The conversion of the emperor Constantine in 313 was a turning point in the history of the Church. From being the faith of a persecuted minority, Christianity became the official religion of the Roman Empire. This book describes the consequences of this development - "Caesaropapism" where by emperors sought to control the Church, the development of Christian architecture and liturgy and the growth of theological thought in the writings of the Fathers of East and West. It shows how, scarcely a century after Constantine, the Church survived the collapse of the Empire, becoming the guardian of culture and civilization in a wilderness of barbarian kingdoms that stretched from Britain to the Near East where Islam, in the sixth century, destroyed the Churches of Syria, Egypt and North Africa. With the advent of Charlemagne, civilization and order were again restored during the eighth and ninth centuries until anarchy returned in the tenth and the West was once more in travail bringing to birth a new world which was to be mediaeval Christendom.