The main task of this monograph is to reveal the influence of the ideas and practices of isikhasm on the formation of medieval Russian religious philosophy, the main representatives of which are Venerable Nil Sorsky and Maxim Grek. The mystical experience of holy silence and its philosophical and theological representation is considered in the context of Byzantine and medieval Russian culture. The main subjects of analysis are Isychasist epistemology in the framework of the theory of God-knowledge and Isychasist anthropology, the key problems of which are the concept of micro- and macrocosm, the doctrine of psychophysical unity of man with the leading role of the heart, a view of man as an image and likeness of God which determines the meaning of his life, the practice of ascesis necessary for the cause ofosis as the final goal of human personality, the parallels between the doctrine of passions and profound psychology. For philosophers, theologians, religion scholars, psychologists, culturologists and all those interested in the problems of philosophical and religious anthropology, psychology of religion, medieval Byzantine and Russian culture and Orthodox spirituality.