The movement of large numbers of Christians from one place to another, as immigrants, pilgrims, monks, bishops and theologians, connected numerous local forms of Christianity across the Greek-speaking world. Churches and monasteries were built in urban and rural locations, to provide fixed points for the daily lives of Greek Christians. Of the numerous councils held circa 300-600, most were strictly regional or local. The majority were never recognised as ecumenical, though some could be regarded as trial runs in which significant positions and terms were aired. What should be remembered about the five councils in this era that eventually came to be recognised as ecumenical (Nicaea in 325; Constantinople in 381; Ephesus in 431; Chalcedon in 451; Constantinople in 553) is, first, that they were directly under the influence of emperors who wanted their wishes fulfilled. Second, the Christian leaders who attended these councils often wrangled at least as much over the ranking of their sees as over theological issues.

By Constantine's time in both east and west, the baptismal creed had been shaped to give affirmations which were simultaneously denials of gnostic heresy. The controversy about Origen's orthodoxy became acute again in the time of Justinian who, by decree, condemned Origen, Evagrius and Didymus. An accusation of heresy was brought before Aurelius, bishop of Carthage, at which, despite his eloquent protests that he was not denying the need for infants to be baptized, Celestius was declared excommunicate. He left for Ephesus. Augustine was moved to write by the sympathy which Celestius' theses evoked in Africa. The council of Ephesus inaugurated a series of ecumenical councils, and numerous colloquia and lesser councils, to try to reach agreement between the two main groups. The party of 'one nature', called by their opponents 'Monophysites', regarded the party of 'two natures' as holding Jesus to be no more than an inspired man.