The notion of Mary, being a virgin, giving birth to Jesus the Christ is necessary for good theology. When one takes into account that, as the Spirit of God overshadowed the surface of the waters (Gen. 1:2) generating life, so the Spirit of God overshadowed Mary (Luke1:35) likewise generating life, a virgin birth is altogether probable. To understand the necessity of the virgin birth we must begin with a profound presupposition. The Jesus that was born to Mary is the eternal Word of God who was at work speaking forth creation (John 1:1-3, 14). The Word of God created Adam and Eve, who were created in the image of God and to whom it was given to be the expression of God on earth (Gen. 1:26-28).
When Adam and Eve sinned, they lost that expression. Though they lost the rite of expression, it was still given to humanity to be that expression in all creation. Since, therefore, the rite of expression was given to humanity it must be a member of humanity that redeems that expression. Nothing else on earth was given the rite of expressing God. Angels could not redeem the expression to humanity, obviously, because they are of a different order of creation and not human. God Himself, in His incorporeal essence, could not redeem humanity for the very same reason. Again, it must be a human being that redeems humanity since it was humanity that forfeited the expression. But no human being was able to do so because all humanity suffers under the sin nature brought about by the sin of Adam and Eve. It is ironic to conclude that humanity had to save itself, but was unable to do so for the very reason it had to do so. In other words, humanity could not save itself because of the sin nature, which nature was the reason that humanity had to save itself.
Enter, here, the continually existent Word of God. The invisible Word of God put on flesh and was born as a human being. The virgin birth is necessary in order to avoid the irony of the sin nature. Seeing that Mary was overshadowed by the Holy Spirit, and not impregnated by human means, Jesus was born without the sin nature. In fact, it is the only way to be born without the sin nature that so plagues humanity. Thus, though He was tempted as every human being, Jesus lived a sinless life having not caved to temptation because of the lack of the sin nature (which causes the rest of humanity to so cave).
So, while Jesus was/is in fact God (the preexistent Word), He came to earth in the form of a man in order to save humanity. By living a perfect life He regained the expression of God. He, having suffered to the point of death on a cross, was raised from the dead for the redemption of humanity. He now sits at the right hand of God (in human form) for the reconciliation of humanity with God. He is, technically speaking, as God’s express image, the Head of the Body; which body humanity is, as we express the image of Christ, who returned us to the image of God. This magnificent plan necessitates the virgin birth of the Word of God in human form.
