A new emperor, Basil the Macedonian, reinstated Ignatius, and in 869 Nicholas’s successor, Adrian II (reigned 867–872), condemned Photius and sent legates to Constantinople to extort submission to papal supremacy from the Greeks. The Greeks resented the papal demands, and, when Ignatius died in 877, Photius quietly became patriarch again. Rome (at that moment needing Byzantine military support against Muslims in Sicily and southern Italy) reluctantly agreed to recognize Photius but on the condition of an apology and of the withdrawal of Greek missions to the Bulgars. Photius acknowledged Rome as the first see of Christendom, discreetly said nothing explicitly against the Filioque clause, and agreed to the provision that the Bulgars could be put under Roman jurisdiction provided that Greek missions were allowed to continue.
The main issue in the Photian schism was whether Rome possessed monarchical power of jurisdiction over all churches (as Nicholas and Adrian held), or whether Rome was the senior of five semi-independent patriarchates (as Photius and the Greeks thought) and therefore could not canonically interfere with the internal affairs of another patriarchate. The great East-West schism
The mutual distrust shown in the time of Photius erupted again in the middle of the 11th century after papal enforcement of Latin customs upon Greeks in southern Italy. The patriarch of Constantinople, Michael Cerularius, closed Latin churches in Constantinople as a reprisal. Cardinal Humbert came from Italy to protest, was accorded an icy reception, and left a bull of excommunication (July 16, 1054) on the altar of the great church of Hagia Sophia. The bull anathematized (condemned) Michael Cerularius, the Greek doctrine of the Holy Spirit, the marriage of Greek priests, and the Greek use of leavened bread for the Eucharist.
At the time, the breach was treated as a minor storm in which both sides had behaved with some arrogance. As Greeks and Latins became more estranged, however, people looked back on the events of 1054 as the moment of the final breach between East and West. (Not until December 7, 1965, were the mutual excommunications of 1054 abolished, by Pope Paul VI and the ecumenical patriarch Athenagoras I.) Henry Chadwick The Editors of Encyclopaedia Britannica From the schism to the Reformation
A major factor in the consolidation and expansion of Christianity in the West was the growth in the prestige and power of the bishop of Rome. The pope St. Leo I made the primacy of the Roman bishop explicit both in theory and in practice and must be counted as one of the most important figures in the history of the centralization of authority in the church. The next such figure was the pope St. Gregory I the Great, whose work shaped the worship, the thought, and the structure of the church as well as its temporal wealth and power. Although some of Gregory’s successors advocated papal primacy, it was the popes of the 11th century and thereafter who sought to exploit claims of papal authority over the church hierarchy and over all Christians.
Even while still a part of the universal church, Byzantine Christianity had become increasingly isolated from the West by difference of language, culture, politics, and religion and followed its own course in shaping its heritage. The Eastern churches never had so centralized a polity as did the church in the West but developed the principle of the administrative independence, or “autocephaly,” of each national church. During the centuries when Western culture was striving to domesticate the German tribes, Constantinople, probably the most civilized city in Christendom, blended classical and Christian elements with a refinement that expressed itself in philosophy, the arts, statecraft, jurisprudence, and scholarship. A thinker such as Michael Psellus in the 11th century, who worked in several of these fields, epitomizes this synthesis. It was from Byzantine rather than Roman missionaries that Christianity came to most of the Slavic peoples, including some who eventually sided with Rome rather than Constantinople (see also Eastern rite church). Byzantium was also the victim of Muslim aggressions throughout the period known in the West as the Middle Ages. Following the pattern established by the emperors Constantine and Justinian, the relation between church and state in the Byzantine empire coordinated the two in such a way as to sometimes subject the life and even the teaching of the church to the decisions of the temporal ruler—the phenomenon often, though imprecisely, termed caesaropapism.
All these differences between the Eastern and Western parts of the church, both the religious differences and those that were largely cultural or political, came together to cause the schism between the two. The break in 1054 was followed by further evidence of alienation—in the 13th century, in the sack of Constantinople by Western Christians in 1204 and the establishment of the Latin patriarchate there; and in the 15th century, after the failure of the union of Florence and after the fall of Constantinople to the Turks in 1453. 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 Leo I and Gregory I may be styled the architects of the medieval papacy, the popes St. 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, and 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 which discerns how subtly faith and superstition can be blended in human piety and thought is valid. Medieval thought
No product of medieval Christianity has been more influential in the centuries since the Middle Ages than medieval thought, particularly the philosophy and theology of Scholasticism, whose outstanding exponent was St. Thomas Aquinas (1224/25–1274). Scholastic theology was an effort to harmonize the doctrinal traditions inherited from the Fathers of the early church with the intellectual achievements of classical antiquity—in other words, to create a synthesis of faith and reason. Because many of the early Fathers both in the East and in the West had developed their theologies under the influence of Neoplatonism, the recovery of Aristotle—first through the influence of Aristotelian philosophers and theologians among the Muslims and eventually, with help from Byzantium, through translation and study of the authentic texts of Aristotle himself—caused a profound transformation in the methodology and substance of medieval thought. Because it combined fidelity to Scripture and tradition with a positive, though critical, attitude toward the “natural” mind, Scholasticism is a landmark both in the history of Christianity and in the history of Western culture and a symbol of the Christianization of society and culture. Reformation