In A.D. 451 a large church council was convened to solve the problems raised in the controversies over the debate on the person of Christ. They met in the city of Chalcedon and a product of their meeting was the Chalcedonian Definition. This statement is considered the standard orthodox definition of the biblical teaching on the person of Christ by the Roman Catholic, Protestant, and Eastern Orthodox communions. It is brief enough to be stated here:
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 soul and body; consubstantial 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 taught us, and the Creed of the holy Fathers has handed down to us. (Schaff, Creed of Christendom 2:62-63; Grudem, Systematic, p 556)
The Chalcedonian Definition was important fighting against heresies of the day (Apollinarianism, Nestorianism, Monophysitism, etc) and allowed the church to grow closer in unity in doctrine and practice.
The Chalcedonian Definition affirmed that in the one person of Jesus Christ co-existed two natures. The eternal Son of God taking upon himself true human nature. These two natures, the divine and human, each with their own distinct properties could not be confused, changed, divided, or separated and yet they would be eternally united together in the one person and one subsistence.
Some may reflect on this statement and wish it said more. Perhaps they could have, but they definitely said plenty for us to consider, especially when we consider the mysteries of the Trinity and in particular the Incarnation of the Son of God. We must understand that the divine nature of Jesus is not different from that of the Father. He is not less in his divinity than the Father, that is why they affirmed Jesus is “consubstantial with the Father according to the Godhead”. The humanity of Jesus was a humanity like ours, absent of sin, so they would state that he was “consubstantial with us according to the Manhood”.
The Chalcedonian Definition also notedly states that these two natures (divine and human) are in one person and that which made them unique is not taken away when they are “concurring” in the one person and subsistence. Subsistence is from the Greek “hypostasis”. It can also be rendered as “being”. This gives is where the phrase “hypostatic union” is helpfully used. It means that union of the human and divine that are distinct but in separable in the one person of Jesus.
The Chalcedonian Definition is one of those works in history that we must come back to on occasion to remember that the church has used creeds and statements to tighten our doctrine and practice in a way the benefits the whole. Creeds and works such as this one, are also helpful as we continue to think about the mystery of the Trinity and the Incarnation of the Son of God.