Middle Ages

When barbarian tribes overran the Roman Empire at the end of the fifth century, the very existence of the church in the West was threatened. For the next several centuries, the church would confront paganism, heresy, invasions, rapidly changing political orders, and racial diversity, all of which threatened its survival and challenged it to find new ways of enacting its mission in the world. In this situation the church not only endured, but it prospered and evangelized vast new territories.

Although the structures of the empire had vanished in the West, an old Roman sense for order and structure remained alive in the church. Under the able leadership of Pope Gregory the Great in the sixth century, the papacy increasingly assumed direction of the church in the West. Able popes in Rome continued to direct the church through this period. They developed a theological rationale for the increasing power of the papacy and created a bureaucracy strong and supple enough to support their efforts to govern the church throughout the West. Order prevailed at the local level as well, as a parish system slowly developed under the aegis of cathedrals, monasteries, and local nobility.

Monasticism played an important role in other developments. Monasteries were often places for Christian worship, learning, social and economic development, and works of charity throughout this period.

Gregory the Great, other popes, monastic figures, and theological leaders of the early medieval period also helped to unite European Catholicism with a stable and easily accessible popular theology. Catholics in this era increasingly tended to see salvation as a reward granted by God in view of the accumulation of merit, and they regarded the church as possessing a treasury of this merit. Christians were increasingly taught in this era that the saints in heaven might intercede for them and help them toward salvation with their prayers. The veneration of relics and the pilgrimages were among other practices thought to help the faithful on their way toward salvation. Those who had not acquired sufficient merit at the time of death might do so in purgatory after death.

The Roman Empire was destroyed in the West, but survived in the East. Theologians in the East continued to pursue theological controversy after the Council of Chalcedon (451). A number of eastern churches did not, in fact, accept the decisions of the Council of Chalcedon (451) which taught that in the one person of Christ there were two natures, one human and one divine. Some churches preferred to speak of Christ as having one nature, although they fully affirmed both his divinity and humanity. These churches would become the Oriental Orthodox or monophysite churches. Later on in the early middle ages, the Orthodox churches of the East were agitated by a prolonged controversy over the proper use of icons. Eminent theologians of the era, including John of Damascus, spoke to this controversy. It concluded with a decision approving the veneration of icons, which are a vital element in eastern devotional life. Throughout this period monasticism in the East flourished as did the mystical theology associated with Simeon the New Theologian and others. These developments and other factors, including continuing debate over the place of the Holy Spirit in the Trinity and the filioque clause in the Nicene Creed, caused East and West to drift farther apart. An exchange of condemnations in the year 1054 is often considered the event that made the so-called Great Schism between East and West formal.

A formidable challenge to both eastern and western Christianity arose in the East with the rise of Islam under the prophet Muhammad and his successors in the caliphate. From the middle of the seventh through the early eighth centuries Muslim armies swept from the eastern Mediterranean, across north Africa, and through Spain. This placed ancient centers of Christianity under Muslim rule and reduced the eastern empire. It also brought Christianity into contact with Islamic intellectual life and deepened the division between the separated eastern and western portions of the church.

In the ninth century, Christians began to gather new energy in the West. The Frankish king Charlemagne created a large empire in the center of Europe and was crowned Holy Roman Emperor in 800. The Frankish church radiated learning and reform throughout the continent. By the ninth and tenth centuries, European theologians were again debating issues including the presence of Christ in the eucharist and predestination. In the eleventh century Anselm of Canterbury began a probing exploration of how faith might be supported by reason, an inquiry that would set the stage for later medieval developments. In the same century Europeans began the series of crusades to recapture the Holy Lands for Christian control. Meanwhile impulses toward the reform of doctrine and practice radiated from the monasteries associated with the monastic foundation at Cluny. In the same century Christians began the effort to retake Spain from Muslim control, beginning the so-called reconquista. Throughout this period, Christians were energetic in evangelism. They consistently converted the pagan tribes that had invaded Europe. Heretical Arian invaders were likewise converted to Catholicism. The Celtic churches of Ireland and Scotland were early bases for mission in this period and in the sixth century Pope Gregory the Great dispatched Augustine of Canterbury to England to evangelize its kingdoms and bring them into the orbit of Latin Christendom. Beginning in the ninth century Byzantine missionaries were sent to the Slavic peoples living north of the Orthodox Churches. Bulgaria and Serbia were evangelized in the ninth century and Russia was converted in the tenth. Denmark and Norway were forcibly converted in the tenth century. Sweden was declared Christian by its king in the eleventh century.

The late middle ages was a period of both vitality and decline. Theology, monasticism, the papacy, the arts, and popular piety all flourished as never before. At the same time, decadence and corruption dramatically weakened the church. By the end of this era, many voices throughout the church were calling for urgent reform.

Due in part to impulses from the Islamic world and its better-preserved knowledge of the works of Aristotle, theology in the West enjoyed a richly creative period in the twelfth and thirteenth centuries. Peter Abelard and Peter Lombard were among the luminaries of the era. These and other theologians worked in the newly founded universities of the era. In the thirteenth century Thomas Aquinas brought western theology to a high point when he attempted to synthesize faith and reason in a new way. Other theologians of the Augustinian tradition continued to develop theological traditions associated with Augustine of Hippo. Still others, the so-called Latin Averroists, were more strongly attracted by the newly reintroduced philosophy of Aristotle as a basis for theological inquiry. Later theological developments included the appearance of the nominalist school which emphasized the omnipotence of God and contingency of historical patterns. Nominalism resulted in some instances in an extreme ecclesiastical authoritarianism while in other instances it could lead toward calls for reform.

Eastern theology in this period was often absorbed with matters relating to the devotional life and mystical traditions. One of the leading theologians of the era was Gregory Palamas who, for example, wrote in defense of the monastic practice of prayer known as hesychasm. Gregory and other theologians wrote widely on other topics as well.

In the West the popes of this period, including Innocent III, often made extreme claims for their authority over both church and state. By the end of the middle ages, however, it was clear that the popes were without control over either church or princes. In the fourteenth century the popes resided at Avignon and were under the direct control of French monarchs. This became known as the Babylonian Captivity of the church and scandalized the faithful. Later, during the so-called Great Schism, there emerged several rival popes, each claiming to be the successor of Peter. Throughout this period, the church acquired great wealth and an appetite for even more. This led to abuses including pluralism, absenteeism, and simony, all related to the buying and selling of offices in the church. Meanwhile clergy and monks regularly gathered money from believers through the sale of privileges associated with the repetition of masses, pilgrimages, relics, and indulgences.

Throughout this period there were calls for reform. In the thirteenth century monastic reformers created new orders, the so-called mendicant orders, pledged to the ideal of apostolic poverty. This was a direct challenge to the wealth of the church and its corrupting effects. Francis of Assisi formed the Franciscans with the intention of practicing poverty and evangelism. Dominic de Guzman founded the Dominicans as another mendicant order. It became known not only for its asceticism, but for its care for the church's orthodoxy. In the fourteenth and fifteenth centuries John Wycliffe in England and the Czech John Huss called for both theological and practical reform of the church. Others looked to the councils of the church to undertake the cause of reform.

By the end of the fifteenth century, it was apparent that neither individuals nor the conciliar movement had succeeded in reforming the church. To this distress was added the collapse of the Byzantine Empire in the East in 1453. This placed the Orthodox churches under the domination of Muslim overlords. As the century closed, calls for reform and renewal grew ever more urgent.