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In the late fourth century, Christianity was established by Theodosius I as the state church of the Roman Empire. He further banned non-Christian public rituals. By the fifth century, the empire had split into eastern and western halves, with each part ruled by one of Theodosius’s sons. Constantinople was the capital of the Eastern Roman Empire (also called the Byzantine Empire), and Rome remained the capital of the Western Empire. The fragmentation of religious principles was as severe as the political divisions. Especially serious were the challenges to the established view of Christ’s divinity that rose associated with the teachings of Nestorius, Patriarch of Constantinople.
Rome’s Emperor Theodosius II convened two synods in 431 and 449, which were largely concerned with the implications of Nestorius’s assertions: the separation of the divine and human natures of Christ, which further implicated Mary’s status as his mother—that is, of the man but not the god. The council’s rejection of these ideas is largely responsible for the ensuing fragmentation, known as the Nestorian Break. In particular, churches associated with the Edessa school withdrew from the imperial church. Faced with persecution, many Nestorians fled to Persia. In 451, the Council of Chalcedon put forth the position that Christ was singular but contained both divine and human natures. In the Western Empire, Latin became the Church’s official language, leading to the publication of a Latin Bible.