St. John Damascene is a Doctor of the Church, and the last of the Greek Fathers. He’s also called John of Damascus.
He was born in Damascus, Syria, which was under Islamic domination, and succeeded his father as an advisor to the Caliph as chief representative of the Christian community. In 719, he was forced to resign because of his faith, and entered a monastery near Jerusalem, where he focused on prayer and writing.
He is the patron of pharmacists, icon painters and theology. His feast day is December 4.