Augustine was consecrated as assistant Bishop by Valerius in 395 A.D. and became the actual Bishop of Hippo in 396 A.D. at the death of Valerius. He established common life in his residence and required his clergy to give up their property so as to live the early Christians ideal.
Augustine refuted the Manichians by teaching that God is good and that evil comes from the free decisions of men and angels.
During his episcopacy Augustine faced the Donatists, an heretical group of bishops of north Africa. The Donatists maintained that the Church was the assembly of the just and that the clergy who had in some way cooperated in the persecution and who had lost the grace of the Holy Spirit could not effectively administer the sacraments. Augustine maintained that the real power of the sacraments did not reside in the holiness of the individual but in the God's power at work through the ministers of the church and its sacraments. In the end, Augustine prevailed over the Donatists.
Another controversy in which Augustine became involved the was error of Pelagianism. Augustine taught that human beings born in Original Sin were incapable of saving themselves without the grace of God. Pelagius instead taught that Adam was just a bad example and not the father of sinful humanity. Pelagius saw salvation as merely the progress from bad behavior to good behavior by following Christ. This heresy was condemned by more Church Councils than any other heresy.
The third heresy which Augustine faced was Arianism. Arius, a priest of Egyptian Alexandria, taught that Christ was not equal to the Father. Christ was nothing more a creature more perfect than other creatures. Augustine argued that "whatever is spoken of God is spoken according to substance, then that which is said, 'I and the Father are one,' is spoken according to substance. Therefore there is one substance of the Father and the Son." (On the Trinity, Bk 5.3)
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