Chalcedonian Creed
In response to Nestorian teachings, the Chalcedonian formulation defines that Christ is "acknowledged in two natures", which "come together into one person and one hypostasis".
The Council of Ephesus in AD 431 forbade the making of any new creed. The Council of Chalcedon, which met in 451 to confront new errors, chose to issue a decree to affirm earlier versions of the Nicene Creed (both the 325 and the 381 versions) and also to offer a concise clarification regarding the church’s teaching about the person of Christ. The council then promptly banned anyone else from making a new creed. While not a complete creed of the Christian faith, this clarifying statement, or definition was adopted by the eastern and western church as a response to several heresies regarding the nature of Christ.
This clarification was the clearest statement to date on the person of the Lord Jesus Christ. It confesses who Christ is now: God and man, one person in two natures (hence its language of both natures coming together in one person). Unlike earlier creeds, it does not emphasize the actual event of the incarnation, the person of the Son taking to himself humanity. Famously, it also offers a series of denials about Christ when it teaches that the natures of Christ “undergo no confusion, no change, no division, no separation.” This “negative” theology reflects a belief among many Christians that much of what we say about God. and perhaps the best of what we say about God, consists in saying what he is not.
The Creed
The Chalcedonian formulation was a vindication of the Nicene Creed of 381.
Therefore, following the holy fathers, we all unite in teaching that we should confess one and the same Son, our Lord Jesus Christ. This same one is perfect in deity, and the same one is perfect in humanity; the same one is true God and true man, comprising a rational soul and a body. He is of the same essence (homousios) as the Father according to his deity, and the same one is of the same essence (homousios) with us according to his humanity, like us in all things except sin. He was begotten before the ages from the Father according to his deity, but in the last days for us and our salvation, the same one was born of the Virgin Mary, the bearer of God (Theotokos), according to his humanity. He is one and the same Christ, Son, Lord, and Only Begotten, who is made known in two natures (physeis) united unconfusedly, unchangeably, indivisibly, inseparably. The distinction between the natures (physeis) is not at all destroyed because of the union, but rather the property of each nature (physis) is preserved and concurs together into one person (prosopon) and subsistence (hypostasis). He is not separated or divided into two persons (prosopa), but he is one and the same Son, the Only Begotten, God the Logos, the Lord Jesus Christ. This is the way the prophets spoke of him from the beginning, and Jesus Christ himself instructed us, and the Council of the fathers has handed the faith down to us.