. His professors were some of the most esteemed philosophers, logicians and mathematicians of his time: Kazimierz Twardowski, Jan Łukasiewicz, Władysław Witwicki and philologist Stanisław Witkowski. He received his PhD with the thesis Utilitarianism in the Ethics of Mill and Spencer in 1912. After graduation, he taught classical languages at Warsaw's Mikołaj Rey Gymnasium (secondary school). In 1918 he began a lecturing career in philosophy at Warsaw University; from 1929 to 1930 he was dean of humanities. In the interwar period, Kotarbiński was involved in social affairs. He actively fought against anti-semitism, ultranationalism and clericalism. He wrote mainly for the monthly "Racjonalista", an organ of the Polish Association of Freethinkers. During the persecution of students of Jewish origin at Polish universities, when right-wing organizations tried to designate separate sectors in lecture halls for non-Polish students, he jointly joined their protest, during which he conducted his lectures while standing. He was an opponent of the ghetto benches introduced at the University of Warsaw in 1937. In his activities, close to the left-wing and socialist groups, he was a member of the Polish Teachers' Union, being in the years 1937–1939 president of the Higher School Section. After World War II, along with other eminent