Listers in one of the earliest polemics against Islam, the “superstition of the Ishmaelites” was viewed as a heresy of Christianity. In his work The Fount of Knowledge, St. John Damascene (c. 675 or 676 – 4 December 749) gifts the Church with one of the earliest summa theologicas. He is considered the last of the great Early Church Fathers and it would be difficult to exaggerate his influence on the Christian East. He is also esteemed in the Western Church as a forerunner to the scholastics and is considered by some as the first scholastic. St. John Damascene is best known for his fight against iconoclasm.1 The Fount of Knowledge is divided into three categories: “Philosophical Chapters” (Kephalaia philosophika) – “With the exception of the fifteen chapters that deal exclusively with logic, it has mostly to do with the ontology of Aristotle. It is largely a summary of the Categories of Aristotle with Porphyry’s “Isagoge” (Eisagoge eis tas kategorias). It seems to have been John Damascene’s purpose to give his readers only such philosophical knowledge as was necessary for understanding the subsequent parts of the “Fountain of Wisdom”. “Concerning Heresy” (Peri aipeseon) – “Little more than a copy of a similar work by Epiphanius, brought up to date by John Damascene. The author indeed expressly disclaims originality except in the chapters devoted to Islamism, Iconoclasm, and Aposchitae. To the list of eighty heresies that constitute the “Panarion” of Epiphanius, he added twenty heresies that had sprung up since his time. In treating of Islamism he vigorously assails the immoral practices of Mohammed and the corrupt teachings inserted in the Koran to legalize the delinquencies of the prophet.” “An Exact Exposition of the Orthodox Faith” (Ikdosis akribes tes orthodoxou pisteos) – “The third book of the “Fountain of Wisdom”, is the most important of John Damascene’s writings and one of the most notable works of Christian antiquity. Its authority has always been great among the theologians of the East and West. Here, again, the author modestly disavows any claim of originality — any purpose to essay a new exposition of doctrinal truth. He assigns himself the less pretentious task of collecting in a single work the opinions of the ancient writers scattered through many volumes, and of systematizing and connecting them in a logical whole.2 In his passage on Concerning Heresies, his section on the superstition of the Ishmaelites is considerably longer than most. One reason for this attention could be his prolonged battles against iconoclasm, in which the influence of Islam was a significant factor. The following are selected sections from his passage on Islam... https://www.stpeterslist.com/11698/...resy-8-quotes-from-st-john-damascene-a-d-749/ Afaik this has long been the position of the Orthodox and they maintain it to this day, i.e. that Islam began as an Arian-inspired cultus of personality of Mohammad. The Cucklic church long ago abandoned this position in the name of ecumenism but you'll still see a few here and there a few Protestants agreeing with John Damascene (the firebrand Pastor Anderson is one of the ones I've seen).