The eastern and western churches played different roles in spreading Christianity, depending on their historical, cultural, and theological contexts. Here is a brief summary of their roles:
- The eastern churches, also known as the Eastern Orthodox Church, developed in the eastern part of the Roman Empire, especially in Constantinople, the new capital founded by Emperor Constantine in 330 CE. The eastern churches maintained a close relationship with the imperial power, which sometimes led to conflicts over doctrinal and liturgical issues, such as the use of icons. The eastern churches also faced the challenge of the rise of Islam, which conquered most of their territories in the 7th and 8th centuries. The eastern churches spread Christianity mainly through the missionary work of monks, such as St. Cyril and St. Methodius, who evangelized the Slavic peoples in the 9th century. The eastern churches also preserved the ancient traditions and writings of the Greek-speaking Christian world, and developed a rich and diverse spirituality and theology.
- The western churches, also known as the Roman Catholic Church, developed in the western part of the Roman Empire, which collapsed in the 5th century CE. The western churches became more independent from the political power, and asserted the primacy of the pope of Rome as the supreme leader of the church. The western churches also faced the challenge of the barbarian invasions, which disrupted the social and cultural order of Europe. The western churches spread Christianity mainly through the establishment of monasteries, which became centers of learning, culture, and civilization in the medieval period. The western churches also initiated the crusades, which aimed to reclaim the Holy Land from the Muslims, and the inquisition, which aimed to combat heresy and dissent within the church. The western churches also fostered the development of scholasticism, a rational and systematic approach to theology and philosophy.
The eastern and western churches had a long history of mutual interaction and influence, but also of growing divergence and conflict. The most significant event that marked the final separation between them was the East-West Schism of 1054, when the pope and the patriarch of Constantinople excommunicated each other over doctrinal and jurisdictional disputes. The schism was not healed until 1965, when the pope and the patriarch lifted the mutual excommunications and expressed a desire for reconciliation. Since then, the eastern and western churches have engaged in ecumenical dialogue and cooperation, while also maintaining their distinctive identities and traditions.