He obtained a teaching position in Milan in northern Italy, where he met two things that profoundly influenced him. One was the preaching of the bishop, St. Ambrose. Another was his discovery of neo-Platonist philosophy through the writings of Plotinus.
His final conversion to a holier Christian life was dramatic. He had been talking to a friend, when all of a sudden he was filled with remorse for his sinful life. He could not restrain his tears, so he left his friend to be by himself in the garden, where he gave free rein to his weeping. He begged God to pardon his past life. Suddenly he heard as if coming from a neighbors house a voice like that of a little boy or little girl singing repeatedly "Take and Read" (et ecce audio vocem de vicina domo cum cantu dicentis et crebro repetentis, quasi pueri aut puellae, nescio, Tolle lege, tolle lege Confessions, VIII.12)
He went back to the house, snatched the book he was reading (the Epistles of St. Paul), opened it at random and read the first passage he saw. It was from the Letter to the Romans:
Let us live honorably as in daylight, not in orgies and drunkenness, not in debauchery and licentiousness, not in quarreling and jealousy. Instead put on the Lord Jesus Christ, and make no provision for the desires of the flesh. (Rom. 13.13)
He and his friend and his son Adeodatus were baptized by St. Ambrose. Eventually he returned to Africa and (while still a layman) he founded a monastery. His life was so exemplary that when the local Christians needed a priest, they voted unanimously for him and he was ordained priest. It was in similar circumstances that he became a bishop. (In those days bishops were chosen by the local church.)
During all this time he was writing books and letters. The list of his writings occupies several pages in an encyclopedia. It was by these writings that he became so influential both in his own time and in all the centuries afterwards. Not everyone agrees with Augustines ideas, but the vigor and originality of his thinking stimulated Christian debate.
His chief contributions to that debate were in four areas. First, his teaching on the Trinity. Second, his Christology which anticipates the doctrines of the Councils of Ephesus and Chalcedon. Third, his Ecclesiology. Fourth, his most controversial thinking was on the relationship between the grace of God and human freedom. Involved in that are the doctrines of original sin, salvation, and predestination.
Here in the Philippines the influence of St. Augustine has been very strong brought to us mainly by four religious groups that follow the Augustinian rule: the Augustinian friars (OSA), the Augustinian Recollect friars (OAR), the Augustinian nuns of La Consolacion, and the Augustinian Recollect nuns of Santa Rita de Casia.
To them on the feast of St. Augustine, our cordial greetings.