The currently existing type of dialogue ofWestern and Eastern cultures makes a philosophical exploration of Christianity and Islam compelling as they are fundamental monotheistic religions capable of ensuring the peaceful interaction of various ethnic cultures in the age of deepening secularization. The present analysis of the philosophical and epistemological teachings of the Greek Byzantine Church Fathers and the thinkers of classical Arab-Islamic culture aims at overcoming stereotypes regarding the opposition of Christianity and Islam that strongly permeate both scholarly theorizing and contemporary social discourses. The authors scrutinize the epistemological principles of the exoteric and esoteric knowledge of the Islamic Golden Age and the apophatic and cataphatic ways of attaining the knowledge of God in Early Christianity. Special attention is paid to the analysis of the concepts of personal mystical comprehension of God in Sufism (fanā') and in Christianity (Uncreated Light). © 2020 by the authors.