The purpose of this essay is to discuss the impact of Christianity on Medieval Europe, roughly between the years 325 and 1300. The emphasis will be on Christianity as a form of social organization, rather than as a belief system, although Christian beliefs certainly informed European society.
Christianity as a social organization began to make a major impact on European society in 325, when the Emperor Constantine called a council meeting of Christian bishops, since the decisions made at the meeting for the first time had the force of law. The bishops began to exercise some governmental functions in overseeing their congregations. In about 500 the Emperor Theodosius made Christianity the only legal religion, and turned over the property of all other religious groups (except for the Jews) to the Christian church. At about this same time, the western half of the empire was taken over by the German-speaking Goths, Visigoths, and Vandals, and despite some later attempts by the Eastern Empire to reconquer it, remained effectively independent thereafter.
Bishop Ambrose was able to assert independence of the Emperor in the east, and the Bishop of Rome remained the only Metropolitan bishop who was politically independent, and therefore came to be considered a resource for decisions about the welfare of the Christian church in general. The independence of the church meant that throughout the Middle Ages, Europe had in effect two parallel and independent governmental structures, the secular and the ecclesiastical, with different but complementary duties and privileges. As a result, Europe had a certain flexibility and resilience often lacking in monolithic systems. When one of the two systems happened not to be working well, the other could often take up the slack.
The Western church had an active missionary policy from the fourth century on, and gradually the peoples of Europe were baptized as Christians and even more gradually ...