Making the Case:

The Argument from Crucial Distinction

What is the difference between marriage and non-marriage?

The Argument from Crucial Distinction holds that if our view of marriage does not offer a meaningful, non-arbitrary distinction between marital and non-marital relationships, and if that distinction is not strongly connected to central marriage norms such as sexual activity, monogamy, fidelity, and permanence, then our view of marriage more than likely gets marriage wrong.

The Argument from Crucial Distinction further holds that the conjugal view of marriage offers just such a non-arbitrary distinction between marital and non-marital unions, while the revisionist view of marriage does not. The Argument from Crucial Distinction makes no moral judgment of same-sex relationships, except that they are philosophically distinct and different from the conjugal union of marriage.


The Argument from Crucial Distinction starts with something non-controversial, or at least something that shouldn’t be controversial: “Marriage” identifies a unique form of relationship that is distinct from other relationships, such as friendships, business or tennis partnerships, roommates, or even just sexual lovers. Otherwise, there would be no purpose in debating these matters at all. The real question is, how is marriage meaningfully different from other relationships?

A Non-arbitrary Difference

First of all, marriage must be distinct from other relationships in a meaningful way. Said in other words, there must be a non-arbitrary distinction between marriage and other kinds of relationships in our minds and in our laws if we are to fashion any sensible marriage policy. Otherwise, the concept of marriage has no meaning and serves no purpose.

Secondly, any such distinction should be related to the norms, or central expectations that marriage calls for, including sexual activity, monogamy (that is, two partners only), exclusiveness, fidelity (that is, loyalty), and permanence. For example, most people agree that married people should stay together unless there are very good, overriding reasons to separate. Most people presume that married partners are (or at least have been) sexually active. Most people presume that marriage relationships are exclusive in regards to those sexual activities. Why? Any good view of marriage must identify what about marriage makes sense of these norms. If our view of marriage does not offer this, it likely gets marriage wrong.

Essentially, there are two competing views of marriage: the conjugal (or traditional) view, and the revisionist (or modern) view.

The Conjugal View

In the conjugal view, marriage involves two partners sharing a domestic life that is directed towards and naturally unfolds into procreation and child raising. That is, partners in a marriage unite — or coordinate — towards procreation. In this view, marriage is different from all other relationships because its unifying good is procreation. No other relationship, be it roommates, siblings, best friends, or boyfriend/girlfriend, share that unifying good.

This unifying good (that is, procreation) explains why marriage implies sexual activity: in order to bring children into the world. That would make sense of why we presume marriage partners are sexually active. In addition, this unifying good explains why monogamy is expected of married people: because two and only two people, one man and one woman, can biologically create children. This also explains the expectation of fidelity and permanence: because bringing children into the world requires life-long support and undivided commitment both towards each other as spouses and towards shared offspring. Marriage ought to include each of these norms because of its connection to new human life, and the lifelong duties that the potential for children brings to the marriage partners.

So the conjugal (or traditional) view of marriage offers a meaningful distinction that both distinguishes marriage from broader forms of companionship and makes sense of important marriage norms. Marriage is an institution that enwraps norms of permanence, fidelity, monogamy, etc. around the sexual act that has potential for procreation, and procreation calls for those norms.

The Revisionist View

On the other hand, in the revised and changed view of marriage, the view that makes room for same-sex marriage, marriage is thought to reflect a deep emotional connection between partners. From this view, romantic love is the crux of marriage — marriage is simply your “number one relationship.” Instead of procreation, the unifying good of marriage (from the revised view) is mutual personal fulfillment. However, many non-marital relationships — such as chess partners, dating relationships, or best friends — can also share a deep emotional connection, coordinate towards mutual fulfillment, and be a person’s “number one relationship.”

When marriage is viewed in this light, there is no particular reason marriage ought to be sexual — if the purpose of sex is to build the relationship and to seek personal fulfillment, why can’t it be interchangeable with non-sexual romance, other affectionate activities, or other relationship-building pursuits? There is also no reason for marriage ought to be monogamous — why can’t three or more individuals also share a deep, mutual fulfilling, emotional connection? There is no reason for fidelity or exclusivity to be obligatory — many couples claim that their emotional connections are strengthened as they seek sexual satisfaction with partners outside the marriage relationship. And lastly, there is no particular reason marriage ought to be permanent — emotional connections come and go, and a relationship that is fulfilling one year might not be the next.

From the revised view, marriage can be sexual, monogamous, exclusive, and permanent, but there is just no reason to say that marriage ought to be those things (since marriage is whatever the partners want it to be). In other words, there is no reason for these to be marriage norms (that is, expectations of married people), rather than matters of personal preference. And there is no basis in law to distinguish marriage from other relationships where those norms are not essential (such as friendships, housemates, etc.).

So we have no meaningful distinction, and any distinction that does exist from the revisionist view provides no good reason for important marriage norms. These norms should, from the revisionist view, just be matters of preference, rather than expectations.


In conclusion, the conjugal view gets marriage right in ways that the revisionist view gets marriage wrong. The conjugal view explains how marriage is different from other relationships in a non-arbitrary way, and makes sense of the norms that most people associate with marriage. The revisionist view does neither. This argument has nothing to do with sexual morality. We can celebrate lifelong homosexual relationships, and believe they are moral and good, and still accept this argument in favor of traditional marriage.

Questions and Answers

What about infertile or older couples? Are their relationships disqualified from marriage?

No, they are not. The conjugal view holds that procreation is the unifying good of a marriage relationship — it does not hold that marriage is only a human good insofar as couples successfully procreate. That is, marriage is union in which the partners coordinate towards the good of procreation; this does not mean that partners are not legitimately married if they do not succeed in the desired end. The idea of a practice having a unifying good that defines the practice, but which does not require success (or even the expectation of success) is not an aberration in human affairs — it is so common that it is virtually unnoticed. Consider some other examples:

  • People engaged in commerce are uniting towards the unifying good of making money or creating value in the world, but this does not mean that people are engaging in commerce only insofar as they successfully make a profit.
  • The unifying good of an election campaign is to get a candidate elected to public office. If you and your team advertise, solicit votes, participate in debates with other candidates, etc., but you don’t win the seat, you are still engaging in campaigning.
  • Throwing and catching balls in a field while running laps does not make a game of baseball — the team must at least be coordinated towards the good of winning the game, even if they are not successful in doing so.
  • The purpose of hunting is to kill and/or capture an animal. If you carry weapons into the wilderness, stalk prey, take shots at them, etc., but you never bag an animal, you are still engaging in hunting. (Try telling the game warden, when he fines you, “But I never actually hit anything, so I wasn’t hunting!”) But shooting arrows or bullets into a cardboard target on the range is not hunting (even though the activities may be similar).

But the real question is, why would we want to enwrap infertile relationships with the institution where permanence, fidelity, sexual activity, and monogamy are normative if those norms are instrinsically connected with procreation? The truth is that there are good reasons for including infertile couples in this institution, and treating those norms as obligatory for infertile married couples — first, infertility tests are often inconclusive, and couples once thought to be infertile have often concieved regardless. In addition, these stabilizing norms have historically and legally been connect to the marital act of coitus, but not to any other sexual act — not to exclude gays, but because of the act’s connection to conception. Infertile couples can participate in the marital act of coitus, and by so doing — even when they are infertile — create the change of new human life.

These are just a few of the reasons why someone can consistently believe that infertile or older couples should marry while same-sex couples should not. There are many, many more ways to explain why — so many that we created an entire article to address this question. Check out the Objection from Infertility.

Isn’t this essentially a “slippery slope” argument, and therefore a logical fallacy?

The Argument from Crucial Distinction is not a slippery slope argument. It is not arguing from the basis of historical inevitability, but on the basis of philosophical consistency. It is not saying that other unions will be formalized as well — it is simply saying that the revisionist view offers no compelling reason why they shouldn’t be. It is saying that the distinction between conjugal marriage and all other companionate relationships is non-arbitrary, while the distinction between companionate marriage and all other companionate relationships is arbitrary. Patrick Lee explains:

Suppose Joe, Jim, and Steve have a committed, stable, romantic-sexual relationship among themselves—a polyamorous relationship. On what ground can the state promote the relationship between couples, but not the relationship among Joe, Jim, and Steve? The argument here is not a slippery slope one. Rather, the point is: There must be some non-arbitrary features shared by relationships that the state promotes which make them apt for public promotion, and make it fair for the state not to promote in the same way other relationships lacking those features. Without this the distinction is invidious discrimination.

The conjugal understanding of marriage has a clear answer: (a) marriage is a distinct basic human good, that needs social support and that uniquely provides important social functions; (b) marriage’s organic bodily union and inherent orientation to procreation distinguish it from other relationships similar in superficial respects to it. But the same-sex marriage proposal’s conception of marriage has no answer. In fact, its conception of marriage is actually an arbitrarily selected class, and so the enactment of this proposal would be unjust.1

Many vocal supporters of same-sex marriage have already openly admitted that the revisionist view of marriage does not provide a compelling reason why we shouldn’t formalize polyamorous or even non-sexual unions. In short, there is no non-arbitrary reason why a marriage relationship should be confined to two people, or even to sexual partnerships. This is not a slippery slope claim, but a requirement of logical consistency.

Isn’t personal fulfillment an important part of marriage?

A good marriage can — and probably should — be personally fulfilling. There is nothing about the conjugal view that shuns or even downplays some of the most enjoyable aspects of a marriage relationship. We can value personal fulfillment in marriage, and even value it highly — the conjugal view simply states that it is not the highest good or the defining feature of the institution. Personal fulfillment can and most often does flow from marital relationships, but it is not the overriding good of marriage.

Think of it this way: if personal fulfillment were the unifying good of a marriage relationship, as soon as the relationship becomes less enjoyable (and other, more enjoyable prospects arise), there is no basis on which one can say that the couple ought to stay together. Thus, the norms of permanence and fidelity become less important. But if the unifying good of the marriage is procreation, the oughtness of permanence and fidelity makes much more sense.

Isn’t love an important part of marriage?

Yes, very much so. We think that married couples ought to love each other — in fact, love is just as much a marital norm as permanence, fidelity, monogamy, and sexual activity. The main reason we did not include love as a marriage norm the article and the video is to draw the contrast between the two views of marriage more starkly and clearly. Our societal understanding of marital love has changed, however. We’re not talking about infatuation, intense sexual attraction, or really most things under the umbrella of “romance.” We’re talking about the kind of love turns a home from a battleground to a haven of mutual respect, service, and consideration.

However, today, when we talk about the “marital love,” people often assume that we are talking about the romantic, sexually-charged infatuation that we see depicted in most Hollywood films. There are strong arguments that this kind of “love” is heavily influenced by hormones and other factors that are sometimes outside of our conscious control. From this view of marital love, when we say, “Married couples ought to love each other,” we are in fact implying that married couples who do not have these feelings as strongly as they wish ought to separate. That is, we end up implying that the longevity of marriage depends entirely on factors outside of our control — norms of permanence and fidelity become the slaves of passion. This kind of love is a great benefit to married partners, but it should not and cannot be the defining feature of marriage.

Now, of course, a marriage relationship that has neither form of love can be a dangerous place to raise children. A home without mutual respect, consideration, and service becomes a battleground of familial conflict. If one or both parties are unwilling to change and learn to love each other, this might very well be grounds for divorce, perhaps for the protection of children involved. But saying that couples “ought” to love each other, in this sense, implies less that they ought to divorce if that love doesn’t presently exist, and implies more that they ought to change (with divorce being a tragic last resort if a partner stubbornly refuses).

Is this argument circular reasoning? Aren’t we saying that these marriage norms are part of marriage, and then finding a view of marriage that makes sense of those norms?

No, it is not. We are grounding our argument in our moral intuitions about what the critical features and norms of marriage are, and then testing different theories of marriage against those norms. We believe that most people intuitively recognize that these norms are essential features marriage, or at the very least implied by our marriage customs. Ask people whether or not married partners should stick with their marriage, even when times get tough, and most will say yes.

Research strongly shows that permanence and fidelity in marriage are vital social goods that benefit children in substantial ways. This research will be the subject of a future article — the Argument from Crucial Distinction is ultimately a philosophical argument, not an empirical one, although its premises are empirically substantiated. But even philosophical arguments have data against which we can test a philosphical theory, such as our moral intuitions. And when tested, the conjugal view comes out on top.

References and Further Readings

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