As a Catholic I believe that Mary was Ever-Virgin. However, I have always wondered how Mary could have been married if she was a virgin. My understanding was that sexual intercourse completed the sacrament of marriage. A First Things article concludes that Mary was indeed a virgin and yet truly married to Joseph. This article (below) is the best I can find addressing the issue.
Were Joseph and Mary married? The Catholic Church, Eastern Orthodox, and some Protestants teach that Mary remained “ever virgin.” Some, though, claim that a marriage has to be consummated to constitute a real marriage. Is this true? And what is the Church’s position on such marriages today?
Under Roman law of their time, Mary and Joseph were clearly married. Nuptias non concubitus, sed consensus facit (It is not sleeping together, but agreement that makes marriage), wrote the prominent Roman jurist Ulpian (170-228). In his famous letter written to the Bulgarian prince Boris I in 866, Pope Nicholas I takes the same view, “according to the laws (leges), the consent of those whose union is arranged should be sufficient. If that alone is absent, all the other solemnities, even including coition, are in vain, as the great teacher John Chrysostom attests, who says: Not intercourse but will makes marriage.”
Yet the declaration from the book of Genesis, “and they shall be one flesh,” suggests that consummation is essential to marriage. That is what the great canonist, Gratian of Bologna thought in the twelfth century. However, Peter Lombard thought otherwise, insisting that it was the agreement, the meeting of minds of the couple that makes marriage, leading to a lively debate between the universities of Bologna and Paris.
The Parisian view was adopted by Pope Alexander III (1159-1181) in answering a case propounded to him by the Archbishop of Salerno, declared that if consent depraesenti (“de præsenti” is an ellipsis for “de præsenti tempore”—“words in the present tense”) was expressed by such words as these “I accept you as mine.” “and I accept you as mine”, whether an oath was interponed or not it was unlawful for the woman to marry another and if she should contract a second engagement by promise even although followed by sexual intercourse she should be separated from the second and should return to the first husband. [Corpus Juris Canonici Decretales Gregory IX lib iv tit iv cap iii] Alexander III confirmed the Parisian view in another decretal, “Veniens ad nos G.”
And what of Genesis? The Parisian school countered with First Corinthians: “The wife hath not power of her own body, but the husband: and likewise also the husband hath not power of his own body, but the wife.” From the moment of the marriage the man has no power over his own body. His body is already his wife’s and her body is his. Therefore, this is the moment at which they become “one flesh.” Their agreement makes them “one flesh” by giving to each power over the other’s body; the sexual union is mere matter of fact. As the great English legal historian, F W Maitland put it, “We must distinguish between the perfection of a legal act and the fulfillment of obligations which that act creates.”
Alexander III, following the ancient tradition of the Church declared that “After a lawfully accorded consent affecting the present, it is allowed to one of the parties, even against the will of the other, to choose a monastery (just as certain saints have been called from marriage), provided that carnal intercourse shall not have taken place between them; and it is allowed to the one who is left to proceed to a second marriage.” [III Decretal., xxxii, 2] but this is a case of the dissolution of a marriage, not a declaration that there was no marriage to dissolve. The Council of Trent makes this clear: “If anyone shall say that a marriage contracted, but not consummated, is not dissolved by the solemn religious profession of either one of the parties to the marriage, let him be anathema.” [Sess XXIV Can vi) In Maitland’s words, “a marriage is a marriage, and it cannot become more of a marriage than it already is.”
The answer, then, is yes. Whether viewed in light of Church law today or of Roman law of their own time, Joseph and Mary were fully and truly married.