Syriac Christianity is a branch of Eastern Christianity of which formative theological writings and traditional liturgies are expressed in the Classical Syriac language, a variation of the old Aramaic language. Along with Greek and Latin, Classical Syriac was one of the three most important languages of Early Christianity. It became a vessel for the development of a distinctive Syriac form of Christianity which flourished throughout the Near East and other parts of Asia during Late Antiquity and the Early Medieval period, giving rise to various liturgical and denominational traditions represented in modern times by several assemblies which continue to uphold the religious and cultural heritage of Syriac Christianity. The Syriac language is a variety of the Aramaic language that emerged in Edessa, Upper Mesopotamia in the first centuries AD. It is related to the Aramaic of Jesus, a Galilean dialect, a relationship that adds to its prestige for Christians. The ruins of the Dura-Europos church, dating from the first half of the 3rd century, are concrete evidence of the presence of organized Christian communities in the Aramaic-speaking area, far from Jerusalem and the Mediterranean coast. There are traditions of the preaching of Christianity in the region as early as the time of the Apostles. The fourth century is marked by the many writings in Syriac of Saint Ephrem the Syrian, the Demonstrations of the slightly older Aphrahat, and the anonymous ascetical Book of Steps. Syriac Christianity has become split into two liturgical traditions: the East Syriac Rite and the West Syriac Rite. The bishops who took part in the First Council of Nicaea in 325, the very first of the ecumenical councils, included twenty from Syria and one from Persia. Two councils held in the following century divided Syriac Christianity into two opposing parties. In 431, the Council of Ephesus, the third ecumenical council, condemned Nestorius and Nestorianism. This condemnation was subsequently ignored by the East Syriac Church of the East. Even in its modern form, the Assyrian Church of the East and Ancient Church of the East continues to honor Nestorius as a teacher and a saint. In 451, the Council of Chalcedon, the fourth ecumenical council, condemned Monophysitism and also rejected Dyoprosopism. This council was rejected by the Oriental Orthodox Churches, including the Syriac Orthodox Church, which uses the West Syriac Rite. The Patriarchate of Antioch was consequently divided between two communities, pro-Chalcedonian and non-Chalcedonian. The Chalcedonians were often labelled "Melkites" (Imperials), while their opponents were labelled Monophysites (those who believe in the one, rather than two natures of Christ) and Jacobites (after Jacob Baradaeus). In 553, the Council of Constantinople, the fifth ecumenical council, anathematized Theodore of Mopsuestia and also condemned several writings of Theodoret of Cyrus and Ibas of Edessa. Because those three theologians were highly regarded among Eastern Syriac Christians, further rifts were created. Theological estrangement between East Syriac and West Syriac branches became manifested as a prolonged rivalry that was particularly acrimonious between the Church of the East and the Maphrianate of the East (Syriac Orthodox Church). Each branch claimed that its doctrines were not heretical and accused the other of teaching heresy. This estrangement persisted through the medieval and early modern periods and into the present era.