The conception and birth of Jesus is a fundamental element of our faith

Is what we profess in the Creed true, then? - “I believe in one Lord Jesus Christ, the Only Begotten Son of God, …[who] by the Holy Spirit was incarnate of the Virgin Mary”?

The answer is an unequivocal yes. Karl Barth pointed out that there are two moments in the story of Jesus when God intervenes directly in the material world: the virgin birth and the resurrection from the tomb, in which Jesus did not remain, nor see corruption. These two moments are a scandal to the modern spirit. God is “allowed” to act in ideas and thoughts, in the spiritual domain - but not in the material. That is shocking. He does not belong there. But that is precisely the point: God is God and he does not operate merely on the level of ideas. In that sense, what is at stake in both of these moments is God’s very godhead. The question that they raise is: does matter also belong to him?

Naturally we may not ascribe to God anything nonsensical or irrational, or anything that contradicts his creation. But here we are not dealing with the irrational or contradictory, but precisely with the positive - with God’s creative power, embracing the whole of being. In that sense these two moments - the virgin birth and the real resurrection from the tomb - are the cornerstones of faith. If God does not have power over matter, then he simply is not God. But he does have this power, and through the conception and resurrection of Jesus Christ he has ushered in a new creation. So as the Creator he is also our Redeemer. Hence the conception and birth of Jesus from the Virgin Mary is a fundamental element of our faith and a radiant sign of hope.

Pope Benedict XVI, Jesus of Nazareth: The Infancy Narratives, chapter 2