Answer: Ambrose of Milan (AD 339–397), also called St. Ambrose, was the first early church father to be born into a Roman Christian family. He is best remembered for his successful fight against Arianism, his contributions to church music, his stance on the separation of church and state, and his mentorship of the church father Augustine. Long after his death, Ambrose would be named a “doctor of the church” in the Catholic Church along with others such as Augustine, Pope Gregory, and Jerome.

Ambrose was born shortly after the First Council of Nicea into a wealthy and powerful Roman family. He became the governor of northern Italian provinces and was summoned to settle a conflict between rival religious factions: orthodox Catholics and Arians. Ambrose supported the Nicene Creed and had spoken against Arian theology. However, he was so well respected by both sides of the conflict that they demanded he become their bishop.

Ambrose’s experience in politics served him well in his role as bishop. Among his most distinctive teachings was his perspective on the relationship between church and state. Contrary to many of his peers, Ambrose held that the church was not morally subject to the ruling government. Rather, he taught, the government was subject to the moral authority of the church. Ambrose went so far as to ban the ruling emperor, Theodosius, from communion unless he repented of his role in a massacre of civilians.

This sense of political independence extended to Ambrose’s views of church matters, as well. While he agreed that Rome was the “spiritual” head of the universal church, he did not support the idea of Rome being the legal or governmental authority over all Christians.

Ambrose made several long-lasting contributions to Western Christianity. Among these are the first known book on Christian ethics—On the Duties of the Church’s Servants—as well as a massive library of writings, including the anti-Arian works On the Faith and On the Holy Spirit. His mastery of Greek allowed him to analyze previous theologians with considerable depth. Ambrose is also credited with introducing the concept of congregational singing, which at the time was somewhat controversial.

By all accounts, Ambrose was an excellent preacher. One of his sermon quotes has entered modern parlance as an idiom: “When you are at Rome, live in the Roman style,” usually quoted as “When in Rome, do as the Romans do.” In his sermons, Ambrose of Milan greatly emphasized the role of the Holy Spirit in the life of each believer, along with a rejection of legalism and a clear support for personal faith. Interestingly, while he opposed excessive legalism, Ambrose encouraged asceticism—an austere, self-denying lifestyle. His work attracted the attention of a young Christian named Augustine, who would later be baptized by Ambrose and surpass him as a great figure in early Christian history.

Both the Roman Catholic Church and the Eastern Orthodox Church venerate Ambrose as a saint, commemorating him on December 7 of each year.