This essay is unique in that it presents the mediaeval church not merely as a major proponent in the struggle for temporal power, but as an all-pervasive aspect of mediaeval life itself. The papacy was no more the church than the empire was feudalism. The church was Christendom and Christendom was the totality of European civilization. It was a way of life which had for its first purpose the worship of God and after that the civilization of man. Its members were the inhabitants of western Europe led and comforted by their parish priests, ruled-and according to chance-abused or protected by their lords and bishops, who together glimpsed only occasionally and from afar the passing might and splendor of emperors and popes. It is this church which Professor Baldwin has described with a skill and accuracy grounded in the most rigorous historical discipline and m a sympathy and understanding which can derive only from deep religious faith.