The dogma that Mary is perpetually a virgin (defined at the Second Council of Constantinople in the sixth century) finds its origin, like all Catholic dogma, in the teaching of the apostles.
To see it in Scripture, we must, of course, get past both hyper-sexualized contemporary culture (which can scarcely imagine virginity at all) and the assumptions of much of Protestantism which reads the New Testament with the conviction that it “disproves” the Perpetual Virginity of Mary. When we do this (by reading Scripture as the earliest Christians did), we discover that, in fact, there is no basis for rejecting her Perpetual Virginity and plenty of reason to believe that the early Christians were preserving a real historical memory.
For, in fact, every text adduced to “prove” Mary had other natural-born children encounters some fatal difficulty when we look closely.
So, for instance, attempts to prove siblings for Jesus from Matthew 1:25 suffer from the fatal ambiguity of the word “until.” Indeed, it was Martin Luther who pointed out that when Scripture says David had no relations with Michal until the day of her death, it does not mean he had relations with her afterward. Similarly, neither is Matthew saying anything beyond “Mary conceived Jesus in virginity.”
In the same way, every text concerning Jesus’ “brothers and sisters” was consistently read by the early Church to mean something other than siblings. And with good reason, for Matthew and Mark name James, Joseph (or “Joses” depending on the manuscript), Simon, and Judas (i.e., “Jude”) as “brothers” of Jesus. But Matthew 27:56 says that at the cross were Mary Magdalene and “Mary the mother of James and Joseph,” whom he significantly calls “the other Mary” (Matt. 27:61) (i.e., the Mary who was not Mary the Mother of Jesus). John concurs with this, telling us that “standing by the cross of Jesus were his mother, and his mother’s sister, Mary the wife of Clopas, and Mary Magdalene” (John 19:25, emphasis added). That is, James, Jude and their brothers are the children of “the other Mary,” the wife of Clopas, not Mary, the Mother of Jesus. That’s why, as Eusebius records in the fourth century, James’ successor as bishop of Jerusalem was none other than “Symeon, son of Clopas.” Why him? Because James and Symeon/Simon were the sibling children of Clopas and the “other Mary.” In short, there’s no There there when it comes to evidence against the Perpetual Virginity of Mary.
There is, however, evidence for it.
Consider: Why does a betrothed woman like Mary marvel at the prospect that she shall have a son? This is a promise that has been made to other women in Jewish history such as Sarah, Hannah, and the Shunammite woman (cf. Gen. 18; 1 Sam. 1; and 2 Kgs. 4). All of them understood the promise to mean, “You and your husband will conceive a child.” So why should the same promise astonish Mary, a young woman who also plans to marry—unless she had already decided to remain a virgin throughout her life?
Joseph, likewise, behaves in a way that supports the traditional view of Mary. Despite the modern tendency to assume he did not believe Mary, the earliest Christian Fathers take it for granted that he did—and that he was overwhelmed with fear at the prospect. In short, he sought to put her away (not stone her to death as the law prescribed) because he was afraid of the responsibility of being the father of the one the angel called “Son of the Most High God” (see sidebare). This is certainly supported by the words of the angel to Joseph. For the angel in the dream does not say, “Don’t suspect Mary of adultery” but “Do not fear to take Mary your wife” (Matt. 1:20, emphasis added). He addresses Joseph as “son of David,” thereby reminding him that the Messiah is to come through David’s line. In short, the angel reminds Joseph that this task has been appointed to him by God, despite Joseph’s sense of unworthiness. That sense of reverence for Mary as a sort of “second Ark of the Covenant” played out in his embrace of celibacy for the sake of the Kingdom of God.
This is also borne out by the fact that Jesus, in his final moments of earthly life, gives Mary into John’s care—an act that makes no sense if Jesus had siblings.
Now the interesting thing is that the Church does not merely see in Mary’s Perpetual Virginity an interesting historical tidbit. Rather, it sees her Perpetual Virginity as significant and packed with divine meaning for us. That makes sense, since the Perpetual Virginity of Mary is, of course, the extension of the Virgin Birth and the Virgin Birth is, according to the prophet Isaiah, a “sign” (Isaiah 7:14). Therefore, her Perpetual Virginity is a sign as well and is, as the Fathers consistently taught, a fulfillment of the prophets too. For the Incarnation of Jesus Christ is likened in Scripture to God coming to dwell in his temple in majesty. That’s why Jesus says, “Destroy this temple and in three days I will raise it up” (John 2:19). He is speaking of the temple of his body. So the Old Testament moments in which God descends in majesty on the tabernacle and the temple in the pillar of cloud (cf. Ex. 40:34–38; 1 Kgs. 8:10–11) are revealed to be prophetic foreshadows of when God would truly come to dwell in his temple: when the Word became flesh and tabernacled among us (John 1:14).
In short, the Perpetual Virginity of Mary will be a sign of God’s gracious love for her (and us) and of her (and our) total consecration to God—for Mary is, as St. Ambrose said, a “type of the Church”.
This is why the Catechism (paragraph 502) tells us:
The eyes of faith can discover in the context of the whole of Revelation the mysterious reasons why God in his saving plan wanted his Son to be born of a virgin. These reasons touch both on the person of Christ and his redemptive mission, and on the welcome Mary gave that mission on behalf of all men.
For Mary’s virginity bespeaks both God’s initiating power in salvation and the purity of her consecration to that saving act. Mary’s virginity shows that salvation is God’s idea, not ours, and that his saving act is due not to human desserts, but to the love of God that saves us despite our sinfulness. Salvation comes to us, “not of blood nor of the will of the flesh nor of the will of man, but of God” (John 1:13). The Virgin Birth (and therefore the Perpetual Virginity of Mary) stand as permanent testimony to that gracious act of salvation from God.
But it also stands as testimony of something else: the welcome Mary gave that grace (which was, itself, the fruit of grace). Mary’s virginity, like Christ’s is an image of total and pure self-offering. As the icon of the Church, she embodies the complete love and stainless beauty of the Bride of Christ just as he embodies the complete self-offering of the Bridegroom. The virginity of Mary, as the prophet Isaiah said, is the sign that in our Lord Emmanuel, God is with us.
The Fathers on the Perpetual Virginity of Mary
Let those, therefore, who deny that the Son is by nature from the Father and proper to his essence deny also that he took true human flesh from the ever-virgin Mary. – Athanasius
His [Christ’s] origin is different, but his [human] nature is the same. Human usage and custom were lacking, but by divine power a Virgin conceived, a Virgin bore, and Virgin she remained. – Pope St. Leo the Great
Early Protestants on the Perpetual Virginity of Mary
Christ, our Savior, was the real and natural fruit of Mary’s virginal womb . . . This was without the cooperation of a man, and she remained a virgin after that. – Martin Luther
Helvidius displayed excessive ignorance in concluding that Mary must have had many sons, because Christ’s “brothers” are sometimes mentioned. – John Calvin
I believe . . . he [Jesus Christ] was born of the blessed Virgin, who, as well after as she brought him forth, continued a pure and unspotted virgin. – John Wesley