Although Twardowski was not a logician and did not consider himself as such, his program formed a friendly environment for logic in all its subdomains: formal logic, semantics and methodology of science. Jan Łukasiewicz (1878–1956) was the first of Twardowski’s students to be interested in logic. He began his lectures in logic in Lvov in 1906. Kazimierz Ajdukiewicz (1890–1963), Tadeusz Czeżowski (1889–1981), Tadeusz Kotarbiński (1886–1981) and Zygmunt Zawirski (1882–1948) studied mainly under Twardowski, but they also attended courses conducted by Łukasiewicz. Stanisław Leśniewski (1886–1939) joined this circle in 1910. Warsaw appeared on the stage exactly in 1915, when the University of Warsaw was reopened. The academic staff was mainly imported from Lvov; Łukasiewicz was appointed professor of philosophy.