Leon Chwistek (1884–1944) was one of the most emblematic personalities of the interwar period in Poland. His versatile interests were manifested in as varied disciplines as philosophy, mathematics, logics, art, and literature. To philosophy he contributed with the theory of plurality of realities, and to art with two original artistic trends: zonism and motivism. Born in Zakopane, he spent most of his life in Krakow, where he was well known as an avant-garde intellectual and member of the artistic group called the Formists. In the 1930s he moved to Lvov, where he was appointed to the chair of philosophy at the University of Jan Kazimierz. After the outbreak of the World War II, he remained in Soviet-occupied Lvov, and in 1941, after the German invasion of the Soviet Union, he fled first to Georgia and then to Moscow, where he participated in the formation of the Union of Polish Patriots. Karol Chrobak is assistant professor in the Department of Philosophy at the Warsaw University of Life Sciences SGGW. His main field of interest is Polish and German contemporary philosophy. His PhD thesis was about Leon Chwistek’s critical rationalism (Niejedna rzeczywistość. Racjonalizm krytyczny Leona Chwistka, published in Polish in 2004) and his Habilitation thesis treated Helmuth Plessner’s philosophical anthropology (Między naturą a kulturą. Filozofia życia Helmutha Plessnera, published in Polish in 2014).