The Chalcedonian Creed (A.D. 451)
Eutichus (the founder of Eutichianism) argued that Christ's human and divine natures merged to form a third composite nature. "The divine nature was so modified and accommodated to the human nature that Christ was not really divine...At the same time the human nature was so modified and changed by assimilation to the divine nature that He was no longer genuinely human." Thus, according to this teaching, Christ was neither fully human nor fully divine. This view was condemned by the Council of Chalcedon in A.D. 451.
The Chalcedonian Creed reads:
We, then, following the holy Fathers, all with one consent, teach men 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; 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 and one Subsistence, not parted or divided into two persons, but one and the same Son, and only begotten, God 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.