On the Christian Faith, the Holy Trinity and the Two Natures of Jesus Christ by St Ambrose

Aurelius Ambrosius (c. 340–397), better known in English as Ambrose, an Archbishop of Milan, became one of the most influential ecclesiastical figures of the 4th century. He served as the Roman governor of Liguria and Emilia, headquartered in Milan, before popular acclamation propelled him into becoming Bishop of Milan in 374. Ambrose staunchly opposed Arianism. Western Christianity identified Ambrose as one of its four traditional Doctors of the Church, and as the patron saint of Milan. He had notable influence on Augustine of Hippo (354-430).