In 451, so much of the Faith was up for debate. Yes, they were closer to the time of Jesus but they were not always closer to the heart and mind of Jesus. The Council of Nicea in 325 had established that Jesus was divine without any doubt. It had rejected the idea that Jesus had been a creation--even a highly esteemed and very unique creation.With the deft strokes of words to paper, they excised heresy from the Church and insisted upon the real divinity of Jesus. To fail to do so would be to surrender the teachings of atonement, salvation, and all other christological questions. Though it is never the Church's first desire to cut out those it calls "brother," there comes a time when the Church must name brokenness for what it is. When those you might call "brother" or "sister" are not in communion with you, then you do not aid them by telling them that they are part of what they're not.
The Church met again in Chalcedon in 451. Now, the debate was the nature of Jesus'divinity. Having labeled Jesus divine had not brought an end to disputation--as nothing except Christ's second coming will do this--but, rather, changed the nature of the conversation. Now, there were those who said that Jesus was human with a divine soul and one divine nature. This allowed them to maintain Jesus' divinity and humanity without dirtying God's hands. It seemed clear that the way it worked was a divine nature dwelling within a corruptible human form. The problem was that this bordered dangerously close to the Gnostic believe that spirit was good and flesh was evil and, therefore, salvation was through escape of this world. For the Church, this wasn't a safe place to center their teaching. God had become human to redeem the world not to offer some metaphysical escape hatch.God had labeled creation "very good" in Genesis. Jesus had said he would come back to this world and also that he was "making all things new." This understandable desire--to avoid sullying God with our brokenness--was earnestly motivated but theologically flawed: it underestimated God's furious love for God's creation.
At Chalcedon, there was a stunning declaration:
Following the holy Fathers, we unanimously teach and confess one and the same Son, our Lord Jesus Christ: the same perfect in divinity and perfect in humanity, the same truly God and truly man, composed of rational soul and body; consubstantial with the Father as to his divinity and consubstantial with us as to his humanity; "like us in all things but sin." He was begotten from the Father before all ages as to his divinity and in these last days, for us and for our salvation, was born as to his humanity of the virgin Mary, the Mother of God.The fathers of the Church had declared that Jesus was not half and half and that this opinion though perhaps well-intentioned was poisonous and broken. Instead, they confessed that Jesus was fully human and fully divine in a way that transcended reason and understanding. This was a phenomenal statement that rested upon the foundation of a mysterious God who accomplished the impossible because of a love that transcended reason and understanding.
We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division, or separation. The distinction between natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person and one hypostasis.