[5] In one of the translations into English, the key section, emphasizing the double nature of Christ (human and divine), runs: Following, then, the holy Fathers, we all unanimously teach that our Lord Jesus Christ is to us One and the same Son, the Self-same Perfect in Godhead, the Self-same Perfect in Manhood; truly God and truly Man; the Self-same of a rational soul and body; co-essential with the Father according to the Godhead, the Self-same co-essential with us according to the Manhood; like us in all things, sin apart; before the ages begotten of the Father as to the Godhead, but in the last days, the Self-same, for us and for our salvation (born) of Mary the Virgin Theotokos as to the Manhood; One and the Same Christ, Son, Lord, Only-begotten; acknowledged in Two Natures unconfusedly, unchangeably, indivisibly, inseparably; the difference of the Natures being in no way removed because of the Union, but rather the properties of each Nature being preserved, and (both) concurring into One Person and One Hypostasis; not as though He was parted or divided into Two Persons, but One and the Self-same Son and Only-begotten God, Word, Lord, Jesus Christ; even as from the beginning the prophets have taught concerning Him, and as the Lord Jesus Christ Himself hath taught us, and as the Symbol of the Fathers hath handed down to us.The Definition implicitly addressed a number of popular heretical beliefs.
[3] The Chalcedonian Definition was written amid controversy between the Western and Eastern churches over the meaning of the Incarnation (see Christology).
Even though Chalcedon reaffirmed the Third Council's condemnation of Nestorius, the Non-Chalcedonians always suspected that the Chalcedonian Definition tended towards Nestorianism.
The formal definition of "two natures" in Christ was understood by the critics of the council at the time, and is understood by many historians and theologians today, to side with western and Antiochene Christology and to diverge from the teaching of Cyril of Alexandria, who always stressed that Christ is "one".
However, a modern analysis of the sources of the creed (by A. de Halleux, in Revue Theologique de Louvain 7, 1976) and a reading of the acts, or proceedings, of the council show that the bishops considered Cyril the great authority and that even the language of "two natures" derives from him.