A preacher, Pelagius found himself in Rome, and became concerned about the moral laxity of society he saw there. He blamed this laxity on the theology of divine grace preached by St Augustine of Hippo, among others. Pelagius was of the opinion that Augustine's teaching amounted to nothing short of introducing Manicheanism into Christianity. He accused Augustine of elevating evil to the same status as God and teaching pagan fatalism as if it were a Christian doctrine. While he is held up as the originator of the doctrine of Pelagianism, it can be argued that the monk may have never actually held that doctrine and has been subject to revision by his enemies.
When Alaric sacked Rome in 410, Pelagius fled to Carthage, where he came into further conflict with Augustine. His follower Coelestius was condemned by a church council there. Pelagius then fled to Jerusalem, but Augustine's followers were soon on his trail; Orosius went to Jerusalem to warn St Jerome against him.