In the fourth and fifth centuries the Christian church fiercely debated the nature of Christ. At the Council of Ephesus, 431 A.D. a series of statements was voted to eliminate any ambiguity in the church's teaching on this vital subject. Early in the conference, a letter was read into the minutes:

"We have in our hands the letter of the most holy and most reverend archbishop Cyril, which he wrote to the most reverend Nestorius, filled with counsel and advice, on account of his aberration from the right faith. . . . The letter follows:

"To the most religious and beloved of God, fellow minister Nestorius, Cyril sends greeting in the Lord. . . .

"I urge you, as a brother in the Lord, to propose the word of teaching and the doctrine of the faith with all accuracy to the people, and to consider that the giving of scandal to one even of the least of those who believe in Christ, exposes a body to the unbearable indignation of God. . . . We shall do most excellently if we shall turn to the words of the holy Fathers, and are zealous to obey their commands, proving ourselves, whether we be in the faith according to that which is written, and conform our thoughts to their upright and irreprehensible teaching."

The letter goes on to spell out the Truth that Nestorius ought to teach. Then wanting to avoid any ambiguity, Cyril gives a list of twelve errors so dangerous that anyone who believes them deserves a curse. These "anathemas" included the following:

"If anyone shall not confess that the Word of God the Father is united hypostatically to flesh, and that with that flesh of his own, he is one only Christ both God and man at the same time: let him be anathema.

"If any one asserts that, at the union of the Logos with the flesh, the divine Essence moved from one place to another; or says that the flesh is capable of receiving the divine nature, and that it has been partially united with the flesh; or ascribes to the flesh, by reason of its reception of God, an extension to the infinite and boundless, and says that God and man are one and the same in nature; let him be anathema.

"If anyone shall after the [hypostatic] union divide the hypostases in the one Christ, joining them by that connection alone, which happens according to worthiness, or even authority and power, and not rather by a coming together which is made by natural union, let him be anathema.

"If any one says that Christ, who is also Emmanuel, is One, not [merely] in consequence of connection, but [also] in nature, and does not acknowledge the connection of the two natures, that of the Logos and of the assumed manhood, in one Son, as still continuing without mingling; let him be anathema."

Cyril ended his letter to "the most religious and beloved of God, fellow minister Nestorius," by writing, "These things, therefore, I now write unto you for the love of Christ, beseeching you as a brother, and testifying to you before Christ and the elect angels, that you would both think and teach these things with us, that the peace of the Churches may be preserved and the bond of concord and love continue unbroken amongst the Priests of God."

"All the bishops cried out together: Whoever does not anathematize Nestorius let him be anathema. Such an one the right faith anathematizes; such an one the holy Synod anathematizes. Whoever communicates with Nestorius let him be anathema! We anathematize all the apostles of Nestorius: we all anathematize Nestorius as a heretic: let all such as communicate with Nestorius be anathema, etc., etc."

From The Nicene And Post-nicene Fathers: Translations of The Writings of The Fathers. Philip Schaff, D.D., LL.D. and Henry Wace, D.D. editors. Vol. 14: The Seven Ecumenical Councils of the Undivided Church. On line version at Christian Classics Ethereal Library (ccel.org). Public domain.