This is the last section of my discussion of the Virgin Birth from the Christology book.
This brings up the most important point regarding the Virgin Birth from the perspective of Lutheran dogmatics. In regards the inner unity and coherence of the analogia fidei, the Virgin Birth stands as an important corollary of the sola gratia. As we noted above, that John makes pains to state that the Christian's new spiritual birth occurs "not of natural descent, nor of human decision or a husband's will, but . . . of God" (Jn 1:13). If indeed salvation comes by grace, then it is not fitting that the Messiah's birth would come about by anything other than grace. In fact, it would appear that ecumenical differences regarding the status and nature of Mary are linked quite specifically to differences in the doctrine of grace.
Most notably, (as both Herman Sasse and Karl Barth have observed) the Roman Catholic understanding of Mary mirrors their synergistic concept of grace. According to the Catholic Catechism, the Virgin Mary was herself conceived without sin (described as being "born redeemed") and was filled with supernatural grace, both created and uncreated. The description of Mary being "full of grace" originates from the translation of Luke 1:28 in the Vulgate which reads "et ingressus angelus ad eam dixit ave gratia plena Dominus tecum benedicta tu in mulieribus." The words "gratia plena" ("full of grace") is the translation of the Greek "κεχαριτωμένη" which does not mean "full of grace" but "highly favored." In light of the fact that medieval (and modern) Roman Catholics came to understand "grace" to denote a supernaturally infused predicate of the human subject, it is easy to how theologians of that tradition came to understand Mary as they did. Similarly, the word "χαῖρε" (which is properly rendered as either "greetings" or "rejoice") is translated as "ave" ("Hail") makes it appear that Mary is being given some sort of adoration (or "hyperdulia" in Catholic thought, one step below worship in its proper sense)  rather than being exhorted to rejoice in God's grace.
Beyond the mistranslation of the angel's address to Mary, Roman Catholics historically found a basis for the Marian doctrines in the Vulgate's translation of the protevangelium. Genesis 3:15 is rendered in the Vulgate "inimicitias ponam inter te et mulierem et semen tuum et semen illius ipsa conteret caput tuum et tu insidiaberis calcaneo eius." The Douay-Rheims translation of the Vulgate renders this: "I will put enmities between thee and the woman, and thy seed and her seed: she shall crush thy head, and thou shalt lie in wait for her heel" (Emphasis added). In other words, it is the woman (read as Mary) who will crush the serpent's head, whereas in the original Hebrew (translated accurately in countless modern English Bibles) it is the male seed of the woman who will triumph over the serpent. This accounts for the frequent presence of statures of Mary crush a serpent in older Roman Catholic Churches.
The difference between the original Greek and the Vulgate (and how this translation was appropriated) illuminates the difference between the Roman Catholic and the Evangelical Lutheran understanding of both grace and the doctrine of the Church. From the Roman Catholic perspective grace is given us so that we might correspond to God's expectations and thereby gain salvation. This takes the form of meritorious behavior. Although "justification" (translated in the Vulgate Romans 3:28 as "iustificari," i.e. to "make righteous," rather than to "forgive" or "vindicate" as "δικαιοῦσθαι" as in New Testament and LXX Greek) cannot properly speaking be merited, although salvation itself can and must be. Catholics the term "justification" to mean moral regeneration that occurs in baptism through the reception of created and uncreated grace, not salvation promised for the sake of Christ. Salvation is not conceived in crass Pelagian terms, but in more subtle ones. There is rather an attempt to balance out the claims of nature and grace. If humans had no power to contribute to their salvation by cooperating with grace, then nature would be defective. If they did not need grace, the work of Christ and the supernatural power of God would be unnecessary. Furthermore, the merit of those who are redeemed is in a sense a participation in the merit of Christ, since Christ is casually responsible for their meritorious behavior.
Grace then is view as being inherently participatory. One of the major problems faced by this model of grace is the historicity of salvation. In other words, if salvation already happened and is complete as a previous historical event, it means that one is powerless to contribute to said event. Rather, as a saving event in the past, it can only be recognized and trusted in, which is why the New Testament urges faith or trust (πίστεως) in Christ's already completed work.
Doctrinally speaking, for Roman Catholic theology, the two main solutions to this problem are the sacrifice of the Mass and the Marian doctrines. Salvation happens because of the Incarnation, death, and resurrection of Christ. In the Mass, the believer not only receives grace, but also participates in Christ's death and self-offering to the Father irrespective of time and space. One is effectively taken back in time to the crucifixion so that one might be capable of offering themselves up collectively with Christ. Through this, the problem of distance from the crucifixion in that the Mass makes participation in the historical event possible. The distance of the believer from the Incarnation is not solved by individual participation in the event, but rather recognition that one person, Mary, the "Queen of Heaven" and the "highest of all creatures,"did have this opportunity. Like the believer who participates in their own redemption through the reception of grace (created and uncreated), so too Mary, being "full of grace," was born "redeemed" from original and actual sin. For this reason, she was able to actively participate in the work of redemption. In this sense, she is the unique Mediatrix of grace and worthy of hyperdulia, that is, worship that is not quite true worship ("latria," that is true worship, which is reserved for God alone). She is then, the model of the person, who after baptism is sinless participates in the merit of Christ by their own grace infused efforts.
Of course the difficulty with all this is the total lack attestation from the New Testament or even early Christian tradition (a point made by Barth). As we noted earlier, the actual text of the first chapter of Luke utterly contradicts the traditional Roman Catholic reading of it ("Hail" is really "greetings" or perhaps an admonition to "rejoice") or that she possess an infused supernatural quality known as "grace" rather than is "highly favored." In fact, what appears to be the case is that the genesis of Marian doctrines occurred mainly because of a misreading of a badly translated text. It is therefore highly unusual that the present Catholic Catechism continues to use these phrases (notably "Hail" and "Full of Grace" are cited as a biblical basis) despite the fact that modern Roman Catholic scholars and theologians now use the original Greek and Hebrew texts and acknowledge the faultiness of the Vulgate. One suspects that they might invoke the theory of the development of doctrine. But even if the Evangelical Lutheran Church accepted as legitimate the idea that the articles of the faith can be developed beyond their annunciation in the biblical authority, it is difficult to see how a verse of Scripture which teaches the very opposite of the doctrine of modern Catholicism can be believed to legitimate development.