The creeds say that Jesus is "fully God, fully man." That is hard to wrap your mind around. And I'm afraid many of us try to do it the wrong way. People commonly assume that the Virgin birth is what makes Jesus "fully God and fully man," but I think this is a mistake.
How important are the Virgin birth stories to the identity of Jesus? Could Jesus be declared the son of God without the Virgin birth stories? Only two of the four Gospels (Matthew and Luke) contain Virgin birth stories, so the answer is yes, Jesus can be declared by the Gospel writers as "the Son of God" without any account of His conception. Both Mark and John's Gospels do just that. Mark's Gospel possibly had a Christmas story that didn't survive, but, as it stands, his Gospel effectually tells the story of Jesus without the birth narrative. If we want to add some anecdotal evidence, there are thousands of Christians around the world who have limited or no access to Bibles but have become convinced of the Lordship and Deity of Jesus. They drew this conclusion without having access to the whole story. Millions of Christians do not have a personal Bible, and many of them came to faith in Jesus on the barest information. Most of these people have encountered Jesus in very real but rudimentary ways. Some of them heard a pastor in the village quote one bible verse (the only one he knew) and became believers. Some have experienced healing and deliverance in Jesus' name. Some have had dreams where Jesus introduced Himself to them. And they have all come to worship Jesus as God without necessarily knowing the birth narrative. So, how important is it?
The Virgin birth stories are very awkward and embarrassing to us modern westerners who boast of ourselves as scientific. We know how babies get conceived. How can we believe such a ridiculous story about a woman getting pregnant without a man? Many in our world scoff at this story. The irony is that many of those same people, who claim the scientific and moral high ground, are willing to speak and act as if a man could become pregnant! This absurd inconsistency should lead us to question the scientific and the moral high ground of the skeptics. Of course, many would stick to real science and say that the Virgin birth AND male pregnancy are impossible. And they are, of course, right.
So, why do Matthew's and Luke's Gospels contain these stories? Can we put them on the shelf as out-dated legends meant to enhance the image of the hero of the Gospels but not valid in the world enlightened by science? That would be a tragic mistake. Here is why:
The Gospel writers were not ignorant as we moderns often condescendingly assume. They, too, knew how babies come into being. As Historian/Theologian NT Wright points out, if Joseph didn't know where babies came from, he wouldn't have been planning to divorce his fiancé when he discovered her pregnancy. Furthermore, if Jesus' identity as the son of God can be established without the Virgin's birth stories, as Mark and John prove, why should Matthew and Luke add ridiculous stories to their Gospels unless they happened? They would not gain credibility from such fabrications. Throwing away the Virgin birth stories because they do not sit comfortably with our modern sensibilities is akin to throwing away pieces of an antique clock. You might deem the loose parts useless to discover later that they are the very things that make the clock unique and coveted.
I think the reason we have these stories is that these are the facts. It was a weird thing that took place, Matthew and Luke know this, but it happened. John's Gospel suggests that rumors were circulating that Jesus' birth was under some shadow of scandal (John 8:41). Matthew and Luke may be sharing the Virgin birth stories to say, we know it is weird, but this is what happened. There was no immorality involved.
Matthew's genealogy catalogs several strange and uncouth conceptions in the lineage of Jesus:
Peres and Zara were born to Tamar by her father-in-law, Judah.
Boaz was born to a Gentile prostitute.
Boaz married another Gentile named Ruth, who became the great grandmother of King David.
Solomon was born to King David through an adulteress relationship.
It seems that Matthew is adding the Virgin birth to this list of strange births in the genealogy of Jesus and chalking it up to another of the surprising and gracious acts of God in Israel's history. It seems that, while Jesus wasn't born under a cloud of immorality, God was willing to allow it to appear as such. The Christmas story is the beginning of a narrative where God enters our world in a way that He can receive shame, pain, slander, accusation, abuse, humiliation, torture, and death. It is the Gospel's point that Jesus should enter into the world of pain that we know, including public smears and shame, to release us from its power. Jesus wasn't born with a silver spoon in His mouth; neither was he born with a legitimate reason to feel shame. He was born into a world of accusation, and the war with the accuser began at conception.
The identity of Jesus as the son of God is not dependent upon the nature of His conception as though His DNA would reveal a heavenly pattern. Jesus is declared "God's son" through what He accomplishes for Israel. The scriptures also call King David "God's son," but we do not worship him as Divine. David was an extension of God's right hand, accomplishing God's will for Israel. But David's accomplishments had limitations. David did not usher in God's universal rule and reign over the earth. What makes Jesus God's son in a unifying way is the fact that Jesus accomplished for Israel what only God could achieve for Israel. David established the kingdom of Israel. But Jesus ushered in the Kingdom of God on earth as it is in heaven, which was the goal all along. David could set up a Kingdom with God's Help, but He couldn't eradicate evil from the planet or Israel alone! Jesus took the nation of Israel where only God could take it; into the new creation. And this is why the disciples began to worship Jesus. They could no longer see a line between what Jesus did and what God did. It was and is all the same. The basis of Jesus' identity as the son of God is grounded in His works, not His DNA.
