Why do the advocates of same-sex marriage want what they want? And why do defenders of traditional marriage, as uniting men with women to form families, resist such a change? One cannot do better for achieving clarity on such questions than by reading Debating Same-Sex Marriage, co-authored by John Corvino and Maggie Gallagher. Corvino, who teaches philosophy at Wayne State University in Michigan, and Gallagher, a co-founder of the National Organization for Marriage, have achieved something of real value in this book, confronting one another with (in general) an admirable degree of civility. Given the space to build arguments for their own views, and to respond to each other at length, Corvino and Gallagher provide what are probably the best and the most complete arguments on either side of this momentous debate.

And this is why Debating Same-Sex Marriage so admirably exposes the weakness of the case in its favor.

Gallagher sums up the aims of the two sides this way:

For gay marriage advocates, the ultimate end is equality: the recognition of gay unions as marriages in all fifty states and ultimately around the world as part of the process of creating a world in which sexual orientation is treated like race.

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For opponents of gay marriage, stopping gay marriage is not victory, it is only a necessary step to the ultimate victory: the strengthening of a culture of marriage that successfully connects sex, love, children, and mothers and fathers.

Corvino no doubt agrees with Gallagher’s characterization of his side’s argument. What he gives no credence is her account of her own side. Indeed, he signally fails even to grasp the kinds of arguments Gallagher makes, and then concludes, from his own failure, that her arguments must be incoherent. But the shoe is on the other foot.

The trouble for Corvino begins with the tissue-thin brevity of the positive case he makes for “marriage equality,” as he calls it. In a mere eight pages or so—constituting just a tenth of his opening “case for same-sex marriage”—Corvino tells us that marriage, more than any other arrangement or institution in which two people can take part, “promotes mutual lifelong caregiving.” This, he would have us believe, is the core, the irreducible purpose of marriage, its true raison d’être. Some homosexual couples really want to enter into such an arrangement, and to have it called “marriage” under the law with all the attendant rights and recognition that accompany the label. For Corvino, their desire for this recognized arrangement supplies them with a presumptive right to it, in the name of equality. And so for the remainder of his main statement, and his reply to Gallagher’s statement, Corvino devotes all his space to attempted rebuttals of the opposing view.

That is, he proceeds as though the common understanding of marriage advanced by every known civilization must justify itself before the tribunal of a wholly new and unproven understanding. And this sets the pattern: Corvino alternates between ineffectual logic-chopping that evades the real issues regarding the nature and purpose of marriage, and making the argumentum ad misericordiam, the appeal to our sympathy for gay and lesbian couples. If only we understood how important it is to this or that couple to be able to marry, we would drop our objections. We would understand that “to deny marriage to a group of people” who want it very badly is to tell them that “you are less than a full citizen.”

But as Gallagher shows, the reason marriage exists in the first place is not to satisfy the longings of any two (or more) persons for social recognition of their desire to care for one another for the long haul, or to make anyone feel better about his place in society. The reason marriage exists is because (in the briefest version of her argument), “sex makes babies, society needs babies, children need mothers and fathers.” These are, she rightly notes, social problems for which marriage is the institutional solution. Our private relationships are generally none of the state’s proper business. But society’s manifest need to regulate procreation and the responsibility for children elevates marriage—and the legitimate family relations that flow from it—from the plane of private law to the plane of public law. As the family of mother, father, and children is more basic and natural than the state, so marriage, as the relationship that founds the family, needs and deserves all the status the state can bestow upon it.

What problem, by contrast, does same-sex marriage solve? No two persons of the same sex can, without the aid of others, generate children. Again, the best Corvino can offer is that “it’s good for people to have a special someone” and that “commitment matters.” True enough. But these are not, even remotely, social problems requiring an institutional solution. Marriage, for same-sex couples, is a solution in search of a problem.

Yet it is more than that, for, as Gallagher also demonstrates, same-sex marriage promises to create all sorts of new problems, and to exacerbate others we already know. Marriage in the modern age is a wounded institution, and the advent of same-sex marriage would injure it further. We already have trouble remembering that marriage is about procreation—and that procreation ought to take place within marriage. Same-sex marriage would make remembering this harder. We already have trouble honoring fidelity, exclusivity, and permanence in marriage; same-sex marriage would make this harder too. We already have trouble articulating why our society rejects polygamy, or even incest; same-sex marriage would render us speechless. We already have trouble recalling that marriage unites men and women so that children have both mothers and fathers, preferably the ones nature gave them; same-sex marriage means actively rejecting this idea. And this rejection begins with the necessity of telling ourselves a lie about what marriage is, a falsehood that is wrong in itself and that has terrible fallout.

To all of Gallagher’s deep reflections on the nature of fundamental human relationships, Corvino can only reply with shallow recourse to mere conventionalism. Marriage, he argues, is an evolving social institution, which has picked up new baggage and shed old baggage over the centuries. It is simply a name we give to our most highly prized relationships of mutual care and commitment. Therefore, if we decide to include same-sex unions among such relationships, all we are doing is changing the “established usage” of the word. Marriage is, for Corvino, like other entirely conventional institutions with meanings that utterly “depend on shared understanding across a community,” like “corporation” or “baseball.” In a world in which the word “mother” has as much connection to nature as the phrase “designated hitter,” the purblind philosopher is king. As Gallagher writes, “an institution with deep roots in human nature and human necessity becomes contingent and arbitrary, a product of will and politics, as the rational connections between its component parts are severed.”

There is much more coverage of the controversy over marriage in this book than a brief review can recapitulate, including a discussion of the social science on same-sex parenting that has been overtaken by the recent research of sociologist Mark Regnerus and the New Family Structures Study (about which, see recent Public Discourse articles here and here). But there is one respect in which Corvino’s contribution to Debating Same-Sex Marriage is truly hair-raising. When Gallagher argues that one of the essential meanings of same-sex marriage is that it will result in the privatization and stigmatization of beliefs about marriage that have prevailed in every age and culture, and the active suppression of such beliefs in the public square, Corvino concedes that this is so. He replies, with an honesty that is both commendable and chilling: “Whichever side prevails in this debate, the other’s views will be marginalized. There’s no getting around that.”

In other words, Corvino does indeed look forward to a future in which those who believe men can only marry women and women can only marry men will be treated as bigots, just as racists are treated today. In this future, already working itself out in states and countries with same-sex marriage (and even some that so far have only same-sex civil unions), these bigots will be denied advancement in their professions; their rights to conduct private businesses according to their view of the reality of marriage will be regulated out of existence; their children will be inculcated with a view of marriage that is anathema to them; and in general they can look forward to being told they are in the grip of an “irrational hatred” they must relinquish as an obsolete social pathology. The fact that considered moral views, and not animosity, are at the root of their beliefs, will matter not at all. The fact that, for most people believing what human civilizations have always believed about marriage, this belief is intimately bound up with religious faith and vouchsafed to them by revelation itself, will avail them nothing.

A future in which same-sex marriage is enshrined in the law is a future without meaningful religious liberty, freedom of speech, or economic freedom for millions of Americans. Yes, they can “privatize” their view, and go about their business incognito, as it were. But that is a surrender of their freedom, not a preservation of it. As Gallagher astutely notes:

Using the power of law and culture to suppress alternative conceptions of marriage and sex (because gay people find these ideas hurtful and insulting to the newly internalized equality norm) is not a bug in the gay marriage system, it’s a feature. It’s part of, if not the main point.

Corvino is right. One side or the other will have its view “marginalized.” Until just a few years ago, the notion that persons of the same sex could marry one another was the very definition of a “marginal” view. Practically no one took it seriously, even among gays and lesbians (who do not universally embrace it even now). The case in its favor is so undeniably weak, as Corvino’s contributions to this book demonstrate, that the progress the same-sex marriage “movement” has made is an amazing tale of the incantatory power of the word “equality.” When the incantation fades, and sense returns to those who have been bewitched by it, the idea of same-sex marriage will once again retreat to the margins of society. That will be a victory of justice over tyranny. The only question is, will we resist the disastrous error of an experiment with a lie, or will we try to live the lie and then have to recover from it? Human societies have experimented with lies before. It is better to avoid them in the first place.