What then did the Lord bring to us by His advent?
St. Irenaeus raises this question in the third book of Against Heresies, anticipating what some people might wonder if Christ’s life and sufferings were prophesied in the Old Testament. The question is: if all this was known beforehand, then what exactly did Christ bring? Irenaeus responds:
He brought all newness, by bringing Himself who had been announced. For this very thing was proclaimed beforehand, that a novelty should come to renew and quicken mankind (Against Heresies, 3.34.1).
As the Lord declares through Isaiah, “See, I am doing something new!”
Now it springs forth, do you not perceive it?
In the wilderness I make a way,
in the wasteland, rivers (Isaiah 43:19).
Jesus says the same in Revelation 21:5, “Behold, I make all things new.”
Newness. Everything about Christmas sparkles with this joyful hope. A virgin conceives not with a man but through the power of God. A virgin gives birth. And the new child is something both prophesied yet entirely unforeseen: God in the flesh — something so new that even the angels came rushing down from heaven to witness it (see Luke 2:8-21 and 1 Peter 1:12).
All this newness was centered in the person of Christ Himself. Every other person who has walked the earth in the flesh has been an individual person composed of a human body and soul. One person, one nature. Christ shared in our humanity yet was entirely different: one person, two natures — fully man and fully God, united but unmixed. So great and dazzling is the truth of the Incarnation that it took a full eight ecumenical councils to fully define it and fend off heretical misunderstandings.
Christ experienced the fullness of humanity except sin (Hebrews 4:15). At the same time, He was utterly unique — one of a kind. As St. John of Damascus explains in The Orthodox Faith,
But a common form cannot be admitted in the case of our Lord Jesus Christ. For neither was there ever, nor is there, nor will there ever be another Christ constituted of deity and humanity, and existing in deity and humanity at once perfect God and perfect man (The Orthodox Faith, 3.3).
The mystery of the Trinity discloses yet a further mystery: the Triune communion of God Himself. As the catechism explains:
Everything that Christ is and does in this nature derives from ‘one of the Trinity.’ The Son of God therefore communicates to his humanity his own personal mode of existence in the Trinity. In his soul as in his body, Christ thus expresses humanly the divine ways of the Trinity.
The manner in which Christ, in His humanity, experienced the Trinity is therefore utterly different than any other person in history because He is one of the three persons in the Trinity.
Now, usually when we encounter something incredibly rare or one of a kind, its uniqueness is closed in on itself. An endangered species is at risk of dying out. A living fossil is the last of its kind. A rare form of a plant or animal species stands out because it is so different than the others.
So also within the human species: someone of exceptional height, short stature, strength, or genius is a blip on the radar screen. Their specialness is limited to them. Their advent and eventual death in human history doesn’t fundamentally change the rest of us. Albert Einstein and Andre the Giant have come and gone. They amazed and inspired us, but there are not more giants or more geniuses because of them.
With Christ it is all-together different. The union of God and man wrought in His person was so radically new and earth-shattering that it fundamentally transformed what it meant to be human.
In His earthly ministry, Christ called us to a new way of being. First, we’d have to be born again to experience this new life (John 3:3). He then promised us living water that would never leave us thirsting (John 4:14). And He called on us to dwell within His very being (John 15:5), so much so that we would even His flesh and drink His blood (John 6).
After Christ, it was not enough to speak of human nature on its own, just as the story of Christ would be woefully incomplete if we spoke only of His humanity. Henceforth, there would be two planes of human existence: nature and grace. And this grace, according to St. Thomas Aquinas, is a gift that touches our souls, enabling us to participate in the divine goodness. By uniting divinity to humanity, Christ left open the door to God for all of us.
So no, there will never be another Incarnation, but humanity will never be the same either. The Incarnation stands apart like the brightest of stars, lighting our path forward to the newness it offers to each of us.