In this article, the author attempts to identify the sources of good and evil as undertaken by the Lvov-Warsaw School of Philosophy (LWSP) founded by Kazimierz Twardowski. Such attempts were undertaken by both Twardowski himself and his closest students and associates; Władysław Witwicki, Tadeusz Kotarbiński. Tadeusz Czeżowski, and Kazimierz Ajdukiewicz. The best-known approach is Kotarbiński’s independent ethics in which the author refers to Aristotle perceiving such potential in the characteristics of each individual as to distinguish elementary qualities in the form of opposites including opposition to good and evil. According to this approach, man acts in an evil manner because he stops following the natural voice of his own heart and instead implements set proposals provided by external factors. In the opinion of the author, the proposals formulated within the LWSP can form the basis for a rational explanation of the atrocities committed during World War II which modern ethics, being focused on neutral metaethical issues, fails to do.