 Another leading thinker of the period, active on the borderlines of sociology and philosophy, in both Poland and the United States, was Florian Znaniecki (1882–1958).In the interbellum, the philosopher members of the Polish Academy of Learning included Władysław Heinrich (1869–1957; Kraków), Kazimierz Twardowski (1866–1938; Lwów), Leon Petrażycki (1867–1931; Warsaw), and, from the following generation