The recent US Supreme court ruling that legalized same-sex marriage unleashed an international wave of support for same-sex marriage, with millions of facebook users using the pride filter on their profile pictures. To many people on both sides of this issue, the debate over same-sex marriage is over, and is now merely a question of time. However, this cannot be an excuse for a stunted intellectual landscape. The best arguments from both sides have to be studied, both as a matter of historic record, and to be sure we don’t allow trite aphorisms cloud the real intricacies involved.
In this spirit, I consider two important arguments against same-sex marriage: in part I, I talk about the case from New Natural Law, while in part II, I consider a case by philosopher Amy Fry. Although I point out deficiencies of both arguments in Part III, I conclude by pointing out that the case for same-sex marriage gains valuable insights from the opposition. Although I consider only the questions of moral philosophy, and not the constitutional questions, I will draw from the Obergefell decision/dissents to showcase how the moral arguments play out  .
Part I: Natural Law and the case against same-sex marriage
Consider a scenario in which the government gives out driving licenses which are required to be able to drive a vehicle. Unfortunately, a person A has a rare genetic condition because of which they have terrible eyesight. Unsurprisingly, they cannot pass the driving test and hence fail to acquire a license. Is A being discriminated against because of their disability?
The answer seems to be an easy “no.” But surely, everyone has the right to travel and to move from place to place. Does the license requirement violate A’s right to travel? To answer this, we need to make a distinction between discrimination (such as in the case of A) and unjust discrimination. To determine whether a case of discrimination is unjust, we need to inquire into the purpose of the license. Since the purpose of licensing is to verify a person’s ability to drive, it would not be unjust to deny someone with bad eyesight a licence.
The New Natural Lawyers (NNLs) argue that in a similar manner, we need to probe the purpose of marriage to identify whether same-sex marriage bans constitute unjust discrimination. Note that what is salient for this question is the state’s purpose for being involved in marriage, not an individual’s reasons for getting married.
According to the NNLs, we need to try to spell out a principle (or a set of principles) which can serve as a plausible candidate for the state’s “purpose of marriage.” Why do we need a principle? In its absence, there is no rationale for who is included and who isn’t, which implies that anyone who is excluded from marriage is being excluded in an arbitrary manner.
NNLs then claim that there are two conceptions of marriage- a “conjugal view” that puts at its core the reproductive capabilities of heterosexual unions, and a “revisionist view” that puts at its core the emotional bond between individuals (importantly, neither conception is supposed to be inherently prejudicial). They spell these out as follows:
Conjugal View: Marriage is the union of a man and a woman who make a permanent and exclusive commitment to each other of the type that is naturally (inherently) fulfilled by bearing and rearing children together. The spouses seal (consummate) and renew their union by conjugal acts—acts that constitute the behavioral part of the process of reproduction, thus uniting them as a reproductive unit. Marriage is valuable in itself, but its inherent orientation to the bearing and rearing of children contributes to its distinctive structure, including norms of monogamy and fidelity. This link to the welfare of children also helps explain why marriage is important to the common good and why the state should recognize and regulate it.
Revisionist View: Marriage is the union of two people (whether of the same sex or of opposite sexes) who commit to romantically loving and caring for each other and to sharing the burdens and benefits of domestic life. It is essentially a union of hearts and minds, enhanced by whatever forms of sexual intimacy both partners find agreeable. The state should recognize and regulate marriage because it has an interest in stable romantic partnerships and in the concrete needs of spouses and any children they may choose to rear. 
One crucial feature of marriage in this argument is that it is supposed to have an essence independent of legal recognition. This means that a certain person’s conception of marriage can be true or false, depending on whether their conception corresponds to real marriage. What’s more, this essence consists in a married man and woman literally becoming one organism during intercourse, because they aim together at a common good: reproduction. All other forms of sex, even between a married couple, is really just mutual masturbation since their aim is solely self-pleasure (shockingly, this view isn’t very popular both inside academia and out).
The NNLs argue that their conjugal view explains away two problems that the revisionist view faces:
Problem 1: In their desire to make marriage more inclusive, the revisionists are forced to be too liberal with what is considered legitimate marriage, i.e., they no longer have a way to exclude polyamorous relationships (both multiple dyadic, and non-dyadic) from being recognized as legitimate marriage.
Problem 2: Revisionists do not have an explanation for why the state is interested in privileging sexual relationships at all. Consider two best friends who have decided to live together and take care of each other for life. Why does the state legally recognize and give benefits to them if they have a sexual relationship, but refuse to recognize their relationship otherwise? Even if we admit to sex being valuable to relationships in general, it doesn’t seem obvious that it provided any benefit or good to a couple that cannot be obtained in other ways. Hence the revisionist approach seems to render unintelligible the reasons behind state action, specifically those concerning the privileging of sexual relationships over non-sexual ones.
Before I talk about some serious objections to this view, it’s important to point out two commonly levied objections that don’t work.
One objection is that there are multiple reasons people choose to get married, and so singling out reproduction doesn’t seem to do justice to these. However this objection confuses the purpose of individuals who choose to get married with the purpose of the state in offering marriage as an institution. While these might overlap, they are distinct. To illustrate this, consider a government policy of offering deductibles for charitable donations to encourage charitable giving. Even if individuals use this policy with the sole purpose of paying lower taxes, the purpose of the policy remains distinct and unchanged.
Another common objection is that the purpose of state recognized marriage cannot really be tied intimately with reproduction because there is no official requirement of fertility, or of the presence of children for a marriage to be considered legitimate. However this confuses ends and means. Why would the government’s end of promoting reproduction necessitate a direct requirement of the presence children? The state can choose whatever reasonable means it deems fit to ensure that it’s end is met (within certain bounds, perhaps).
However, there are many serious objections that we should pay attention to. Here, I point out one major objections that has been raised.
According to the NNLs, marriage involves the man and woman in a union literally becoming one during intercourse, by virtue of them working in tandem towards the common goal of reproduction. The literal union is important as it offers a strong distinction between heterosexual intercourse and non-heterosexual intercourse. However, as philosopher Andrew Koppelman points out:
In reproduction, two entities share in a bodily action. That does not mean that they become one, even though the action they perform could not be performed by either of them individually. Two pianists playing a four hands piece do not become biologically one, even though they are using parts of their bodies in a complementary way. A chorus does not become biologically one even though its members are uniting their bodies to bring about a physical effect that no single human body could produce. 
Related to this problem is that status of sterile heterosexual couples. The NNLs seem averse to deeming the presently legal marriages of these couples as false or illegitimate, but as Koppelman shows, there doesn’t seem to be any way of arguing for this that doesn’t arbitrarily exclude non-heterosexual relationships
What sense does it make to postulate one type of sexual activity as normative in this way, so that heterosexual intercourse is held to be an act of reproductive kind even if reproduction is not intended and is known to be impossible? Why is it not equally plausible to say that all acts of seminal ejaculation are reproductive in kind, or to say that no acts of seminal ejaculation are reproductive in kind, and that reproduction is only an accidental consequence that may ensue under certain conditions? There is nothing in nature that dictates that the lines have to be drawn in any of these ways. 
Once we have discarded the idea of literal unification (as some of the natural lawyers seem to have done eventually ) we can recognize that non-heterosexual sexual activity can be a means to common goods as well, which could not have been achieved by either individual alone:
What common good might be realized in nonmarital acts?…pleasure, communication, emotional growth, long-term fulfillment…For sexual conduct can realize a shared experience of intimacy, one that is unachievable alone. Its goodness rests not (or not merely) in subjective states but also in mutual acts of genuine affection. Such interpersonal intimacy is sought, and achieved, even by partners who intend not to procreate. 
Hence, the NNL argument doesn’t seem to accomplish quite what it sets out to do. I return to this argument in section III.
Part II: “But no one is getting harmed! Why not?”
Amidst all this theorizing about principles and abstract ideas, one could be forgiven for wondering whether all of this is really required. Surely legalizing same-sex marriage will be incredibly beneficial to same-sex couples and their families, while it harms nobody. Why can’t we just accept same-sex marriage?
The response to this has two parts. The first goes back to the idea that in the absence of solid principles that serve as the purpose of marriage, any inclusion or exclusion is arbitrary. So, under this approach, we cannot simply accept same-sex marriage while arbitrarily excluding polyamory (for instance).
The second reason is that it is unclear whether is really is true if there are no negative effects at all. There are two relevant ideas to think about here.
1) A Burkean respect for “the wisdom of the ages,” where we respect institutions which have been handed down to us. After all, there may be many hidden reasons/advantages to a certain set-up that may not be apparent to us, but to which the survival of the particular institution may be a testament to.
2) Another issue is that society is incredibly complex, and so we might not be able to foresee what effects even a small alterations can cause, even if it is a worthy change. While it seems reasonable that legalizing same-sex marriage will have no immediate effects on present heterosexual marriages (except perhaps this one), the effect on “public mythos”  and the way in which future generations will think of marriage is more uncertain. As Philosopher Amy Wax puts it:
Traditionalists [assume] that conventions and individual conduct are effectively intertwined…The notion that fundamental revisions in modes of living, by altering social expectations, norms, and roles, will affect behavior in the long run is regarded as obviously true or at least plausible enough to counsel caution. In answer to the objection that barring homosexuals from marriage seems to have little to do with whether heterosexuals enter that state, traditionalists would point to how conduct is mediated by social meanings and understandings. The fear is that, if the institution of marriage is reshaped to give priority to diversity, choice, and individual prerogatives-and if marital roles are redefined to fit different homosexual and heterosexual lifestyles-then behavior surrounding all marital relations may change in response. 
As for why these sort of fears about change cannot be proven, Wax says:
By definition, traditionalist projections on the consequences of equality for same-sex relationships cannot be backed by data, since the proposed changes have not yet occurred-at least not on the large scale that proponents advocate…Those who resist change will rarely be able to answer the call for hard evidence of the detrimental effects that elicit their apprehensions. 
I return to these kind of considerations in the next section.
Section III: A case for same-sex marriage
In this section, I would like to discuss three ideas from the previous sections, and show how a better case for same-sex marriage can be built by taking them seriously.
1. It should be noted that Wax’s approach applies to all social change. So hers isn’t a particular defense of denying same-sex marriage, as much as calling for a blanket cautious approach to change. Moreover, we should remember that this caution could have been suggested on the cusp of any change- including the liberation of women, the ending of segregation, etc- and so should be carefully weighed against the demands of justice.
2. Consider the Natural Lawyers’ claim that equality can only tell us if unjust discrimination is occurring if we specify which conception of marriage is being used, but cannot tell us which conception of marriage we should prefer. As Law Professor Kenji Yoshino points out, this approach could be used to justify any form of discrimination . Imagine if someone claimed they had two conceptions of marriage, one that allowed inter-racial unions, and another that didn’t. They then claim that since equality isn’t violated under the first conception, and because neither conception is inherently prejudicial, we shouldn’t consider inter-racial bans unjust. Clearly this sort of argument would not be permissible- we want the principle of equality to be robust enough to evaluate the choice of conception also.
However, this raises the tricky question of what sort of considerations are relevant to judging whether a certain conception of marriage fails the principle of equality. Opponents of same-sex marriage insist that we need to take seriously the historic origins of the conceptions. This, it is claimed, is a significant difference between same-sex marriage bans and inter-racial marriage bans, since the latter originated with the sole purpose of demeaning certain races, while the former did not arise with any analogous malice. This is spelled out by Justice Clarence Thomas in a footnote in his dissent:
The suggestion…that antimiscegenation laws are akin to laws defining marriage as between one man and one woman is both offensive and inaccurate. “America’s earliest laws against interracial sex and marriage were spawned by slavery”…For instance, Maryland’s 1664 law prohibiting marriages between “ ‘freeborne English women’ ” and “ ‘Negro Sla[v]es’ ” was passed as part of the very act that authorized lifelong slavery in the colony…Virginia’s antimiscegenation laws likewise were passed in a 1691 resolution entitled “An act for suppressing outlying Slaves”…“It was not until the Civil War threw the future of slavery into doubt that lawyers, legislators, and judges began to develop the elaborate justifications that signified the emergence of miscegenation law and made restrictions on interracial marriage the foundation of post-Civil War white supremacy” …Laws defining marriage as between one man and one woman do not share this sordid history. The traditional definition of marriage has prevailed in every society that has recognized marriage throughout history…It arose not out of a desire to shore up an invidious institution like slavery, but out of a desire “to increase the likelihood that children will be born and raised in stable and enduring family units by both the mothers and the fathers who brought them into this world.” 
However, it isn’t clear if this is really convincing for three reasons:
- Even if marriage as a solely heterosexual union arose without animus towards gay people, maintaining this same conception after learning about same-sex relationships might involve animus. New evidence should surely be taken seriously when considering whether to stick with an older conception or alter it.
- In this particular debate, it’s unclear if procreative ends must necessitate the exclusion of same-sex relationships. Once the NNL idea of literal unions is rejected, we can separate a necessary link between reproduction and intercourse. It might have made sense in earlier ages to privilege heterosexual intercourse because it was the only means of numerically extending a family. However, considering the contemporary world contains means like adoption, surrogacy, sperm-donors, etc., it is unclear why same-sex couples should be excluded. As Kenji Yoshino points out, “same-sex couples are not sterile” . Hence, it is unclear if the state’s interest in reproduction is undercut by same-sex marriages.(One issue that can be raised here is that adoption, surrogacy, sperm-donors, etc., can be means of family extension for non-sexual relationships too. So would problem #2 from section I, namely that it is unclear why sexual relationships are being privileged, surface again? I try to answer this at the end of this section)
- One last issue with Justice Thomas’ answer is that even if we accept that the origins of the conception as salient to whether or not the conception violates the principle of equality, why should it be the only criterion? Another plausible candidate for gauging might be the actual effects of enacting the different conceptions into law. In this regard, Justice Kennedy’s chief point about how same-sex families, including their children, are actively being denied economic benefits as well as a sense of dignity is key.
3. An important assumption in Part I was that marriage had a pre-political essence. In many progressive cases as well, people attempt to find features which they deem as essential to marriage (Justice Kennedy’s “four principles and traditions” as well as Justice Robert’s “core structure of marriage” also come to mind, even though these were in the context of constitutional rights, not moral rights). However there also exists an alternate approach:
There is, however, another alternative view, which holds that marriage has no essence at all. It is a socially constructed practice, like chess, with goods that are internal to it. That practice can be changed when this conduces to human well-being…To the extent that the practice produces goods, there is reason to continue doing things as we have done them. 
Under this approach, marriage as recognized by the state is arbitrary in the sense that it doesn’t correspond with some pre-political entity, but is not arbitrary in the sense of being unjustified. (Some commentators wonder if considerations of justice can be applied to a construct at all , while others like Justice Thomas  seem to think that a principle of equality can lay no claims on government benefits. However, neither would probably contest that a newly constructed institution that benefited only one arbitrary religious group would fail the principle of equality, despite being a construct and involving only government benefits)
Once we incorporate Wax’s considerations as a decision heuristic (to exercise caution, ceteris paribus), we can answer a lot of the earlier challenges:
The reason the state is privileging sexual unions is explained by historic reasons, coupled with the Wax approach. We don’t know how society will look if any kind of relationships can be privileged in the same way as sexual ones. Right now, sexual relationships (whether dyadic heterosexual, or dyadic non-heterosexual) tend to be those kinds of relationships that we know tend to acquire children and build stable, prosperous families , so it makes sense for the state to privilege them to further promote the goods involved with marriage.
As for polyamory, there isn’t anything intrinsic about polyamory that makes it unsuitable for being considered marriage. However, applying the Wax rule again, we need to consider whether this is something we would like to recognize. An argument that has been made against polyamory has been that polyamory has typically, in the past, manifested as the incredibly sexist polygyny, where a single wealthy man marries multiple women. This means that there is a dearth of women for men of poorer economic stations, which deprives them of the opportunity to marry at all. In addition, there is an absence of evidence about how children do in polyamorous families, and hence we should take a cautious attitude. These sorts of considerations do not apply to same-sex relationships, considering we have decades of data about same-sex relationships not negatively affecting societal stability, or the well-being of children. Hence, at least for now, we have good reasons for legalizing same-sex marriage, while waiting it out in the case of polyamorous unions .
Before ending, I want to point out two features of the entire debate that are crucial.
First, I want to emphasize that this post wasn’t just about arguing for a certain position, as much as being about recognizing the rich web of ideas we need to navigate through to seriously engage in a debate as complex as marriage. There are a multiplicity of stances a person could take from just those mentioned above (ignoring the unmentioned). Someone could hold that a liberal state shouldn’t privilege any relationship type over any other because that would be making a value-judgement. One could hold that we should expand marriage to non-sexual relationships, while others might hold that it must be expanded to at least some versions of polyamorous relationships. Still others might still think that the position of the New Natural Lawyers is the most coherent, and that I’ve given them short shrift. Whatever the case, I hope that there are now new tools with which issues can be studied and argued.
Second, I hoped to have stressed how incredibly complex this debate actually is. Too often political debates shrivel into deaf exchanges of buzzwords and insults, instead any kind of substantive exchange. Hopefully, this post will have impressed upon readers how complex this issue can actually be (of course, this is not to say that individuals on either side actually are in possession of sophisticated reasons for their current beliefs), and so it is important to shy away from resorting to branding opponents with charges of bigotry and malice lightly. I end with a quote from a petition signed by many of the very people I have cited in this post:
The natural consequence of true liberty is diversity. Unless a society can figure out a way to reach perfect agreement, conflicting views will be inevitable. Any effort to impose conformity, through government or any other means, by punishing the misguided for believing incorrectly will impoverish society intellectually and oppress it politically. The test of our commitment to liberal principles is not our eagerness to hear ideas we share, but our willingness to consider seriously those we oppose.