Once again, Augustine presented the argument that won: Pelagius was officially condemned in 416 and sent into exile. But Pelagianism remained influential, and Augustine spent his final years locked in a long-distance debate with an intelligent and articulate advocate of Pelagianism, Julian of Eclanum. Among other matters, Augustine and Julian clashed on the nature of human sexuality. Augustine identified the beginning of sexual desire with the beginning of human disobedience, Adam and Eve's original sin that tainted all humankind. Julian, however, could not accept the idea of original sin. He insisted that sexual desire was simply another of the bodily senses, and that the justice of God would not inflict punishment on the entire human race for the disobedience of one person.
In his debates with the Pelagians, Augustine broached another difficult issue, that of predestination. Because Augustine had argued that only the grace of God could move human beings toward salvation, the issue of how God chose those who would be saved became paramount. Augustine asserted that only a few people were saved, and only God knew who was saved and who was not. This assertion provoked a sort of revolt among several French monastic communities during 428. If one could undertake heroic acts of self-denial and spiritual commitment, as the monks had done, but still not know if one was saved, then what was the point of trying? In response to letters from the monks, Augustine acknowledged that predestination was a difficult issue, but he refused to yield the point. Predestination did not mean that human beings could safely give up spiritual striving; perseverance in faith was one of God's gifts to human beings.
In 429, north Africa was invaded by the Vandals, another barbarian tribe from Europe. The Vandals besieged the city of Hippo during the summer of 430; Augustine fell ill during August. According to his biographer, Possidius, Augustine spent the last days of his life studying the penitential psalms, which he had posted on the walls of his room, and weeping over his sins. He demanded that no one visit him, giving him uninterrupted time to pray. Augustine died on August 28, 430, at the age of 75, so he did not live to see the Vandals overrun Hippo in 431. The world Augustine had known, the old Roman Empire that had educated him even while he deplored it, was genuinely coming to an end. Augustine had an enormously influential role in shaping the world that replaced it, the Christianized civilization of Medieval Europe.
