Recently in Public Discourse, Francis Beckwith argued that the frequently invoked analogy between same-sex marriage and interracial marriage is flawed, and should not be used by advocates for the legal recognition of same-sex unions. As Beckwith wrote, this analogy is freighted with enormous moral and intellectual force, but it does not withstand examination. Bans on interracial marriage are not relevantly similar to current marriage law with respect to homosexuality. Professor Beckwith specifically points out that bans on interracial marriage attempted to revise centuries of common law that had always allowed persons of different races to marry one another. Legal bans on the practice merely made illegal actions that had once been legal (and remained legal except in the few polities that enacted such bans), and which everyone understood to be possible by nature. This is an important difference from the current argument about the legal recognition of same-sex unions, which revolves in part around whether it is in fact possible for two people of the same sex to be married to each other. Professor Beckwith does not address another difference, one possibly even more important because it undermines the moral force of the analogy: bans on interracial marriage were formally discriminatory. Existing marriage law is not.

What I mean by formal discrimination is that laws banning interracial marriage explicitly banned interracial marriage. Those who sought to overturn these bans were seeking formal equality: not the addition of more laws to include them, but the subtraction of laws designed to exclude them. What they wanted was for race not to be mentioned in the law at all. By contrast, what proponents of same-sex marriage seek is a different kind of equality. They want the law to say that homosexuals should get to marry the kind of people they desire. Their claim might be right, but it is important to note that the law does not currently say “only heterosexuals get to marry the kind of people they desire.” The law makes no mention of heterosexuality at all, a concept that would have been foreign to the originators of current marriage law.

This is why opponents of the legal recognition of same-sex unions sometimes note that homosexual persons are already free to marry, so long as they marry someone of the opposite sex. It is understandable that this point strikes many as a bit glib, and no doubt it is sometimes meant to be. It underscores, however, the essential disanology between anti-miscegenation laws and current marriage law: proponents of same-sex marriage do not propose to extend an existing liberty to a broader class of people, but rather to change the nature of an existing legal institution to which all people, qua people, already have access.

Race and homosexuality do have an important characteristic in common. While the underlying trait that they identify (variation in skin color and ongoing sexual desire for individuals of the same sex, respectively), may have always existed, the people who have the trait were not always seen as forming a natural class. Both race and homosexuality are historical concepts that arose at a particular period in history. With respect to race, while people have probably always noted that human skin can be shaded in a wide variety of ways, it was not until the early modern period that anyone began to speak not merely of peoples constituted by ethnic, linguistic, or cultural similarities but of a much broader classification of all the world’s people into categories based on skin color. The trait itself did not suddenly become more pronounced—if anything, it is likely that in the early modern period shades of human skin around the world were growing less distinct as contact between geographically distant peoples became more common. Rather, for purely extraneous reasons, very probably economic reasons relating to the slave trade, a broadly shared understanding arose that individuals who shared the trait of dark or light skin color with others could be grouped with those others into a class. Roughly the same process occurred, though much later, with homosexuality. The idea that the human species is divided into classes of persons who permanently desire members of the same sex and persons who permanently desire members of the opposite sex is recent, and many of those responsible for creating this idea used it as a way of medicalizing or marginalizing the individuals newly singled out as “homosexuals.”

Start your day with Public Discourse

Sign up and get our daily essays sent straight to your inbox.

Only if this idea is already accepted could current marriage law even conceivably be called exclusionary of homosexuals specifically. It is very probable, for instance, that many individuals, whether because of their genes or some environmental factor, experience an unchosen and insurmountable sexual desire for children or animals. Some people claim to be oriented to desire objects, and others to desire multiple partners as a matter of basic fulfillment of their sexuality. Others may feel persistent and unchosen desires for specific sexual acts to the exclusion of others. It is likely that many fetishists experience their desires for a particular kind of sex as permanent and unchosen. Human sexuality is not by nature divided into two symmetrical orientations. If you examine it without reference to the particular categories we now employ, the diversity, or perversity if you wish, of human sexuality, appears limitless. Just as the skin colors of different races flow continuously into one another, there is an infinity of difference in modes of sexual desire and sexual practice. (This is not to say that normative distinctions cannot be made between different sexual practices, of course.)

More importantly, many societies do not understand certain traits of sexual desire to constitute a kind of person at all. Even if it did turn out, improbably, that all human populations were neatly divided into people who desire members of the same sex and those who desire members of the opposite sex, this fact would not alone give us a reason to view “homosexual” and “heterosexual” as natural classes of human beings. Many traits do in fact divide human beings into discrete categories, but we do not see these different categories as giving rise to categories of persons. For instance, there exists a set of individual humans with birthmarks on their left legs. Our society does not have a name for this set. They are not spoken about as having a common set of aspirations or goals, or a common set of characteristics beyond their collective spottedness. Even though ever human population is divided without overlap into two discrete categories based on the spottedness of left legs, we do not understand this fact to create two natural classes of human beings.

Societies do categorize people, of course, and frequently change how they categorize people. Just because our society recently changed its categories to reflect a somewhat arbitrarily drawn difference along a particular axis of sexual desire does not mean that it was wrong to do so. However, our current marriage law was created long before the concept of homosexuality. Its authors could not have dreamed that the institution of marriage excluded a class of people. They probably did understand that the institution did not accommodate all relationships, but proponents of same-sex marriage do not advocate for the universal recognition of all relationships, as this would of course mean the end of marriage as an institution designed to pick out a certain type of inter-personal relationship from among the enormous range of relationships that exist. No one proposes special state recognition of the momentary relationships created by business transactions, nor even more the more permanent relationships of friendship.

By contrast, exclusion of a certain class of people is the whole point of laws banning interracial marriage. Anti-miscegenation laws relied extensively on the concept of race. In fact, the first clauses of the statute overturned by Loving v. Virginia were concerned primarily with establishing on a legal basis the categorization of citizens by race. Whether or not you believed in the category of race, and whether or not the category of race was meaningless or not, the statute either included or excluded you.

Current marriage law excludes no one in this way. Current law recognizes a certain kind of relationship and denies no one access to this recognition. Those who advocate changing it to recognize same-sex unions are not proposing a formal change in the law that will leave the institution unaltered even as it grants more people access to it. Rather, they seek a substantive change to the institution based on a new understanding of human sexuality. It is a mistake, and an important one, to believe that current marriage law is comparable to anti-miscegenation laws, and to advocate for the legal recognition of same-sex unions as marriages on the grounds that to do otherwise would be discriminatory. Instead, advocates should argue that same-sex unions as they do in fact exist in our society should be recognized because they are substantively worth recognizing. If our society decides not to recognize same-sex unions as a kind of marriage, however, it will not be guilty, at least with respect to its marriage laws, of discrimination.

David Schaengold is the assistant editor of Public Discourse.