He was a Roman governor at Milan and a converted Christian, though not yet baptized, when he was elected bishop of Milan (374) and became a champion of orthodoxy. He was partly responsible for the conversion of St Augustine of Hippo. His knowledge of Greek enabled him to introduce much Eastern theology and liturgical practice into the West; Ambrosian (antiphonal) plainsong is associated with his name, and the Athanasian Creed has been attributed to him.