As Christianity spread within the Roman Empire and beyond, it developed a hierarchical organization, with patriarchs, bishops, and priests—all men—replacing the house churches of the early years, in which women played a more prominent part. At least in some places, however, women continued to exercise leadership and even priestly roles, prompting Pope Gelasius in 494 to speak out sharply against those who encouraged women “to officiate at the sacred altars, and to take part in all matters imputed to the offices of the male sex, to which they do not belong.”28 In general, though, the exclusion of women from the priesthood established a male-dominated clergy and a patriarchal church, which has lasted into the twenty-first century.

The emerging Christian movement was, however, anything but unified. Its immense geographic reach, accompanied by inevitable differences in language, culture, and political regime, ensured that a single focus for Christian belief and practice was difficult to achieve. Doctrinal differences also tore at the unity of Christianity and embroiled church authorities in frequent controversy about the nature of Jesus (was he human, divine, or both?), his relationship to God (equal or inferior?), and the always-perplexing concept of the Trinity (God as Father, Son, and Holy Spirit). There was debate as well about what writings belonged in the official New Testament, as dozens of letters, gospels, poems, and songs circulated among the early Christian communities. A series of church councils—at Nicaea (325 C.E.), Chalcedon (451 C.E.), and Constantinople (553 C.E.), for example—sought to define an orthodox, or correct, position on these and other issues, declaring those who disagreed as anathema and expelling them from the Church. Thus Egyptian Christians, for example, held to the unorthodox position called Monophysite. This view, that Jesus had a single divine nature simply occupying a human body, expressed resistance to domination from Rome or Constantinople, which held that Jesus was both fully human and fully divine. Likewise, the Church of the East adopted Nestorianism, another unorthodox view that emphasized the human side of Jesus’ nature and distinguished its theology from the Latin and Eastern Orthodox Churches.

Beyond these theological debates, political and cultural differences generated division even among the orthodox. The bishop of Rome gradually emerged as the dominant leader, or pope, of the Church in the western half of the empire, but his authority was sharply contested in the East. This division contributed to the later split between the Latin, or Roman Catholic, and the Greek, or Eastern Orthodox, branches of Christendom, a division that continues to the present (see Chapter 10). Thus the Christian world of 500 C.E. was not only geographically extensive but also politically and theologically very diverse and highly fragmented.

Buddhists too clashed over various interpretations of the Buddha’s teachings, and a series of councils failed to prevent the division between Theravada, Mahayana, and other approaches. A considerable proliferation of different sects, practices, teachings, and meditation techniques subsequently emerged within the Buddhist world, but these divisions generally lacked the “clear-cut distinction between ‘right’ and ‘wrong’ ideas” that characterized conflicts within the Christian world.29 Although Buddhist states and warrior classes (such as the famous samurai of Japan) sometimes engaged in warfare, religious differences among Buddhists seldom provided the basis for the bitterness and violence that often accompanied religious conflict within Christendom. Nor did Buddhists develop the kind of overall religious hierarchy that characterized Christianity, although communities of monks and nuns, organized in monasteries, created elaborate rules to govern their internal affairs.