Otto Weininger’s work entitled Sex and Character is an important text in the intellectual history of Viennese modernism of the fin de siècle period. The author makes a pessimistic diagnosis of modern culture, which, according to him, is infected by anti-cultural feminine values. With desperate passion, he looks for a way to heal this state of affairs and finds it in the project of male reorientation in culture. To make this plan a reality, he thoroughly redefines sex and gender. The aim of the article is to investigate various paradoxes and contradictions contained in this famous work.