Preface III of The Nativity of the Lord

For more information on the Preface in general, see The Eucharistic Prayer (2) and The Eucharistic Prayer (3)

The Incarnation and Nativity of the Lord aren’t just historical events that had external consequences for us. When Christ assumed human nature, divine nature and human nature became “bridged” in the Person of Christ, and human nature received the opportunity to be influenced by divine nature in a wondrous exchange.

The exchange in the Incarnation of the Word

St. Peter in his second epistle teaches us that the power of Christ makes us partakers of divine nature:

“His divine power has granted to us all things that pertain to life and godliness, through the knowledge of him who called us to his own glory and excellence, by which he has granted to us his precious and very great promises, that through these you may escape from the corruption that is in the world because of passion, and become partakers of the divine nature.” (2 Peter 1:3-4).

The Catechism teaches us that this, in fact, was why the Word became flesh (n.460):

“The Word became flesh to make us ‘partakers of the divine nature’: ‘For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God.’ ‘For the Son of God became man so that we might become God.’ ‘The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods.”

In Eastern Christian tradition this is described as theosis; as we are transformed by grace into new life through Christ we are, to a certain degree, divinized. We are restored, communion with God is made possible once again, and we are transformed by grace.

“For through him the holy exchange that restores our life has shone forth today in splendor: when our frailty is assumed by your Word not only does human mortality receive unending honor but by this wondrous union we, too, are made eternal.”

That frail little baby born in Bethlehem made frail human nature, wounded in its natural powers by sin, strong again and apt for eternity. Sin condemned us to death; Christ in his Incarnation established a “beachhead” in human nature that sin could no longer corrupt, and from that “beachhead” he draws us back, one by one, to a healed, restored, and divinized human nature. We still bear the scars of sin, but the wounds have been healed because that frail little baby infused healing into our nature by assuming it.

St. Peter in his second epistle also said what we should do in gratitude for being made partakers in the divine nature:

“For this very reason make every effort to supplement your faith with virtue, and virtue with knowledge, and knowledge with self-control, and self-control with steadfastness, and steadfastness with godliness, and godliness with brotherly affection, and brotherly affection with love” (2 Peter 1:5-7).

This theosis is not a done deal; it’s an opportunity Our Lord offers us. Exchange goes both ways. To the degree we offer him our humanity lived in a truly human way (virtuously, wisely, knowledgably, with self-control, godliness, brotherly affection, and love) we receive in exchange a human nature transformed by grace in Christ. This is the best birthday gift we can give Our Lord at Christmas.