If, as G. K. Chesterton said, tradition is the democracy of the dead, then one can understand how someone might think of progress as the democracy of the future. That seems to be how many journalists and politicians are understanding progress when they talk about opponents of same-sex marriage being on the “wrong side of history.” Of course we can never be as sure of what most people will think in the future as we are of what most people have thought in the past. For the past, the vote is in. For the future, we have only extrapolations based on trends—in this case, surveys showing that young people are more likely than their elders to suppport same-sex marriage.

But just as a working democracy does not accommodate the opinions of the dead in its procedures, neither should it pretend to speak on behalf of future generations. A self-governed people must accept the burden of speaking only for themselves, only for now. We may think of posterity when we form our own opinions, but we cannot think for it and, just as important, it cannot think for us. If modesty doesn’t prevent us from pretending to speak for the future, historical awareness should. (Eugenics was once supposed to be a historical inevitability, until, after the Second World War, suddenly it wasn’t. Who knows? Perhaps it will get a second chance. Some future generation may decide that we overreacted to the ugly idea of Lebensunwertes Leben.) But we can speak only from where we stand. When we pretend to speak from farther down the road of history, we are only throwing our voices. Appeals to History’s moral authority are formally no different from appeals to divine authority: they both involve claiming some transcedent warrant for one’s position. The difference is that those who appeal to divine authority know and say that’s what they’re doing, while those who appeal to a speculative future insist they are merely looking at the hard data of opinion surveys and responding pragmatically.

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If History cannot settle such a controversy for us, neither can the Constitution. Pretending it does is just another kind of ventriloquism. The Constitution gives us only the framework we need to settle such controversies for ourselves—until, that is, we settle them again differently sometime in the future. In a well-functioning democracy, there is no once and for all.

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If it is OK for an advocate of same-sex marriage to make this kind of argument now, then it was OK for opponents of same-sex marriage to anticipate this kind of argument before—and not OK for anyone to mock them for doing so.

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In traditional Catholic moral teaching, homosexuality was understood to be a kind of vice. But why do so many Catholics seem so much more concerned with sexual vice than with all the other vices? One obvious answer is that Catholics have no choice: they seem preoccupied with sex only because their church’s sexual teachings are the part of their tradition most at odds with the secular culture of this particular time and place; Catholics’ apparent obsession with sex is just a function of this contrast.

Nevertheless, it’s hard to argue that our culture has a much bigger problem with lust than with greed or gluttony. Of course, sex is important, for reasons evident to everyone, but the church’s position has always been that, however important it may be, it isn’t necessary: one can live a good life, a full life, without it. Christian ascetics forewent the pseudo-immortality that sex and offspring offer because they had the real thing, the promise of eternal life. For most of the church’s history, what was most distinctive about Christian sexual morality was not its condemnation of sodomy or contraception, but its non-cultic celebration of virginity and what we might call its preferential option for celibacy. Notwithstanding the divine injunction to be fruitful and multiply—an injunction understood as a general imperative by Jews and, later, by many Protestants—the original Evangelical message was that you were to do without sex if you possibly could. The highest vocations, the most heroic holiness, excluded sex. This was true of no other object of natural appetite. The Christian ascetic fasted, but he also sometimes ate and drank; he slept less, but he slept. Sex he gave up altogether, because he could, and because he considered sex to be, at best, a distraction.

Now many popularizers of the Theology of the Body sound like a supernaturalized D. H. Lawrence. They have turned the satisfaction of a natural appetite, a common pleasure, into an esoteric rite, to be savored most fully only by those familiar with Trinitarian theology. In fact, early Christians were a lot closer to Tolstoy’s The Kreutzer Sonata than to Lady Chatterley’s Lover.

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But what if those early Christians were wrong? Maybe their distrust of desire as concupiscence was excessive and unnatural. Maybe their Evangelical witness—joyfully forgoing the goods in this life in pursuit of those in the next—soon curdled into an unhuman contempt for pleasure. Many people thought so at the time, and many think so now. Sexual desire, like hunger and thirst, is a natural appetite, a part of our animal nature. Only, unlike hunger and thirst and every other animal appetite, it does not correspond to a biological need of any individual animal, but only to the need of the species to perpetuate itself. The human race cannot survive without sex, but a human being can. Maybe this is why some ancient Christians were tempted to think of sex as a kind of luxury—an unnecessary and therefore artificial desire. If so, they were wrong. It is no less natural for being (personally) unnecessary, no less natural than eating and drinking. That being the case, why speak as if sex can be theologically rationalized only by turning it into a pale representation of supernatural realities? That doesn’t sit well with ordinary experience. If the pleasures of the flesh—by which we usually mean one pleasure in particular—are only presentable in mystical disguise, then we should distrust them the way St. Augustine did. But if that pleasure of the flesh is no more suspect than any other—and the desire for sex no more connected to sin than hunger or thirst—then why not take our D. H. Lawrence neat rather than watering down a natural pleasure with pious obscurantism? The tension in our own tradition remains unresolved.

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Today, when we talk about marriage, we talk about recognizing the intimacy between two people. But when we talk about divorce, suddenly marriage becomes just another dispensable legal arrangement. As long as we want it, marriage is whatever we want it to be, a projection of our deepest, truest selves. As soon as we want to be free of it, it becomes an inflexible institution totally at odds with our truest, deepest selves. We fall in love and get married. But it fails. It doesn’t work out. In retrospect, what we had described as a commitment becomes simply a failed experiment. The pain of divorce may be as great as the joy of marriage, but for the former we demand only complete privacy, for the latter public recognition.

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If marriage is now about celebrating the love between two people rather than solemnizing a vow that involves the intention to be fruitful and multiply, then what possible objection can there be to same-sex marriage? Who will deny that people of the same sex can love each other as much as people of the opposite sex? As many on both sides of this issue have observed, the traditionalists lost the political debate over same-sex marriage a long time ago, before most of us knew it had even begun. The meaning of marriage has been changing for decades, even though we’re only now getting around to changing the formal definition.

The best nonsectarian arguments against extending civil marriage to gays and lesbians have insisted on the importance of marriage to children: it is the state’s interest in the welfare of children, we are told, that gives it a reason to involve itself in what might otherwise appear to be an entirely private matter. Children do best, say opponents of same-sex marriage, when they grow up in a home where they have both a mother and a father. That—and not just the obvious biological fact that it takes one man and one woman to conceive a child—is the rationale for the traditional definition of marriage.

But this is also an argument against no-fault divorce, and while some opponents of same-sex marriage may quietly acknowledge that we’d be better off without that too, they have no illusions about using the law to enforce the indissolubility of marriage vows. Insofar as it is true that divorce is usually bad for children (a disputed claim), we have already decided that the state should give the liberty and privacy of adults more weight than the psychological welfare of children. If the battle against same-sex marriage, then, is not so much about sexual morality as about child welfare, then those who are fighting this battle must do a better job of explaining why this is where they’ve chosen to take their stand. (They can no longer say it’s about probability of success.)

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But I agree with the opponents of same-sex marriage: the state’s interest in marriage is principally about its interest in the welfare of children. Which is why it should stop regulating marriage and instead worry only about parenthood. Let the state concern itself with any household where children are being raised and leave sexual relationships to take care of themselves. For all other practical purposes—for hospital-visitation rights, pensions, etc.—civil unions are sufficient, not only for gay and straight couples, but also for a couple of friends or siblings who share a home. Here sex is irrelevant. The only thing civil unions need to have in common with marriage is the number two.

Of course, people will continue to get married, in their churches or in their backyards. Some of them—for example, Catholics—will believe they are partaking in a sacrament, promising themselves to each other before God. Others will believe they are making a solemn vow only before their friends and family. Some will be celebrating a relationship that already has more years behind it than ahead of it. Some will be saying, “Till death do us part,” while others will prefer less demanding vows. Some will understand fidelity to mean exclusive commitment, but others will prefer a marriage that is “monogamish.” Some will still marry to have children, but others will see the decision to have children as separate from the decision to marry. In short, marriage will mean different things to different people, because it already does. It is not necessary—and may no longer be possible—for the state to get them all to agree.