The Christian church was a defining element in medieval society. There were others, of course, but the Middle Ages without the church would not be the historic Middle Ages. It was the one international ingredient which bound together disparate peoples in a shared faith and ritual and by a common learned language. Variations there indeed were, but the same Creed was recited at the same kinds of liturgical ceremonies from Iceland to Sicily and in tens of thousands of villages throughout Western Europe. The general councils of the church drew members to Lyons, Rome, Vienne, Constance and elsewhere in the only truly international assemblies of the Middle Ages. Theologians and canon lawyers not only spoke the same Latin language, but they discussed the same issues. The existence of local customs and traditions added to the flavour of the religious culture of the times and also served to emphasize the overarching transcendence of the medieval church.
The underlying assumptions about the nature and purpose of life were common currency. A triune God exists and is involved in human affairs. Christ is God and man, who came to earth to redeem the human race. Life on earth is a pilgrimage to another life, where the obvious injustices of this life will be redressed in eternal bliss or eternal punishment. Even Christians who diverted from traditional Christianity—and who were labelled heretics—generally shared the same basic world-view. Scepticism and disbelief, on the evidence, were extremely rare but not totally absent. Yet it was the religious assumptions of society generally, whether questioned or unquestioned, that helped to define the age.
If the medieval church can be said to have a body and a soul, then the external institution pertains to the body and the inner spiritual life of Christian people pertains to the soul. A history of the church cannot limit itself to the institution nor, on the other hand, should it omit the institution or treat it almost incidentally. History records how an institution, which was believed to have been divinely founded, was ruled by human beings, who were not divine, sometimes far from being even spiritual. This institution grew and, as it grew, required organization and rules. From the time that we might want to use the word medieval, perhaps from the sixth century, we can see a network of bishops with one, at Rome,