DANIEL J. SAHAS is a member of the Department of Religious Studies at the University of Waterloo, Waterloo, Ontario; the author of John of Damascus on Islam: The 'Heresy of the Ishmaelites' (Leiden, 1972) and of a number of articles on Byzantine-Muslim relations; and a member of the Executive Committee, and representative of the Greek Orthodox Diocese of Canada at the General Board, of the Canadian Council of Churches.