In the grandest of all the Christmas narratives, God's way of peace amidst human hostility is prefigured, waiting to be fleshed out as the story of Jesus is told.
And the Word became flesh and dwelt among us, and we have seen his glory...
A simple description of incarnation is: glory. Unique glory "as of the only son from the Father". Incarnation, therefore, does not name what we see when we see a human being behaving like God. Incarnation names what we see when we see Jesus. Compared to this seeing, all other seeing is blindness. By the grace of this seeing, we see everything else in the light of the glory unveiled. By the grace of this glory, we too are called to share in it. What is this glory?
Christ’s moment of most absolute particularity – the absolute dereliction of the cross – is the moment in which the glory of God, his power to be where and when he will be, is displayed before the eyes of the world. (D.B. Hart)
In short, the cross of Christ is the glory of God. It is on the cross that the narrative of violence is once-for-all confronted by the narrative of peace. Here light shines in darkness, and darkness cannot overcome it. Here glory is seen as the Giver who is himself the act of giving and the gift itself. This is what it means to say "incarnation". This is also the story of God's peace - it is relentless offering, relentless giving, relentless sacrifice for the sake of even the worst other. It ends in death - but it begins again with resurrection, by which Jesus is announced as the true lord and form of all creation and by which all creation is made new. Hart can thus say,
The resurrection – far from liberating Christ’s otherworldly essence from the servile form in which it has hitherto been hidden – vindicates and imparts again the whole substance of Christ’s earthly life, the shape of its particularity, which is, precisely in its humble and slavish form, an overcoming of earthly powers. His is a pattern that sinful history cannot accommodate (which is why pagan critics from Celsus to Nietzsche can find no way properly to account for the figure of Christ or for the force of his presence in time), but this is not to say that he must in consequence withdraw from history; rather, he initiates a real counterhistory, a new practice and new form of life that is – as it happens – the true story of the world.
The peace promised at Christmas only makes sense in light of the peace that Jesus breathes over his disciples after his resurrection. Or to quote the best thing I've read about Christmas in a while, "the real meaning of Christmas is Easter."
Yet the story does not end there. The peace pronounced by Jesus is followed by a commissioning; by vocation: "As the Father has sent me, even so I am sending you." In once sense, it is finished. In another sense, it has only just begun. The church is not incidental to the peace made possible by Christ. The church is a witness to what is already true and to what will be even truer in the future. But such witnessing does not take the form of an idle spectator. It is -- it must be and can only be -- the witness of participants:
The church exists in order to become the counterhistory, nature restored, the alternative way of being that Christ opens up: the way of return. (Hart)