In "On the Duties of the Clergy" St. Ambrose gives a detailed and definitive instruction on how the early leaders of the Church should behave and how they should lead their flock. An important read for all of those called to become spiritual leaders. Aurelius Ambrosius, better known in English as Saint Ambrose (c. 330 - 4 April 397), was an archbishop of Milan who became one of the most influential ecclesiastical figures of the 4th century. He was one of the four original doctors of the Church. He is patron saint of Milan.