Theodore was a Greek-speaking monk of Tarsus — birthplace of St. Paul — educated in Greek classical and theological learning at Athens and Antioch, then a refugee from the Muslim conquest of Syria living in Rome. When Pope Vitalian was searching for a candidate to consecrate as Archbishop of Canterbury after the death of the previous appointee in plague, he chose Theodore — who was sixty-seven years old.
Theodore arrived in England in 669 and ruled the English Church for the next twenty-one years. He found a divided collection of small kingdoms with their own bishops, each loosely related to either Rome or Iona; he left a unified Church organized into a coherent diocesan and provincial structure, with regular synods, written records, settled boundaries, and standardized canon law. He effectively founded the English Church as an institution.
He summoned the great Synod of Hertford in 672 — the first national council of the English Church — which legislated comprehensively on Easter dating, monastic discipline, and episcopal authority. He founded the school of Canterbury, which under him and his African colleague Abbot Hadrian became the principal center of Greek and Latin learning in northern Europe; from it came the next generation of English scholarship including Bede.
He died at eighty-eight after a long and constructive episcopate; Bede ends his account: 'He was buried in the church of St. Peter; and his tomb may still be seen there with verses on it celebrating his birth and his works.'