Aurelius Augustinius is another name for Augustine of Hippo, later canonized St. Augustine. He wrote his best-known work, The City of God, in the early Fifth Century. It's still one of the most influential works of Christian theology, but it's more than that. It's a history book, a savage polemic, and a treatise of moral philosophy. It's a long, dense book, but it rewards careful reading. You should check it out, and you should read the excellent study guide available on this website.

The fall of Rome to the Visigoths in the Fifth Century was a catastrophe for Christians. Rome was the seat of the Popes, the epicenter of their faith. Everyone called it The Eternal City, and this reinforced the notion that Christianity, too, was forever. The adoption of the faith into the Roman Empire made it seem invincible into the bargain. So, when the city was abandoned by the Imperium and sacked by Gothic armies, it seemed like Christianity, like Rome, was finished. Recriminations began while the rubble was still smoldering. Tradition-minded Romans blamed Christians, who now counted the Emperor among them, for abandoning ancient gods, bringing their wrath down on the city. Augustine, who was by now Bishop of Hippo, defended Christian doctrine and tried to persuade influential Church and Imperial figures to look elsewhere to explain the fall of Rome by publishing The City of God.

The book re-tells the history of the world as a struggle between good and evil forces, between the forces of light and darkness, between God and the Devil. It portrays Earthly and Heavenly cities, standing in for spiritual and temporal empires, and its central message is, "Don't worry, because the spiritual empire will win in the end." Augustine went to great lengths to shift the blame for Rome's decline away from Christianity. He went so far as to argue that, but for Christianity, the decline would have been swifter, and worse. Christianity, in other words, saved Rome from itself. This, and the idea that Christians should stop worrying about Earthly affairs, which were in the hand of the Devil, and focus only on Heavenly affairs, which were in the hand of God and were supposed to deflect the public's anger over the supposed betrayal of Rome by the baptized Emperor and citizens.