In previous articles, I have asserted that if sex did not naturally lead to children, no one would ever have conceived the idea of marriage. My claim may be obvious to most people, but we live in a world in which people who never intend to have children get married; so, of course, do some people who want children but are infertile. In generations past, we felt compassion for those who married but did not have children, because it was presumed that they wanted children, since, after all, they married one another. No longer can we presume this. The era of contraception and surgical sterilization has altered the face, so to speak, of the childless couple, and consequently the face of the married couple.

The quest for same-sex marriage begins here. In a world where seeking marriage is seeking a community-endorsed way to have sex and bear children, the idea of same-sex marriage is like the idea of a square circle. The very idea of same-sex marriage is conceivable only in a world that is using the term “marriage” in a completely different way, to refer to something of a completely different nature.

Allow me, then, to make a case for my assertion about sex, children, and marriage through a “thought experiment”—a scenario in which human beings have no word for, no concept of, marriage.

Imagine a colony of young men who have no memory of ever having lived anywhere else. Properly speaking, the men do not even know that they are men, but only that they are different from all the other creatures they encounter. They hunt and gather. They are naturally social beings who care about each other, form friendships, try to please one another, generally live according to the rules, and have formulated various rites of initiation, celebration, and grief concerning the important moments of community life. These social beings find that certain things they do for one another cause pleasure, both physical and emotional. They tend to each other, rub each other’s feet when they are sore from the long hunt, hold and caress each other in times of sorrow and illness.

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One day, two of the men announce that they are very special friends, because they really like each other’s company, help each other to be better, and they give each other especially good foot rubs. The members of the community are, of course, glad for them: friendships are important, and they all know the pleasures of a good foot rub between friends. These two, however, want to go further: they want to move off to a separate hut together, so they can experience their foot rubbing in private. They also wish to pool together their worldly resources, and to promise before the entire community that they will rub only each other’s feet until they die.

Though jaws have dropped, the pair is not finished. They want the community to validate the joining of their lives in this way, support them in their choice, and help them to remain faithful in their foot-rubbing exclusivity when they are tempted to do otherwise. They want a special ceremony to initiate their combined lives. But the community refuses: What is so important about close friendship and foot rubs that we need to form a special rite to acknowledge it? Do you really want us to force you to remain friends when things go sour? There is nothing in either friendship or the mutual giving of pleasure that requires the community’s input.

Now, the idea that any pair of these men would choose publicly endorsed exclusivity for enjoying the pleasures and closeness of foot rubbing sounds unlikely, even absurd. Nothing is enhanced for the pair of men by such exclusive activities, and there is nothing in it for the community to be bothered with.

Even had these men instead discovered (what we call) sexual pleasure, which is obviously more intense and more conducive to bonding than the best of foot rubs—and at times surprisingly urgent—the logic would remain the same: what they have discovered is an act which is very pleasurable, and which may help to strengthen friendships and express affection. But the same goes for back-scratching, being on a team, or working together on a project. There is nothing in this kind of act that would recommend exclusive relationships, let alone special community recognition.

Eventually, some bright fellow with philosophical leanings in the colony asks the question: What are these feelings for? Why the urgency? The leaders who first brought the men to the colony reply: “The answer lies over the mountains.” Those who want to find an answer begin their journey.

Over these mountains, there is a colony of young women. For their part, they know only women, though they do not know they are women, properly speaking. They gather and cultivate. Since they, like the men, are naturally social beings who care about each other, they also form friendships and have important religious and community ceremonies to mark important moments. They too find similar things useful, pleasurable, and comforting—including what we might call “sexual” pleasuring. So they do those things that are useful, comforting, affirming, caring, and pleasant.

Like the men—yet quite unlike the men—the women have parts of their bodies about which they cannot quite make sense. Why does our body do this? What is this longing all about? They are told: “Wait. The answer will come from over the mountains.”

Imagine the surprise when these two groups finally meet. Here are beings who, unlike any other creature on earth, but just like us, talk to one another, are intelligent, walk upright, gather things, build things, grow things, live in deliberate communities with rules. Yet they are so unlike us; their bodies are quite different in several obvious ways.

You can imagine that it would not take long for some enterprising couple to find the answer to their urges and longings in each other. Best of all, some of those peculiar organs fit together in an intensely pleasurable way. This does not mean that everyone in these two communities takes to this new kind of man-woman pleasure. Some are quite comfortable sticking with what they have always done; some men find the women, and some women find the men, too strange, too foreign to share this kind of intimacy. And so they continue in their old habits.

Despite the introduction of this new twist in giving pleasure and becoming closer as friends, the community has been presented with nothing qualitatively different from the status quo ante. They have discovered a new way of bringing pleasure. But ultimately, they can see no real difference between what they used to do in their isolated colonies, and what they now do in the mixed one. Neither the individual men and women, nor the community, is presented with any reason to treat these couplings as anything more than pleasure-inducing, friendship-building activities, like foot rubs or back scratches, playing games or working together.

But when, nine months later, the first baby is born, and the first mother nurses it, and the first father seeks to protect them both and care for them, the entire community would have a moment of recognition: So this is what these urges and these bodies are for!

Under these conditions, it would make sense for the whole community, and its individual members, to recognize this momentous event for what it is. From these bodies, male and female, through this act, a child is brought forth into the world—a child who needs to be protected, nourished, and taught. The community now has a reason to say several things: First, this act that we men and women have been doing together is an act that has extraordinary consequences for the whole community—consequences that our acts alone or in the previously isolated communities did not have. Second, it has extraordinary implications for the couple who have received both a gift for which they yearn to care, and a grave responsibility. Third, it has serious implications for the child, who finds herself born into the world, in need of care, education, and the security of knowing who she is, where she comes from, and where she is going. Fourth, now that they see what their bodies and urges are for, the members of the community understand that their earlier acts were in fact an improper use of their bodies and a misplacement of their longings (though none of this was their fault, given the incompleteness of their information).

Thus, it is in the interest of the community, the couple, and most especially the child that human sexuality be protected and nurtured such that it will be used aright. For this reason, entering into a sexual relationship with a member of the opposite sex is a matter of great importance for the community and the couple, worthy of a rite of recognition and acceptance, of being made secure in and by the community, and of rules governing their sexual practice. It is only here that the notion of marriage can be brought forth—not from the desires of the couple for recognition, not from feelings of affection and closeness, but in the face of the reality of human sexuality.

Of course, this story is a thought experiment, not history. It illustrates that it is within the realm of human experience for human beings to form bonds of friendship that are centered in, and enhanced by, mutually pleasant acts. But it also illustrates the unreasonableness of the notion of marriage in a world where a pleasurable act cannot, by its nature, lead to children; in other words, it shows the unreasonableness of marriage being merely about the desires, pleasures, and affirmation of adults—the contemporary conception of marriage.

A contemporary characterization of marriage looks like this: (1) two people (2) with great affection for each other (including, generally, desires for deeper knowledge, interpersonal closeness, and mutual care) (3) also want to have sex together, so (4) they consent to combine their lives materially and economically, and (5) to have sex only with each other, (6) with the ritual recognition, endorsement, and support (often material) of the community. Since same-sex couples can meet the first five criteria as easily as opposite-sex couples, how can society refuse the sixth? If the list above fully describes the proper relationship between sex and marriage—sex is just a deeper expression of personal affection and friendship, and marriage is an arrangement concerned with nothing more than this—then we must acknowledge that same-sex couples are just as capable of marriage as opposite-sex couples.

But this is where it must be pointed out that the act in which opposite-sex couples wish to engage has a very public outcome: children. Let me put my initial assertion another way: if sexual intercourse between a man and a woman always and naturally led to the same outcome as genital contact between two people of the same sex—that is, pleasure, increased feelings of closeness, even affirmation and love, and nothing else—no one would ever have come up with the idea of marriage.

The best that can be said about the contemporary face of “marriage”—the deliberately childless union, or union built around the desires of adults, with children a secondary and dispensable characteristic—is that it is entirely parasitic on the proper idea of marriage. Impossible to imagine on its own, it takes real marriage and strips it of the thing that gives it meaning, yet continues to refer to it by the same name. That means that the notion of “same-sex marriage,” which relies entirely for its conceivability on the notion that marriage exists for the desires of adults, is by that fact two levels removed from reasonableness.