On August 24, 410 A.D., the Visigoths, led by Alaric, sacked Rome. For the people of late antiquity, August 24 was even more traumatic than September 11 was for us. Rome, the capital of the greatest empire the world had ever known, was plundered by barbarians, people Rome regarded as uncouth and inferior. In North Africa, these events prompted a Christian bishop to start writing about the lessons Christians should take away from the destruction of Rome. The result was a book that is every bit as relevant for our day as it was for his: The City of God...