The Anathemas of the Second Council of Constantinople, No. 4

If anyone says that the union of the Word of God with man was only according to grace or function or dignity or equality of honor or authority or relation or effect or power or according to his good pleasure, as though God the Word was pleased with man, or approved of him, as the raving Theodosius says; or that the union exists according to similarity of name, by which the Nestorians call God the Word Jesus and Christ, designating the man separately as Christ and as Son, speaking thus clearly of two persons, but when it comes to his honor, dignity, and worship, pretend to say that there is one person, one Son and one Christ, by a single designation; and if he does not acknowledge, as the holy Fathers have taught, that the union of God is made with the flesh animated by a reasonable and intelligent soul, and that such union is according to synthesis or hypostasis, and that therefore there is only one person, the Lord Jesus Christ one of the holy Trinity -- let him be anathema. As the word "union" has many meanings, the followers of the impiety of Apollinaris and Eutyches, assuming the disappearance of the natures, affirm a union by confusion. On the other hand the followers of Theodore and of Nestorius rejoicing in the division of the natures, introduce only a union of relation. But the holy Church of God, rejecting equally the impiety of both heresies, recognizes the union of God the Word with the flesh according to synthesis, that is according to hypostasis. For in the mystery of Christ the union according to synthesis preserves the two natures which have combined without confusion and without separation.

[Here are brief explanations of three of the heretical views mentioned here.

Nestorianism was the view that there were two distinct persons in Christ: a human person, and the divine person. To be fair, it should be noted that Nestorius, whose name this view bears, probably didn't hold to this view.

The view taught by Apollinaris, known as Appollinarianism, was that Christ was one person consisting of a divine nature in a human body. He had no human mind or spirit.

The view of Eutyches, called Monophytism, who taught that the human nature of Christ joined with the divine nature in such a way that the human nature was absorbed into the divine nature, and a third sort of nature resulted. There was a variant of this view that taught that Christ's human nature disappeared into the divine, and the resulting nature was only divine.]

Questions? Comments? Calling all nitpickers!