The Hesychast controversy was a theological dispute in the Byzantine Empire during the 14th century between supporters and opponents of Gregory Palamas. While not a primary driver of the Byzantine Civil War, it influenced and was influenced by the political forces in play during that war. The dispute concluded with the victory of the Palamists and the inclusion of Palamite doctrine as part of the dogma of the Eastern Orthodox Church as well as the canonization of Palamas.
About the year 1337, Hesychasm attracted the attention of a learned member of the Orthodox Church, Barlaam, a Calabrian monk who had come to Constantinople some seven years earlier. Reacting to criticisms of his theological writings that Gregory Palamas, an Athonite monk and exponent of hesychasm, had courteously communicated to him, Barlaam encountered Hesychasts and heard descriptions of their practices. Trained in Western Scholastic theology, Barlaam was scandalized by the descriptions that he heard and wrote several treatises ridiculing the practices. Barlaam took exception to, as heretical and blasphemous, the doctrine entertained by the Hesychasts as to the nature of the uncreated light, identical to that light which had been manifested to Jesus' disciples at the Transfiguration on Mount Tabor, the experience of which was said to be the goal of Hesychast practice. His informants said that this light was not of the divine essence but was contemplated as another hypostasis. Barlaam held this concept to be polytheistic, inasmuch as it postulated two eternal beings, a visible (immanent) and an invisible (transcendent) God.