Question: I know a protestant who argues that there was nothing significant about the Virgin Mary, and that just about any woman who was a believer "would have been just as good a selection.” How would you reply to someone that said there was nothing special about the Virgin Mary and basically anyone else could have done what she did?
There is of course a great deal that could be said about the Tradition of the Church to contradict what this protestant said, but when arguing with protestants, the arguments that they will find most persuasive are arguments from Scripture.
I would point out, first off that he has no basis in Scripture for the assertion that any other woman would have been just as good of a selection. Scripture does not tell us explicitly why God chose the Virgin Mary, but when we see her obedience, humility, love, and long-suffering in the Gospels it is clear that she was not just a randomly chosen Jewish girl, but rather an extremely holy woman.
Secondly, there are three places in the first chapter of the Gospel of Luke alone in which it is made clear that the Virgin Mary was "special":
1. The Archangel Gabriel greeted her with the words: "Rejoice, thou that art full of grace, the Lord is with thee: blessed art thou among women" (Luke 1:28). It is no small matter to be full of grace, for the Lord to be with you, and to be the most blessed of women.
2. When the Virgin Mary went to visit St. Elizabeth, the mother of St. John the Baptist, we are told: "And it came to pass, that, when Elizabeth heard the salutation of Mary, the babe leaped in her womb; and Elisabeth was filled with the Holy Spirit: and she spake out with a loud voice, and said, Blessed art thou among women, and blessed is the fruit of thy womb. And whence is this to me, that the mother of my Lord should come to me? For, lo, as soon as the voice of thy salutation sounded in mine ears, the babe leaped in my womb for joy. And blessed is she that believed: for there shall be a performance of those things which were told her from the Lord" (Luke 1:41-45). At the sound of the Virgin Mary's voice, Elizabeth was filled the Holy Spirit. We are again told that she is the most blessed of women, she is called the mother of the Lord, and Elizabeth states that she is unworthy of the honor that the mother of her Lord should visit her. She also states that she is blessed because of her faith.
3. The Virgin Mary herself, in her Magnificat, said "...from henceforth all generations shall call me blessed" (Luke 1:48). So I would ask your protestant friend why, if every generation will call her blessed, he refuses to do so along with them?
Protestants do not give much credence to Tradition, but they have a harder time dismissing what the early fathers of the Church had to say, and one of the earliest was St. Ireneaus of Lyons (ca. 130 - 202 AD). St. Ireneaus grew up in Smyrna, and as a boy heard the preaching of St. Polycarp, who was a disciple of the Apostle John. In his famous work, Against Heresies, he speaks of the role that the Virgin Mary played in our salvation as the new Eve, whose obedience and faith undid the disobedience of our first mother:
"In accordance with this design, Mary the Virgin is found obedient, saying, “Behold the handmaid of the Lord; be it unto me according to thy word.” But Eve was disobedient; for she did not obey when as yet she was a virgin. And even as she, having indeed a husband, Adam, but being nevertheless as yet a virgin (for in Paradise “they were both naked, and were not ashamed,” inasmuch as they, having been created a short time previously, had no understanding of the procreation of children: for it was necessary that they should first come to adult age, and then multiply from that time onward), having become disobedient, was made the cause of death, both to herself and to the entire human race; so also did Mary, having a man betrothed [to her], and being nevertheless a virgin, by yielding obedience, become the cause of salvation, both to herself and the whole human race. And on this account does the law term a woman betrothed to a man, the wife of him who had betrothed her, although she was as yet a virgin; thus indicating the back-reference from Mary to Eve, because what is joined together could not otherwise be put asunder than by inversion of the process by which these bonds of union had arisen; so that the former ties be cancelled by the latter, that the latter may set the former again at liberty. And it has, in fact, happened that the first compact looses from the second tie, but that the second tie takes the position of the first which has been cancelled. For this reason did the Lord declare that the first should in truth be last, and the last first. And the prophet, too, indicates the same, saying, “instead of fathers, children have been born unto thee.” For the Lord, having been born “the First-begotten of the dead,” and receiving into His bosom the ancient fathers, has regenerated them into the life of God, He having been made Himself the beginning of those that live, as Adam became the beginning of those who die. Wherefore also Luke, commencing the genealogy with the Lord, carried it back to Adam, indicating that it was He who regenerated them into the Gospel of life, and not they Him. And thus also it was that the knot of Eve’s disobedience was loosed by the obedience of Mary. For what the virgin Eve had bound fast through unbelief, this did the virgin Mary set free through faith" (Against Heresies 3:22:4).
So the attitude taken by your protestant friend is neither Biblical, nor consistent with the view found in the early Church.