In my previous post,Why the Catholic Church Defined Marriage,” I noted that the Roman pagan world, into which the Church was born, had monogamy, but not the Christian understanding of monogamy—and that’s why the Catholic Church had to properly define marriage 2000 years ago by redefining it against the pagan culture.

To repeat: Roman heterosexual monogamy was not life-long. The pagan Romans allowed easy, no-fault divorce, and multiple remarriages. A man had a right to have sex with concubines, his slaves (male and female, adult and child), and prostitutes. Marriage was basically a contract for having children and handing on property.

To be fair to the ancient pagans, there were a handful of Greek and Roman philosophers and statesman who proclaimed something much more like the Christian understanding of marriage—primarily Aristotle and the Stoics. But these philosophers were the exceptions, even among philosophers, and certainly had little effect on the larger culture—and it was that larger cultural, moral, legal context against which the Church redefined marriage as life-long, sexually-exclusive, heterosexual monogamy.

But if the Catholic Church redefined marriage once, can’t it redefine it again? That’s what proponents of gay marriage demand.

The answer is “no.” Redefinition is never possible again. The first redefinition 2000 years ago was a correction of the definition of marriage in light of revealed and natural truth, and these truths cannot be changed.

The corrected definition of marriage begins at the beginning of Scripture, but we generally don’t see its real depth. In Genesis, we find that the Creator of the world defined male and female as the pinnacle of creation, and this complementary pair together represents the image of God.

This is the revealed foundation of the Church’s redefinition of marriage as life-long, sexually-exclusive, heterosexual monogamy. Note that there are two elements to this understanding of heterosexual monogamy.

The first and most obvious is the natural, biological complementarity of one male and one female, the sexual union of which produces more human beings made in the image of God, male and female, boys and girls.

But it isn’t just bodily complementarity that defines marriage as heterosexual; it’s spiritual complementarity. The man has a male soul, the female has a female soul. The soul, as the Catechism states (365), isn’t a formless mist. The soul is the form of the body, and that means the form of either a male or female body.

This surprises us today. If we believe at all that we have souls, we tend to believe that we are androgynous ghosts stuck in gender-defined bodies. But that is actually a heresy—the heresy of the Gnostics who rejected the body as evil.

Given the creation of male and female, as presenting, in union, the image of God, we can understand why both the Jews and then later Christians understood men and women to be, in the marriage union, perfecting their full respective natures as male and female. For the Jews, a man could only be perfected as male in the spiritual-physical marital union with a woman; likewise, a woman could only be perfected as female in the spiritual-physical marital union with a man.

That’s the Old Testament Scriptural template for life-long, heterosexual, sexually exclusive monogamy. And that’s obviously a big part of the reason that the Catholic Church cannot redefine marriage ever again. It would simply have to deny the very beginning of divine revelation.

Now here someone might say, if that’s the beginning of the Old Testament, and it all leads to the Catholic definition of marriage, then why are the beloved and holy patriarchs polygamous? Why did Moses allow for divorce? Why does the barren Sarai say to Abram, “The LORD has kept me from having children. Go, sleep with my slave [i.e. Hagar]; perhaps I can build a family through her." And then Abram simply agreed to what Sarai said? Why does David, the archetype of the Messiah, have concubines?

The answer is that Genesis truly is the proper foundation for the Christian redefinition of marriage in regard to Judaism, and that’s why it took the Incarnation of Christ to clarify this natural and revealed foundation of marriage in Genesis even for the Jews. This is done by Jesus (Matthew 19) when He tells the Pharisees who had asked Him about the Law’s permission of divorce:

Haven’t you read that at the beginning the Creator ‘made them male and female,’ and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh’? So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate. … Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning. I tell you that anyone who divorces his wife, except for sexual immorality, and marries another woman commits adultery.

That is the full template for the Christian redefinition of marriage. Note that the monogamous sexual complementarity is essential to the union, defining it as “one flesh,” which excludes divorce and polygamy, but also a same-sex union. The biological complementarity of the sexual act of procreation as definitive makes it clear, through Jesus’s revealed, authoritative account, why the Catholic Church can never redefine marriage again. It can’t allow homosexual marriage, or divorce, or polygamy, or concubines, or sex with slaves, or immorality (i.e., adultery).

But revelation provides two other related reasons. We might not understand them if we think what Scripture tells us about the marital relationship between God and Israel, and then Christ and His Church, are nice illuminating metaphors rather than astounding revealed facts.

I should know, because that’s what I did for a very long time. I’d read Matthew 25, the parable of the ten foolish virgins who don’t prepare for the arrival of the bridegroom, and say to myself, isn’t that nice: Jesus is kind of like a bridegroom. Or I’d read John 3, where John the Baptist refers to himself as the friend of the bridegroom, and think to myself, isn’t that nice: Jesus is kind of like a bridegroom. Or I’d read Mark 2, where Jesus says, to the question of why His disciples don’t fast, "How can the guests of the bridegroom fast while he is with them? They cannot, so long as they have him with them,” and say to myself, isn’t that nice: Jesus is kind of like a bridegroom.

And then one day I got hit by a revelatory ton of bricks that whacked me hard enough to shatter the scales from my eyes. Jesus isn’t like a bridegroom. He is a bridegroom, the Bridegroom.

Just as suddenly, much of the Old Testament made a whole lot more sense, because God keeps referring to Israel as His Bride. That’s not a nice metaphor, I finally realized. Rather, the marriage union is the primary way that God reveals His covenant relationship to Israel in the Old Testament. That’s why the prophets continually identify idolatry as marital infidelity. And most importantly, I realized that Jesus is the fulfillment of that marital covenant relationship. Jesus is God-made-flesh; that’s why He IS the bridegroom.

Suddenly Ephesians 5 made a whole lot more sense because Christ IS the bridegroom and the Church IS the bride. Note the very strange but now very illuminating words of St. Paul, when He is telling husbands how they must act towards their wives, saying that husbands “ought to love their wives as their own bodies” so that husbands should “feed and care for their body, just as Christ does the church—for we are members of His body.”

And then St. Paul gives us the big revelation: “‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.’ This is a profound mystery—but I am talking about Christ and the church.”  

The Bridegroom and Bride imagery that describes the intimate relationship of Christ to His Church is NOT imagery, not mere metaphor, but a profound mystery (the word mystery in Greek being the word for sacrament). Christ forever defined His intimate relationship to the Church in terms of life-long, exclusive, heterosexual monogamy.

That means that the “one body” or “one flesh” of the natural marital union is an image of the “One Body of Christ” that is the union of Christ with His Church. The Church cannot redefine marriage, because marriage itself is defined in terms of Jesus Christ and His Church, a revealed mystery that must be accepted as Divinely ordained.

Marriage between a man and a woman is thus defined in terms of our nature as one male and one female in union, and as a mystery itself, a sacrament, a reflection of the enduring sacrificial love that Jesus Christ, the bridegroom, has for His Church, the bride.

To redefine marriage now—as many are demanding of the Church—would therefore go directly against the order of nature, and against the order of redemption established in Jesus Christ. It cannot be redefined without destroying those divinely ordained orders.