May have studied medicine as he seemed to have a greater knowledge of the subject than most people. Monk at Saint Catherine’s Monastery on Mount Sinai. Travelled to Damascus, Syria, and Alexandria, Egypt. Defended the faith in Chalcedon, urged Christians to keep their faith in the face of invading Muslims, and ministered to those who had been driven into exile for staying Christian. Abbot of Saint Catherine’s. Fought against many of the heresies of the day. Wrote on a number of theological topics; the versions that have survived suffer from much editing and additions through the years.