Trained in Western scholastic theology, Barlaam was scandalised by Hesychasm and began to combat it both orally and in his writings. As a private teacher of theology in the Western Scholastic mode, Barlaam propounded a more intellectual and propositional approach to the knowledge of God than the Hesychasts taught. Barlaam took exception to, as heretical and blasphemous, the doctrine entertained by the Hesychasts as to the nature of the uncreated light, the experience of which was said to be the goal of Hesychast practice. It was maintained by the Hesychasts to be of divine origin and to be identical to that light which had been manifested to Jesus' disciples on Mount Tabor at the Transfiguration. This Barlaam held to be polytheistic, inasmuch as it postulated two eternal substances, a visible (immanent) and an invisible God (transcendent).