Matthew 1:18-25. Here we read of the angel's appearance to Joseph, letting him know that the child Mary, his betrothed, is carrying, is of the Holy Spirit. This fulfills the word of Isaiah the prophet: "Look, the virgin shall conceive and bear a son,
While my denominational tradition is non-creedal, and we don't recite the Apostles Creed, the majority of the Christian world does recite the creeds, and thus affirm in one form or another the statement about Jesus: " I believe in Jesus Christ, God's only Son, our Lord, who was conceived by the Holy Spirit, born of the Virgin Mary," For at least some modern Christians this is simply nonsense. It must be a myth, so why say the words? It's just a relic of a distant past, when people still believed in a three-storied world. That may be true, in a fashion, and yet is there something of value to be heard in this confession?
Karl Barth is one who believes this to be true. Since I like Barth, and find him intriguing, I appreciate his words of wisdom. He answers the question of whether we should believe this statement with a firm and joyful yes. He writes in the Dogmatics in Outline:
If we wish to understand the meaning of "conceived by the Holy Ghost and born of the Virgin Mary," above all we must try to see that these two remarkable pronouncements assert that God of free grace became man, a real man. The eternal Word became flesh. This is the miracle of Jesus Christ's existence, this descent of God, from above downwards---the Holy Ghost and the Virgin Mary. This is the mystery of Christmas, of the Incarnation. At this part of the Confession that the Catholic Church makes the sing of the Cross. And in most various settings composers have attempted to reproduce this et incarnatus est. This miracle we celebrate annually, when we celebrate Christmas.
If I to grasp this miracle should will,So stands my spirit reverently still.
Such in nuce is God's revelation; we can only grasp it, only hear it as the beginning of all things. [Dogmatics in Outline, p. 96]
It is something of a mystery, and it requires of us to let go of some of our scientific rigor. It doesn't mean entering an irrational world, but it does involve recognizing that there are somethings that science simply can't explain, nor can reason. We must instead respond in faith, recognizing that the confession invites us to affirm that God is with us in Christ. This is the message of Christmas. Remember that the Creed also invites us to affirm the premise that Christ is fully God and fully human. Thus the mystery of faith!