Peter Brown, perhaps the greatest living authority on Mediterranean civilization in late antiquity, traces the growing power of Christian bishops as they wrested influence from philosophers, who had traditionally advised the rulers of Graeco-Roman society. In the new "Christian empire," the ancient bonds of citizen to citizen and of each city to its benefactors were replaced by a common Christianity and common loyalty to a distant, Christian autocrat. This transformation of the Roman empire from an ancient to a medieval society, he argues, is among the most far-reaching consequences of the rise of Christianity.