Papacy and empire
Conflict with the East was both a cause and an effect of the distinctive development of Western Christianity during the Middle Ages. If popes Leo I and Gregory I may be styled the architects of the medieval papacy, popes Gregory VII (reigned 1073–85) and Innocent III (reigned 1198–1216) should be called its master builders. Gregory VII reformed both the church and the papacy from within, establishing the canonical and moral authority of the papal office when it was threatened by corruption and attack; in the pontificate of Innocent III the papal claims to universality reached their zenith at all levels of the life of the church. Significantly, both these popes were obliged to defend the papacy against the Holy Roman emperor and other temporal rulers. The battle between the church and the empire is a persistent theme in the history of medieval Christianity. Both the involvement of the church in secular affairs and the participation of temporal rulers in the Crusades can be read as variations on this theme. Preoccupied as they usually are with the history of the church as an institution and with the life and thought of the leaders of the church, the documentary sources of knowledge about medieval Christianity make it difficult for the social historian to descry “the religion of the common man” during this period. Both the “age of faith” depicted by neo-Gothic Romanticism and the “Dark Ages” depicted by secularist and Protestant polemics are gross oversimplifications of history. Faith there was during the Middle Ages, and intellectual darkness and superstition too; but only that historical judgment of medieval Christianity is valid that discerns how subtly faith and superstition can be blended in human piety and thought.