We are grateful for Andrew Koppelman’s recent reply to our argument in the Harvard Journal of Law and Public Policy that marriage is the conjugal union of husband and wife. Thanks to his honesty and candor, the ensuing exchange should set in stark relief the implications of redefining civil marriage.

Professor Koppelman graciously credits our article with having “done [readers] a service with [a] succinct and clear exposition” of the arguments for conjugal marriage “that is accessible to the general reader.” Noting that “the most prominent response to [our] paper, by NYU Law Professor Kenji Yoshino, doesn’t really engage with any of [our] arguments,” Koppelman writes, “Here I will try to do better.”

Koppelman has indeed contributed importantly to the debate. Besides providing an opportunity for us to defend a core premise of our view, he has forthrightly admitted—he might say, embraced—the less politically palatable implications of rejecting our position.

Against our view that marriage is a pre-political form of relationship (albeit one that the state has compelling reasons to support and regulate), Koppelman holds that marriage is merely a social and legal construction—the pure product of conventions. Relatedly, he rejects the idea, long embodied in our law and the philosophical traditions supporting it, that spouses’ coition consummates marriage by sealing their commitment with a form of bodily communion made possible by their sexual-reproductive complementarity. And he acknowledges what we and he agree is an implication of his view: that there are no principled reasons for would-be spouses to pledge or observe permanence, sexual exclusivity, or monogamy.

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Koppelman’s concession on this important point is of more than merely academic interest. Consider the 2006 statement “Beyond Gay Marriage,” which endorsed “a new vision for securing governmental and private institutional recognition of diverse kinds of partnerships, households, kinship relationships and families,” including polyamorous (multiple “conjugal partner”) unions. Its 300 signatories—self-described lesbian, gay, bisexual, and transgender (LGBT) and allied activists, scholars, educators, writers, artists, lawyers, journalists, and community organizers—not only recognize that their rejection of sexual complementarity as essential to marriage abolishes any principled basis for monogamy and sexual exclusivity; they urge that the law reflect this, by extending recognition to polyamorous unions.

There is another, perhaps more surprising implication of Koppelman’s positing marriage as a pure social and legal construct: it undermines the evident views of many gay civil marriage proponents. For many on both sides of the debate argue as if marriage was not simply reducible to what the majority (through legal or social convention) says it is, but a human good with its own inherent requirements, which the state ought to recognize accordingly. For if there are no principled boundaries demarcating some intimate associations as marriages, then no principle requires holding that same-sex sexual partnerships are marriages. In that case, all it takes to justify traditional marriage law is that the non-recognition of same-sex partnerships offer some (or a net) social benefit.

Koppelman would deny that it does. But this re-invites the question: what is the net social benefit of excluding multiple-partner unions?

The social costs of recognizing polyamorous partnerships might include, say, increased administrative burdens for the state. But the benefits would presumably include spousal privileges, inheritance and hospital visitation rights, and in general more practical assistance to, and social acceptance of, the relationships that Americans in an estimated 500,000 polyamorous households find most personally desirable. The stigma against such people and their children would be weaker. They would feel less pressure to hide their romantic inclinations and lifestyle choices. Their economic situation could well be improved.

Recognizing the flimsiness of many marital norms if marriage is just a social construct, Calgary philosopher Elizabeth Brake has called for “minimal marriage,” in which “individuals can have legal marital relationships with more than one person, reciprocally or asymmetrically, themselves determining the sex and number of parties, the type of relationship involved, and which rights and responsibilities to exchange with each.” Koppelman presumably thinks it an injustice to fail to recognize relationships that are just as socially valuable as ones that we do recognize. So why isn’t Brake’s policy required in justice?

Of course, we believe that marriage is no mere social or legal construction, but a human good with certain inherent requirements that the state does not create but should recognize and support. Far from unique, marriage is in this respect like other moral realities, most notably human rights. The right not to be discriminated against based on one’s skin color, say, would exist as a moral principle governing human conduct even in the absence of positive law. Likewise, the inherent structure of the good of marriage exists, and defines the kind of commitment that would-be spouses must make if they wish to realize that good, even in the absence of marriage law. But what is marriage, so understood? That is the question to which we proposed an answer in the essay to which Koppelman responded. We turn now to his criticisms of our answer.

Bodily union: Does it matter? What does it mean?

We argued that marriage, as our law has historically recognized, is a union of persons along every dimension of their being. As such, marriage is uniquely embodied and sealed in the coition of husband and wife. Our law historically recognized that, too. For coitus alone unites spouses along the bodily dimension of their being and is, like the relationship that it seals, inherently oriented to procreation. Only such bodily union and its connection to children provide principled grounds for core marital norms (exclusivity, monogamy, a pledge of permanence) and make sense of the state’s interest in marriage over other personal bonds.

But Koppelman claims that “it is not clear that this kind of ‘organic bodily unity’ actually exists, or that even if it did, it would have the intrinsic value they attribute to it.” Now there are two ways to resist the view that the kind of bodily union possible only between a man and a woman has special value, and our article already includes replies to both.

First, someone might think that bodily union never has inherent value: emotional intimacy does, and sexual activity matters only when it serves that. Our article addresses this point:

Marriage is distinguished from every other form of friendship inasmuch as it is comprehensive. It involves a sharing of lives and resources, and a union of minds and wills… But on the conjugal view, it also includes organic bodily union. This is because the body is a real part of the person, not just his costume, vehicle, or property. Human beings are not properly understood as nonbodily persons—minds, ghosts, consciousnesses—that inhabit and use nonpersonal bodies. After all, if someone ruins your car, he vandalizes your property, but if he amputates your leg, he injures you. Because the body is an inherent part of the human person, there is a difference in kind between vandalism and violation; between destruction of property and mutilation of bodies.

Likewise, because our bodies are truly aspects of us as persons, any union of two people that did not involve organic bodily union would not be comprehensive—it would leave out an important part of each person’s being. Because persons are body-mind composites, a bodily union extends the relationship of two friends along an entirely new dimension of their being as persons. If two people want to unite in the comprehensive way proper to marriage, they must (among other things) unite organically—that is, in the bodily dimension of their being.

Second, some who see bodily union in marriage as inherently valuable and crucial may still think that any consensual sexual activity could realize it. Our article answers this view, too:

But what is it about sexual intercourse that makes it uniquely capable of creating bodily union? People’s bodies can touch and interact in all sorts of ways, so why does only sexual union make bodies in any significant sense “one flesh”?

Our organs—our heart and stomach, for example—are parts of one body because they are coordinated, along with other parts, for a common biological purpose of the whole: our biological life. It follows that for two individuals to unite organically, and thus bodily, their bodies must be coordinated for some biological purpose of the whole.

That sort of union is impossible in relation to functions such as digestion and circulation, for which the human individual is by nature sufficient. But individual adults are naturally incomplete with respect to one biological function: sexual reproduction. In coitus, but not in other forms of sexual contact, a man and a woman’s bodies coordinate by way of their sexual organs for the common biological purpose of reproduction. They perform the first step of the complex reproductive process. Thus, their bodies become, in a strong sense, one—they are biologically united, and do not merely rub together—in coitus (and only in coitus), similarly to the way in which one’s heart, lungs, and other organs form a unity: by coordinating for the biological good of the whole. In this case, the whole is made up of the man and woman as a couple, and the biological good of that whole is their reproduction.

Koppelman’s reply says nothing to address either of these points—that bodily union is necessary, or that only coitus effectuates it. He only cites a previous essay of his in which he argues that our view would exclude infertile couples. There he argued that a “sterile person’s genitals are no more suitable for generation than an unloaded gun is suitable for shooting. If someone points a gun at me and pulls the trigger, he exhibits the behavior which, as behavior, is suitable for shooting, but it still matters a lot whether the gun is loaded and whether he knows it.” But we had already responded to this objection in our new article, and his reply does not address our answer:

Natural organs and organic processes are unlike man-made objects and artificial processes, which retain their dynamism toward certain goals only so long as we use them for those goals—which in turn presupposes that we think them capable of actually realizing those goals. That is, the function of man-made objects and processes is imposed on them by the human beings who use them. Thus, a piece of metal becomes a knife—an artifact whose function is to cut—only when we intend to use it for cutting. When it is no longer capable of cutting and we no longer intend to use it for cutting, it is no longer really a knife.

The same does not hold for the union between a man and a woman’s human bodies, however, because natural organs are what they are (and thus have their natural dynamism toward certain functions) independently of what we intend to use them for and even of whether the function they serve can be brought to completion. Thus, in our example, a stomach remains a stomach—an organ whose natural function is to play a certain role in digestion—regardless of whether we intend it to be used that way and even of whether digestion will be successfully completed. Something analogous is true of sexual organs with respect to reproduction.

So bodily union matters to marriage, and only coitus achieves it (whether or not conception results). Koppelman says nothing to refute these points, or to address our answers to his previous objections to them.

He admits failing to see distinctive value in marriage so understood, and implies that few others can. On the contrary, our civilization (like others) has long recognized a human good with just these contours. Consistently and for centuries, our law (a) required coitus—and accepted no other act—for the consummation of any marriage, but (b) never treated infertility as an impediment to marriage. This cannot be ascribed to ignorance of infertility (the phenomenon was well known) or the difficulties of discovering it before a marriage: while non-consummation was treated as a ground for annulment or dissolution, infertility established after a wedding ceremony never was. Nor can this aspect of the legal tradition be ascribed to animus towards homosexuals or even the moral rejection of homosexuality: the law distinguished among possible sexual acts performed by the same legally wedded man and woman, and was settled in cases in which same-sex conduct or relationships were not at issue.

The only way to account for this longstanding legal practice is to posit something much like our view: people grasped (and in fact many still grasp) that comprehensive interpersonal union—permanent, exclusive, and sealed by coitus—is (a) valuable in itself and (b) distinguishable in principle from non-marital friendships and indeed every other inherently valuable human good.

Koppelman must find these features of historic marriage law to be baffling. Not seeing anything special in coitus or the kind of bodily union (and, therefore, comprehensive interpersonal union) that it makes possible, and unable to appeal to irrational motivations (like homophobia) or mundane explanations (like ignorance), he must find our legal tradition’s distinction between infertile opposite-sex couples and same-sex couples simply unintelligible. But it is perfectly intelligible the moment one recognizes that marriage is a distinctive form of relationship at once (1) inherently oriented to procreation, and (2) valuable in itself, and not as a mere means to procreation.

Just a legal convention?

In rejecting our argument, Koppelman also denies that marriage is a human good with certain inherent requirements that the state has strong reasons to recognize and reinforce. With admirable directness, he writes that marriage is “just a construct that has developed over time, and that therefore can be changed by human beings if that seems best.” To illustrate the point, he asks us to imagine a proposal to change one of the rules of chess:

I don’t think that this question can be resolved by trying to figure out what the essence of Chess is. Chess hasn’t got an essence. Doubtless the present game of chess was developed through just such fiddling; perhaps someone once thought that the drunken reel of the knight was hostile to the essence of Chess. The question is what sort of chess rules are likely, under the circumstances, to best realize the good of play.

Similarly, Koppelman suggests, there is no “essence” to marriage. For him, presumably, marriage laws are just so many contingent specifications of the highly varied good of intimacy.

Recall the fallacy in Koppelman’s objection to our view of infertile couples’ bodily union: that from the fact that guns (artifacts) lose their dynamism toward killing when they can no longer cause death, it would follow that our reproductive organs (natural objects) lose their orientation toward procreation when they can no longer cause conception. A similar fallacy would be needed to complete Koppelman’s argument up to this point: that from the fact that some social practices like chess are pure constructs, it would follow that that marriage is, too. But marriage isn’t a pure construct, any more than human rights are mere constructs. Both are moral realities that the state has good reasons to recognize and support.

But Koppelman has more to say. He seems to suggest that the concept of an independent basic good with certain pre-legal requirements is “barely comprehensible.” We can dispel this impression with another example.

Consider friendship. As with marriage, the particulars of friendship vary widely by time and place. But also like marriage, friendship is a human reality, a distinctive human good, with certain essential features independent of our social or linguistic practices. For example, it essentially involves each person’s actively willing the other’s good, for the other’s sake. And again like marriage, friendship (the human reality, not our use of the word) grounds certain moral privileges and obligations between its participants and even between the friends and others who might interact with them. So friendship, like marriage, is not just a social construct.

If we said that John and Joe, who just exploited each other, were not “real friends,” we would not just mean that a certain word did not apply to their bond, or that society failed to treat that bond as it does certain others. We would primarily mean that John and Joe were missing out on a distinctive, inherently valuable reality—a human good, for which other goods are no substitute—because of a failure to meet its inherent requirements, which are not purely socially constructed. Similarly, a relationship is not a marriage just because we speak and act as if it is, nor is a relationship not a marriage just because we fail to do so.

So it makes sense to speak of human goods with internal requirements that don’t just depend on linguistic or social conventions. And marriage between a man and a woman, we argue, is one of these goods. Koppelman gives no good argument for thinking that marriage is not, and people’s longstanding practices and understandings of marriage strongly suggest that it is. Koppelman cites shifting attitudes on these issues, confident that history is on his side. But we are confident that when Americans understand the implications of conceiving marriage as a mere social construct and legal convention, they will see the wisdom of preserving it as the conjugal union of husband and wife—and be reinforced in the view that it is so inherently.