Augustine of Hippo ( 354-430 AD) "...was born in...Tagaste to a Christian mother and a Pagan father, raised in Roman north Africa, educated in Carthage, and employed as a professor of rhetoric in Milan by 383. He followed the Manichaean religion in his student days, and was converted to Christianity by the preaching and example of Ambrose of Milan. He was baptized at Easter in 387, and returned to north Africa and created a monastic foundation at Tagaste for himself and a group of friends. In 391 he was ordained a priest in Hippo Regius, (now Annaba, in Algeria). He became a famous preacher (more than 350 preserved sermons are believed to be authentic), and was noted for combating the Manichaean heresy.

In 396 he was made coadjutor bishop of Hippo (assistant with the right of succession on the death of the current bishop), and remained as bishop in Hippo until his death in 430. He left his monastery, but continued to lead a monastic life in the episcopal residence. He left a Rule (Latin, Regula) for his monastery that has led him to be designated the "patron saint of Regular Clergy," that is, parish clergy who live by a monastic rule.

Augustine died on August 28, 430, during the siege of Hippo by the Vandals. He is said to have encouraged its citizens to resist the attacks, primarily on the grounds that the Vandals adhered to Arian Christianity, which Augustine regarded as heretical....

...Augustine remains a central figure, both within Christianity and in the history of Western thought. Himself much influenced by Platonism and neo-Platonism, particularly by Plotinus, Augustine was important to the "baptism" of Greek thought and its entrance into the Christian, and subsequently the European intellectual tradition. Also important was his early and influential writing on the human will, a central topic in ethics, and one which became a focus for later philosophers such as Schopenhauer and Nietzsche. It is largely due to Augustine's influence that Western Christianity subscribes to the doctrine of original sin, and the Roman Catholic Church holds that baptisms and ordinations done outside of the Roman Catholic Church can be valid (the Roman Catholic Church recognizes ordinations done in Eastern Orthodox and Oriental Orthodox churches, but not in Protestant churches, and recognizes baptisms done in nearly all Christian churches). Catholic theologians generally subscribe to Augustine's belief that God exists outside of time in the "eternal present"; time existing only within the created universe.

Augustine's writings helped formulate the theory of the just war....

...St. Thomas Aquinas took much from Augustine's theology while creating his own unique synthesis of Greek and Christian thought....

...Augustine was canonized by popular recognition and recognized as a Doctor of the Church in 1303 by Pope Boniface VIII.... (from Wikipedia.com)