The book contains anti-Latin writings of St. Gregory Palamas (1296–November 14, 1359), devoted to the question of the procession of the Holy Spirit: two “Apodictic Words” and the adjacent short work “Against Veccus”. Publication of these works, first translated into Russian language, significantly clarifies and expands the understanding of Russian readers about the argumentation of Orthodox theologians in their polemics with Roman Catholics on one of the most important controversial issues, as well as about the methodology of polemics itself. The book is intended for theologians, philosophers, historians and everyone interested in the fate of the Church.