Damascene, St John: - One of the Fathers of the Eastern Orthodox Church, St. John Damascene is best known for what he did to protect icons. Because he wrote so much about the Assumption of Mary, the Catholic Church calls him a Doctor of the Church. He is also known as the Doctor of the Assumption. He was also a well-known proponent of the idea of perichoresis. He used it as an academic term to explain how the divine and human natures of Christ overlap and how the hypostases of the Trinity relate to each other. John's writing comes at the end of the Patristic time of dogmatic development. He doesn't add anything new to theology, but rather summarizes what had happened in the hundreds of years before him. He is called the "last of the Greek Fathers" in Catholic doctrine because of this. John was born in Damascus in 675 or 676 to a well-known Christian Arab family from Damascus. His dad, Sarjun ibn Mansur, was a worker for the early Umayyad Caliphate. In the time of Emperor Heraclius, his grandfather Mansur ibn Sarjun was a well-known Byzantine official in Damascus. He was in charge of the region's taxes and also worked for Emperor Maurice.