The thought of the Virgin Mary giving birth to Jesus the Christ is not simply a tradition, but a necessity 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) generating life likewise – 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 none other than the eternal Word of God that spoke creation into existence (John 1:1-3, 14). This incorporeal Word created Adam and Eve in the image of God, to whom it was given to be the expression of God on earth (Gen. 1:26-28).
When Adam and Eve disobeyed, 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 humanity which redeems that expression; nothing else was given the rite of expressing God. Angels could not redeem the expression in humanity, obviously, because they are of a different order 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 nature of depravity brought about by the disobedience of Adam and Eve.
It is ironic to conclude that humanity had to rescue itself, but was unable to do so for the very reason that it had to do so. In other words, humanity could not rescue itself because of the nature of depravity, which nature was the reason that humanity had to rescue itself.
Enter, here, the continually existent Word of God. The invisible Word of God put on flesh and was born, bodily, as a human being. The virgin birth is necessary to avoid the irony of the corrupt nature. Seeing that Mary was overshadowed by the Holy Spirit, and not impregnated by human means, Jesus was born without the depraved nature. In fact, it is the only way to be born without the corruption of depravity that so plagues humanity. Thus, though He was tempted as every human being, Jesus lived a life having not caved to temptation because of the lack of the nature of depravity (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 human in order to rescue humanity. By living perfectly 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 creation 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 – the clothing of the Word of God with human form, though without the depraved corruption, necessarily.