Christmas is the feast of the incarnation. In Christmas we do celebrate the nativity or birth of Christ, but what we are celebrating is not simply Jesus "birthday," the way we celebrate our own birthdays. We are celebrating the mystery of Emmanuel, God-with-us, God revealed in time and space. Each week in the creed we say "by the power of the Holy Spirit he was born of the Virgin Mary and became man," and the instructions say we are supposed to bow at those words, but on Christmas, the instructions say to genuflect. Why? Because those words proclaim the incarnation, that God became human. So what is the incarnation all about?

St. Athanasius, one of the great fathers and theologians of the Church, tells us:

The Son of God became human so that we might become God.

Obviously we do not become God in the way that God is God, but we become God-like, we are divinized. The eastern Christian tradition has done a much better job of reminding people of this fact than our western tradtion has done, as the west has tended to focus much more on the incarnation as a remedy for sin (it is both). The eastern tradition has a beautiful Greek word, theopoesis or theosis, literally to make divine, to describe this process. The word is usually translated as divinization or deification. We partake in the divine nature. St. Irenaeus puts it another way:

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.

In the liturgy itself, when the priest pours a bit of water into the wine, he says:

By the mystery of this water and wine may we come to share in the divinity of Christ, who humbeled himself to share in our humanity.

We do not usually here him say this because he says it in a low voice to himself, but it proclaims the meaning of the incarnation - that God and humanity are united in and through the person of Christ.

Another axiom of our faith tells us that what Christ is by nature, we are by adoption. We cannot understand who Jesus is as Son of God without understanding our own identity and calling as children of God. "Son of God" does not appear in the Bible for the first time in reference to Jesus. In the Hebrew Scriptures, Israel is the Son of God (e.g., see Exodus 4:22-23). Likewise King David is referred to as a Son of God, as are other leaders and prophets. The phrase indicates both intimacy with God and the desire/need for obedience to God, a willingness to do God's will. Jesus is perfectly the Son of God in this way because he is both human and divine, and through our union with him and our sharing in his divinity, we are brought into that relationship with God as well. What he is by nature, we are by adoption. We become children of God, divinized and empowered to do the will of God by that intimate, loving relationship. Christmas is not simply a celebration of who Jesus is; it is a celebration of who we are.