The old church of St. Euphemia, sitting atop a hill in Chalcedon across the Bosphorus from Constantinople, hosted the fourth great council of the church in the fall of 451. The emperor called the bishops together to combat a series of heresies about the person of Christ and to formulate a creed that would unite Christianity.
The nature of Christ was the chief theological question of the first 400 years of church history. Christendom as a whole remained unified in an orthodox faith, but periodic assaults by heretics forced the church in its councils to state its definition of Christ. The Council of Nicaea in 325 had affirmed Christ as fully God. But how, then, could he also be truly human?
The Council of Chalcedon tackled that problem, and it wasn’t pretty. Bishops and delegates shouted at each other in rough-and-tumble debates, interrupting each other, losing their tempers, shouting down speakers, and wreaking havoc. In the end, however, it managed to affirm that Jesus: (1) is fully God; (2) is fully human; (3) is one person; and (4) possesses two distinct natures. The Chalcedon document, one of the most important in church history, says in part:
Following the holy fathers, we confess with one voice that the one and only Son, our Lord Jesus Christ, is perfect in Godhead and perfect in manhood, truly God and truly man, that he is of one substance with the Father as God, he is also of one substance with us as man. He is like us in all things without sin. This one and the same Christ, Son, Lord, Only-begotten is made known in two natures (which exist) without confusion, without change, without division, without separation. The distinction of the natures is in no way taken away by their union, but rather the distinctive properties of each nature are preserved.
The Council of Chalcedon thus affirmed that Jesus Christ is one person having both a divine and a human nature. He is one Lord. He is both God and man.
And with that, the council dissolved on November 1, 451.
Here is the great mystery of our religion: Christ came as a human. The Spirit proved that he pleased God, and he was seen by angels. Christ was preached to the nations. People in this world put their faith in him, and he was taken up to glory. (1 Timothy 3:16)
Robert J. Morgan, On This Day : 265 Amazing and Inspiring Stories About Saints, Martyrs & Heroes, electronic ed. (Nashville: Thomas Nelson Publishers, 2000, c1997). Nov. 1.