[9]Whilst this judgment marked a significant turning point in the Christological debates,[10] it also generated heated disagreements between the council and the Oriental Orthodox Church, who did not agree with such conduct or proceedings.

[11] This disagreement would later inform the separation of the Oriental Orthodox Churches from the rest of Christianity, and led to the council being regarded as Chalcedon, the Ominous.

About two years after Cyril of Alexandria's death in 444, an aged monk from Constantinople named Eutyches began teaching a subtle variation on the traditional Christology in an attempt to stop what he saw as a new outbreak of Nestorianism.

Flavian preferred that the bishop and the archimandrite sort out their differences, but as his suggestion went unheeded, Eutyches was summoned to clarify his position regarding the nature of Christ.

Eventually Eutyches reluctantly appeared, but his position was considered to be theologically unsophisticated, and the synod finding his answers unresponsive condemned and exiled him.

Although it had been accidentally delayed, Leo wrote a compendious explanation of the whole doctrine involved, and sent it to Flavian as a formal and authoritative decision of the question.

Through the influence of the court official Chrysaphius, godson of Eutyches, in 449, the competing claims between the Patriarchs of Constantinople and Alexandria led Emperor Theodosius II to call a council which was held in Ephesus in 449,[19] with Dioscorus presiding.

The remainder of the Acts (the first session being wanting) are known through a Syriac translation by a Miaphysite monk, written in the year 535 and published from a manuscript in the British Museum.

The question before the council by order of the emperor was whether Flavian, in a synod held by him at Constantinople in November, 448, had justly deposed and excommunicated the Archimandrite Eutyches for refusing to admit two natures in Christ.

The papal legates refused to attend the second session at which several more orthodox bishops were deposed, including Ibas of Edessa, Irenaeus of Tyre, Domnus of Antioch, and Theodoret.

[23] Hilary, who later became pope and dedicated an oratory in the Lateran Basilica in thanks for his life,[24] managed to escape from Constantinople and brought news of the council to Leo who immediately dubbed it a "synod of robbers" – Latrocinium – and refused to accept its pronouncements.

The situation continued to deteriorate, with Leo demanding the convocation of a new council and Emperor Theodosius II refusing to budge, all the while appointing bishops in agreement with Dioscorus.

Pulcheria, the sister of Theodosius, may have influenced this decision, or even made the convention of a council a requirement during her negotiations with Aspar, the magister militum, to marry Marcian.

[citation needed] Leo had pressed for it to take place in Italy, but Emperor Marcian instead called for it to convene at Chalcedon, because it was closer to Constantinople, and would thus allow him to respond quickly to any events along the Danube, which was being raided by the Huns under Attila.

This time, Bishops Paschasinus of Lilybaeum and Julian of Cos and two priests Boniface and Basil represented the western church at the council.

According to the deacon Rusticus, there were in all sixteen sessions; this division is commonly accepted by scholars, including Karl Josef von Hefele, historian of the councils.

[citation needed] Marcian wished to bring proceedings to a speedy end, and asked the council to make a pronouncement on the doctrine of the Incarnation before continuing the trial.

"[33] The Oriental Orthodox contend that this latter teaching has been misunderstood as monophysitism, an appellation with which they strongly disagree but, nevertheless, refuse to accept the decrees of the council.

[37][b] The Confession of Chalcedon provides a clear statement on the two natures of Christ, human and divine:[41] We, then, following the holy Fathers, all with one consent, teach people to confess one and the same Son, our Lord Jesus Christ, the same perfect in Godhead and also perfect in manhood; truly God and truly man, of a reasonable [rational] soul and body; consubstantial [co-essential] with the Father according to the Godhead, and consubstantial with us according to the Manhood; in all things like unto us, without sin; begotten before all ages of the Father according to the Godhead, and in these latter days, for us and for our salvation, born of the Virgin Mary, the Mother of God, according to the Manhood; one and the same Christ, Son, Lord, only begotten, to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably; (ἐν δύο φύσεσιν ἀσυγχύτως, ἀτρέπτως, ἀδιαιρέτως, ἀχωρίστως – in duabus naturis inconfuse, immutabiliter, indivise, inseparabiliter) the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person (prosopon) and one Subsistence (hypostasis), not parted or divided into two persons, but one and the same Son, and only begotten God (μονογενῆ Θεόν), the Word, the Lord Jesus Christ; as the prophets from the beginning [have declared] concerning Him, and the Lord Jesus Christ Himself has taught us, and the Creed of the holy Fathers has handed down to us.The full text of the definition reaffirms the decisions of the Council of Ephesus and the pre-eminence of the Creed of Nicea (325).

[42][43] Initially, the council indicated their understanding that Pope Leo's ratification was necessary for the canon to be binding,[44] writing, "we have made still another enactment which we have deemed necessary for the maintenance of good order and discipline, and we are persuaded that your Holiness will approve and confirm our decree. ...

But we, wishing to gratify the pious Christian emperors, and the illustrious Senate, and the capital of the empire, have judged that an Ecumenical Council was the fittest occasion for effecting this measure.

"[45] Following Leo's rejection of the canon, Bishop Anatolius of Constantinople conceded, "Even so, the whole force of confirmation of the acts was reserved for the authority of Your Blessedness.

In a canon of disputed validity,[51] the Council of Chalcedon also elevated the See of Constantinople to a position "second in eminence and power to the Bishop of Rome".

In the early 5th century, this status was challenged by the bishops of Alexandria, but the Council of Chalcedon confirmed in Canon XXVIII: For the Fathers rightly granted privileges to the throne of old Rome, because it was the royal city.

[20]In making their case, the council fathers argued that tradition had accorded "honor" to the see of older Rome because it was the first imperial city.

[clarification needed] The bishops who were uneasy with the language of Pope Leo's Tome repudiated the council, saying that the acceptance of two physes was tantamount to Nestorianism.

This must be regarded[dubious – discuss] as the outward expression of the growing nationalist trends[citation needed] in that province against the gradual intensification of Byzantine imperialism, soon to reach its consummation during the reign of Emperor Justinian.

However, the Coptic Orthodox Church is miaphysite, which means they believe that Jesus Christ is both 100% human and 100% divine but in one person without mingling, confusion or alteration.

This led to the martyrdom, persecution and death of thousands[dubious – discuss] of Egyptian saints and bishops till the Arab Conquest of Egypt.

Although the theological differences are seen as limited (if non-existent), it is politics, the subsequent persecutions and the power struggles in the Roman Empire, that may have led to the Great Schism, or at least contributed significantly to amplifying it through the centuries.