According to A Wesleyan-Holiness Theology by J. Kenneth Grider, page 319-321, Importance of the Doctrine. The doctrine of Jesus Christ's conception in a virgin woman's womb is important on a number of bases.
For one thing, and perhaps most significantly, it is important as indicating Christ's deity. If Christ had been born through the participation of a male, He would have been human only. Born by stupendous miracle as He was, through Mary's conceiving by a special act of "the Holy Spirit" (Matt. 1:20; Luke 1:35), His deity is assured. As Karl Barth has said, the Virgin Conception means that Christ is "founded in God." The angel Gabriel said, "The Holy Spirit will come upon you, and the power of the Most High will overshadow you" (Luke 1:35).
The Virgin Conception is also significant as assuring the Incarnation. Again, if Christ had been born through the participation of a human father, the enfleshment of the Deity in Jesus of Nazareth would not have occurred. With an ordinary human conception, we would have had only the ordinary and usual wonder of a human-only person being born. God the Father might have conceived another strategy to achieve an Incarnation of the Deity with humanity. Perhaps He was not limited to Spirit conception as the means to the Incarnation. Yet, according to Holy Scripture, that is the method He chose. And if that method is denied, the Incarnation cannot then still be affirmedalthough such theologians as Emil Brunner and Rudolph Bultmann has attempted precisely this. Another means to the Incarnation would be simply a human inventionan invention designed to net us Incarnation without the embarrassment of Spirit conception in a virgin's womb.
A third importance of the Virgin Conception is that it assures Christ's humanityHis full humanity, if you please. Through the Spirit's power, Christ was conceived in and born from Mary's womb. He was not poured through her womb, as the docetic Gnostics said. He was gestated through an entire nine-month period. In this way, He who was above us was made of uswas made one with us. In this way, He was make very flesh with us. In this way, also, He became what He seemed to be: a human being who thirsted, hungered, wept, suffered, and died, and was raised bobily.
A fourth importance of the Virgin Conception is that it suits God's usual way of accomplishing things, not by fiat, but by human participation. He could have had His Eternal Son assume human flesh without the participation of a woman, as angels at times seem to have done (Genesis 18-19). But He did not do this. Instead, from outside and above the human experience, He entered into human form and life and experience. From outside and above the historical, He entered into the historical. All this is in keeping with His usual way of acting creatively and redemptively on our behalf.
A fifth factor in the importance of the doctrine of the virgin conception of christ is its harmony with a wide range of supernatural events in our Christian faith. If respect for science causes us to oppose the Virgin Conception, the door is opened for a wider ersion of faith. Next to go may be Christ's miracles, His physical resurrection, the efficacy of the sacraments, the objective value of prayer, etc. If science cancels the supernatural, Christianity will be reduced to a religious humanism void of redeeming power.
A sixth basis for the importance of the Virgin Conception is that it gives the whole Christmas story a facticity basis. The actual, factual birth of the virgin-conceived Jesus is what Christmas, the principal holy day of Christianity and of the Western world generally, is all about. The Christmas mother, Mary; the Christmas miracle, Virgin Conception; the Christmas mystery, Incarnation; and the Christmas message, redemption through Jesusthese things are all bound up in this doctrine, this understanding, this confidence, this heady joy.
TheVirgin Conception, then, is richly important theologically and is, as a doctrine, in keeping with a historical Resurrection. It also figures significantly in why the Atonement made Christ a Savior instead of a mere martyr.