By Fr. Robert Slesinski. 266 pages. Semyon Frank was a mystic and a philosopher. His mysticism and philosophy—better described as a ‘mystical philosophy’ in the mode of his great inspiration, Nicholas of Cusa (1401-64)—are both focused on the experience of what I want to call ‘Being as Communion.’ Yet to understand this dual identity of Frank (mystic-philosopher) and the relationship of mysticism to philosophy in him one must understand two fundamental poles of his life and thought that at first seem unconnected: metaphysics and Orthodoxy.