Nestorianism in the context of "Hebrew Roots"

Cyril of Alexandria (Ancient Greek: Κύριλλος Ἀλεξανδρείας; Coptic: Ⲡⲁⲡⲁ Ⲕⲩⲣⲓⲗⲗⲟⲩ ⲁ̅ or Coptic: Ⲡⲓⲁⲅⲓⲟⲥ Ⲁⲃⲃⲁ Ⲕⲩⲣⲓⲗⲗⲟⲥ ⲡⲓⲥⲧⲩⲗⲗⲟⲥ ⲛ̀ⲧⲉ ⲡⲓⲛⲁϩϯ or ⲡⲓ̀ⲁⲅⲓⲟⲥ Ⲕⲓⲣⲓⲗⲗⲟⲥ; c. 376–444) was the Patriarch of Alexandria from 412 to 444. He was enthroned when the city was at the height of its influence and power within the Roman Empire. Cyril wrote extensively and was a major player in the Christological controversies of the late 4th and 5th centuries. He was a central figure in the Council of Ephesus in 431, which led to the deposition of Nestorius as Patriarch of Constantinople.

Cyril is counted among the Church Fathers and also as a Doctor of the Church, and his reputation within the Christian world has resulted in his titles Pillar of Faith and Seal of all the Fathers. The Nestorian bishops at their synod at the Council of Ephesus declared him a heretic, labelling him as a "monster, born and educated for the destruction of the church".

Theodosius II (Ancient Greek: Θεοδόσιος Theodosios; 10 April 401 – 28 July 450), called "the Calligrapher", was Roman emperor from 402 to 450. He was proclaimed Augustus as an infant and ruled as the Eastern Empire's sole emperor after the death of his father Arcadius in 408. His reign was marked by the promulgation of the Theodosian law code and the construction of the Theodosian walls of Constantinople. He also presided over the outbreak of two great Christological controversies, Nestorianism and Eutychianism.

In the year before the First Council of Constantinople in 381, Nicene Christianity became the official religion of the Roman Empire when Theodosius I, emperor of the East, Gratian, emperor of the West, and Gratian's junior co-ruler Valentinian II issued the Edict of Thessalonica in 380, which recognized the catholic orthodoxy, as defined by the Council of Nicea, as the Roman Empire's state religion. Historians refer to this state-sponsored church using a variety of terms: the catholic church, the orthodox church, the imperial church, the Roman church, or the Byzantine church, with some also used for wider communions extending beyond the Roman Empire. The Eastern Orthodox Church, Oriental Orthodoxy, and the Catholic Church all claim to stand in continuity from the Nicene Christian church to which Theodosius granted recognition. Political differences between the Eastern Roman Empire and the Persian Sassanid Empire led to the separation of the Church of the East in 424. A doctrinal split within the imperial church led to the independence of early Oriental Orthodoxy, while the fall of the Western Roman Empire initiated the gradual separation between Eastern and Western Christianity, culminating in the East-West schism of 1054. The Western Church evolved into the Latin Catholic Church while the Eastern Church that remained under the patronage of the Eastern empire and evolved into the Greek Orthodox Church.

Earlier in the 4th century, following the Diocletianic Persecution of 303–313 and the Donatist controversy that arose in consequence, Constantine the Great had convened councils of bishops to define the orthodoxy of the Christian faith and to expand on earlier Christian councils. A series of ecumenical councils convened by successive Roman emperors met during the 4th and the 5th centuries, but Christianity continued to suffer rifts and schisms surrounding the theological and christological doctrines of Arianism, Nestorianism, Miaphysitism, and Dyophysitism. In the 5th century, the Western Roman Empire decayed as a polity; invaders sacked Rome in 410 and in 455, and Odoacer, an Arian barbarian warlord, forced Romulus Augustus, the last nominal Western Emperor, to abdicate in 476. However, apart from the aforementioned schisms, the church as an institution persisted in communion, if not without tension, between the East and West. In the 6th century, the Byzantine armies of the Byzantine Emperor Justinian I recovered Italy and other regions of the Western Mediterranean shore. The Byzantine Empire soon lost most of these gains, but it held Rome, as part of the Exarchate of Ravenna, until 751, a period known in church history as the Byzantine Papacy. The early Muslim conquests of the 7th–9th centuries would begin a process of converting most of the then-Christian world in the Levant, Middle East, North Africa, regions of Southern Italy and the Iberian Peninsula to Islam, severely restricting the reach both of the Byzantine Empire and of its church. Christian missionary activity directed from the capital of Constantinople did not lead to a lasting expansion of the formal link between the church and the Byzantine emperor, since areas outside the Byzantine Empire's political and military control set up their own distinct churches, as in the case of Bulgaria in 919.

The Chalcedonian schism, also known as the Monophysite schism, is the break of communion between the Oriental Orthodox Churches and the Great Church (which later became the Eastern Orthodox Church and Catholic Church) in the aftermath of the Council of Chalcedon. Although the bishops at Chalcedon greatly respected Cyril of Alexandria and used his writings as a benchmark for orthodoxy, opponents of the council believed that the Chalcedonian Definition, which states that Christ is "acknowledged in Two Natures", was too close to Nestorianism and contradicts Cyril's formula "one nature of God the Word incarnate". The Council had also deposed the Pope of Alexandria, Dioscorus, but his supporters continued to consider him their rightful Pope, refusing to recognise the council-appointed Proterius.

The anti-Chalcedonian strongholds were in Egypt, Palestine and later Syria. Over the next century, their communities gradually separated from the official church of the Byzantine Empire, eventually becoming the Oriental Orthodox Churches. The imperial government made many attempts to mend the schism, generally by trying to compromise between the two positions, but these attempts only created further heresies and schisms. The Arab conquests of the Levant and of Egypt in the 7th century fossilised the schism, but ecumenical dialogue between Chalcedonian and non-Chalcedonian Christians has been renewed since the 20th century.

The Council of Chalcedon (/kælˈsiːdən, ˈkælsɪdɒn/; Latin: Concilium Chalcedonense) was the fourth ecumenical council of the Christian Church. It was convoked by the Roman emperor Marcian. The council convened in the city of Chalcedon, Bithynia (modern-day Kadıköy, Istanbul, Turkey) from 8 October to 1 November 451. The council was attended by over 520 bishops or their representatives, making it the largest and best-documented of the first seven ecumenical councils. The principal purpose of the council was to re-assert the teachings of the ecumenical Council of Ephesus against the teachings of Eutyches and Nestorius. Such doctrines viewed Christ's divine and human natures as separate and distinct (Nestorianism), or viewed Christ as solely divine (monophysitism). The Council of Chalcedon issued the Chalcedonian Definition, stating that Jesus is "perfect both in deity and in humanness; this selfsame one is also actually God and actually man." The Council's judgments and definitions regarding the divine marked a significant turning point in the Christological debates.

In the 5th century in Christianity, there were many developments which led to further fracturing of the State church of the Roman Empire. Emperor Theodosius II called two synods in Ephesus, one in 431 and one in 449, that addressed the teachings of Patriarch of Constantinople Nestorius and similar teachings. Nestorius had taught that Christ's divine and human nature were distinct persons, and hence Mary was the mother of Christ but not the mother of God. The Council rejected Nestorius' view causing many churches, centered on the School of Edessa, to a Nestorian break with the imperial church. Persecuted within the Roman Empire, many Nestorians fled to Persia and joined the Sassanid Church (the future Church of the East) thereby making it a center of Nestorianism. By the end of the 5th century, the global Christian population was estimated at 10-11 million. In 451 the Council of Chalcedon was held to clarify the issue further. The council ultimately stated that Christ's divine and human nature were separate but both part of a single entity, a viewpoint rejected by many churches who called themselves miaphysites. The resulting schism created a communion of churches, including the Armenian, Syrian, and Egyptian churches, that is today known as Oriental Orthodoxy. In spite of these schisms, however, the imperial church still came to represent the majority of Christians within the Roman Empire.

At the end of the 4th century the Roman Empire had effectively split into two states although its economy and the Church were still strongly tied. The two halves of the empire had always had cultural differences, in particular exemplified by the widespread use of the Greek language in the Eastern Empire and the more limited use of Greek in the West (Greek was used in the West but Latin was displacing it as the spoken vernacular. By the 5th century scholars in the West had begun to abandon Greek in favor of the use of Latin. The Church in Rome, in particular, began to encourage the use of Latin in the western provinces and published Jerome's Vulgate, the first authorized translation of the Bible in Latin.

Christotokos (Greek: Χριστοτόκος) is a title of Mary, the mother of Jesus. Its English translation is Christ-bearer or, less literally, Mother of Christ. It is used by Christians universally, but particular attention is given to it in the non-Ephesian (or so-called "Nestorian") Church of the East, due to its grievances with the title Theotokos.

Dyophysitism (/daɪˈɒfɪsaɪtɪzəm/; from Greek δύο dyo, "two" and φύσις physis, "nature") is the Christological position that Jesus Christ is in two distinct, inseparable natures: divine and human. It is accepted by the majority of Christian denominations, including the Catholic Church, Eastern Orthodox Church, Church of the East, Anglicanism, Methodism, Reformed Christianity and Lutheranism. It is rejected by the Oriental Orthodox churches, who hold to Miaphysitism—that Jesus Christ is of two natures united into one composite nature—while rejecting Monophysitism as heresy along with other extant denominations.

Those who subscribe to the "two natures after the union" formula on either Chalcedonian and Nestorian side were referred to as dyophysites (/daɪˈɒfəsaɪts/). It is related to the doctrine of the hypostatic union and prosopic union.

Terms for Syriac Christians are endonymic (native) and exonymic (foreign) terms, that are used as designations for Syriac Christians, as adherents of Syriac Christianity. In its widest scope, Syriac Christianity encompass all Christian denominations that follow East Syriac Rite or West Syriac Rite, and thus use Classical Syriac as their main liturgical language. Traditional divisions among Syriac Christians along denominational lines are reflected in the use of various theological and ecclesiological designations, both historical and modern. Specific terms such as: Jacobites, Saint Thomas Syrian Christians, Maronites, Melkites, Nasranis, and Nestorians have been used in reference to distinctive groups and branches of Eastern Christianity, including those of Syriac liturgical and linguistic traditions. Some of those terms are polysemic, and their uses (both historical and modern) have been a subject of terminological disputes between different communities, and also among scholars.

Territorially, Syriac Christians are divided in two principal groups: Syriac Christians of the Near East, and Syriac Christians of India. Terminology related to Syriac Christians of the Near East includes a specific group of ethnoreligious terms, related to various Semitic communities of Neo-Aramaic-speaking Christians, that are indigenous to modern Syria, Iraq, Iran, Turkey, Lebanon, Israel, Jordan, and Palestine.