Those who argue against the legalization of same-sex marriages insist that marriage is ordered toward the procreation of children and that the legal supports given to marriage are given with that end in view. Marriage needs the protection of laws because society must be concerned about its own preservation and continuity into the next generation.

Those who argue for legalization claim that the abiding friendship between the two persons should be acknowledged by law, and the legal benefits accruing to marriage should be made available to the partners. As a letter in The Wall Street Journal stated, “Marriage is a personal decision of commitment and love, and should be as open to homosexuals as it is to heterosexuals” (3/27/96). The essential point in the argument for legalization is that marriage as an institution sanctions a friendship, not specifically a procreative relationship.

Defenders of same-sex marriages often ask their opponents what they fear. What damage will follow from legally recognizing same-sex unions? How will such recognition threaten heterosexual marriages? I would like to address this issue by identifying some of the consequences of giving same-sex marriages full legal status.

I.

Suppose the laws were to recognize homosexual marriages. Then suppose I were to come along and say: “My uncle and I [or my aunt and I, or my sister and I, or my mother and I, or my father and I, or my friend and I] live together. We are devoted to each other, but we don’t engage in mutual sexual conduct. We want to get married in order to get the legal benefits of marriage that affect property rights, taxes, insurance and the like.”

The reply would probably be negative, at least at first. The laws would say, “You cannot get married.” Why not? “Because you don’t exchange sex.” That is, the homosexual marriage will become the paradigm. The exchange of sex, and specifically nonprocreative sex, will be what defines marriage. This new definition of marriage would be implied by the refusal to let my uncle and me get married, not because we cannot have children but because we do not choose to have sex. A procreative marriage would then only accidentally be a marriage. Procreation would no longer specify what a marriage is.

Once this new definition of marriage is in place, subsequent laws would have to shore it up. What effect would this development have on the public sense of family and marriage? What effect would it have on sex education? It should also be noted that this understanding of marriage would bring the government into the bedroom with a vengeance, because it would be necessary for it to verify that those who are married are indeed having sex.

The new reproductive technologies make procreation possible outside of sex, and this reinforces even more the accidentality of procreation to marriage. A partner will be able to make a withdrawal from the sperm bank and have a child, but that partner will be married to no one related to the birth of the child: neither to the sperm donor, nor to the sperm bank, nor to the inseminating health care provider.

But suppose the reply of the laws to my demand to marry my uncle or aunt is: “All right, we will declare you married. We have already separated marriage from reproduction, and from now on we will separate marriage from sex entirely. Any two people who live together can get married.” After all, if homosexual couples are discriminated against because they cannot get married, why should any two people who live together, even those already related by prior “familial” bonds, such as uncles and nephews, be discriminated against? Any persons who form a household should have the right to be married.

What effect would this have on the sense of marriage? I could marry my father (even Oedipus was never in danger of doing this, so far have we surpassed the wisdom of the ancients). I could marry someone I plan to live with for a few years, just for the benefit of it all. Suppose I were to move in with my grandfather who is seriously ill, to help him out in his last days. We could get married for the legal benefits and to facilitate the inheritance.

And once this has been done, why not permit polygamy and polyandry? Why discriminate against groups, if just living together is the only requirement for marriage? I could marry not just my mother or father, but both of them together, in a truly deconstructionist gesture, thus joining not with one but with both of the sources of my being.

If this were to occur, there would be very little left of such other familial relationships as those of grandparents, uncles and aunts, cousins and the like. Such relationships have already been attenuated by the prevalence of divorce, remarriage and single parenting: the “network” of relatives is deeply modified when some children in a family have different grandparents and cousins than their siblings do. In cases of artificial insemination by an unknown donor, the child is not related even to his or her biological father and his family. Such a dilution of extended familial relationships is a loss of a great human good; it damages an important dimension of personal identity. People become anonymous individuals, left to define themselves instead of being given a role and place in life.

We could even go one step further and ask why people should have to live together to be married. If there are legal and financial benefits to the union, why should they not be available to any people who wish to take advantage of them? The choice to be benefited should override the accidentality of living together, so long as there is a modicum of commitment and friendship among those people.

If “marriage is a personal decision of commitment and love,” why should it not be open to whoever is (or says he or she is) committed to and loves anyone else to a greater or lesser degree, whether singly or in a collective? And why must that love be erotic? The major threat that same-sex marriages pose to traditional unions is that they redefine the institution of marriage.

II.

Marriage has traditionally been understood to be a human relationship ordered toward reproduction. The “end” of marriage is procreation. To understand this claim, it is important to distinguish between ends and purposes, a distinction introduced by Francis X. Slade.

Purposes are goals that human beings have in mind when they act; they are wished-for satisfactions, intentions, things that people hope to obtain through their choices. Purposes arise only where there are human beings who are capable of deliberation and action. Ends, however, are found apart from the intentions and thoughts of human beings. Ends belong to things; they are how things function when they are working according to their own natures, when they reach the perfection that is proper to them. The end of medicine is to preserve or restore health, the end of an axe is to cut. Ends are there apart from human willing. We cannot will even an artifact, like an axe, into being something that it is not.

When we use things, purposes and ends interact. A man may pursue many different purposes in practicing medicine. He may strive to become rich, gain a reputation or alleviate suffering, but in all these purposes the end of medicine remains what it is, the preservation or restoration of health. An agent may pursue different purposes in using an axe: he may clear a forest, prepare firewood or attack someone, but cutting remains the end of the axe. Human beings, as they pursue their purposes, may or may not respect the ends inscribed in things. If they fail to respect these ends, they will bring the thing in question to ruin. If medicine is practiced in a way that does not preserve or restore health, it will die out as an art, and if an axe is used in a manner that contradicts cutting, it will rust, chip or fracture. As Slade has put it, there is an “ontological priority” of ends over purposes.

A very important element in our modern culture is the belief that there are no ends in things; there are only purposes. One of the names for this belief is “mastery of nature.” We think we can redefine all institutions, relationships and things, because whatever seems to be “natural” to them is really only the result of earlier choices that other agents have made. Their apparent “nature” is only a significance that we have projected onto them. We can introduce new purposes and redefine government, sexuality, birth and death, education, and marriage and the family. We can reinvent anything, because whatever there is has been invented, not discovered, by someone else. There are no ends in nature, so we can use everything according to our own purposes, to satisfy our wants, and nothing in our nature prescribes what we should want. We are free: “At long last our ships may venture out again; …the sea, our sea, lies open again; perhaps there has never yet been such an ‘open sea’” (Nietzsche, The Gay Science [1882], No. 343).

It is exhilarating to think that we can redefine everything, ourselves included, in this way. It is easy to address people with rhetoric about “liberating” themselves from the prejudices and restrictions of the past and to encourage them to exercise a kind of small-scale omnipotence. We are invited to choose our own values and define our own understanding of happiness. Furthermore, since people have become used to thinking that things in general do not have natures and ends, it is hard for them to think that sexuality and marriage have ends. Consequently, the proposal to redefine marriage seems appealing to many, especially our cultural elites.

III.

Sexuality has as its end the procreation of children, but the common use of contraception and the way sex is presented in our popular culture have totally separated sex from procreation in public opinion. Sex is understood as an end in itself. The reigning opinion is that a woman gets pregnant by accident, by not taking precautions, not because sexual activity is procreative and its natural outcome conception. This is a great reversal of nature and accident. Furthermore, it is said that every child must be a wanted child, which implies that the child is loved because the child has been chosen, not because he or she is there.

It is often said that we have recently arrived at a new and different sense of sexuality and marriage, but this claim is incorrect; both are what they always were. To say that mutual love is on a par with procreation as an end in marriage is misleading. It is obviously very important, but not as a simply parallel good. Rather, the end of procreation is what specifies this relationship; the physical end of procreation is the first and essential defining character of marriage, and sex is defined as the power to procreate. Then this relationship, so defined, is to be informed with friendship or love, that is, mutual benevolence; but the kind of love it calls for is qualified by the type of relationship it is.

Even in the Catholic Church after the Second Vatican Council, people have been quick to introduce mutual love as an end of marriage on a par with procreation. It is, of course, an end of marriage, but not the same kind of end as procreation is. It is not an alternative end, but one based on and specified by the procreative relationship.

People who separate sexuality from procreation, whether in their thinking or their actions, live in illusion. They lie about this matter, to themselves and to others. Furthermore, this error occurs not about some marginal human thing, but about the mystery of our own origins. It is an illusion concerning one of the most powerful human emotions and tendencies. Once we live in delusion about such an important issue, we will inevitably be misguided in regard to many other human things: religion, human relations, laws, governmental policies, moral judgments and even our cultural inheritance. The most obvious truths become obscured.

IV.

The state does not establish legal categories for many different forms of human friendship. Why does it do so for marriage? Because it has an interest in society’s next generation. The continuation of the population is a condition for the survival of the body politic. It is this focus on population and reproduction that justifies laws concerning marriage. Even marriages between people who cannot have children, such as older people, depend on procreative marriages for their sense and legal standing. Society has an interest in seeing that there will be a next generation and that it will be brought up to be virtuous, law-abiding and productive. By its actions, therefore, the state has traditionally recognized reproduction as the end of marriage.

Proponents of same-sex marriages want to unlink marriage from reproduction and have the laws legalize their friendship because it is a friendship, not because it is procreative. But once the state legalizes one kind of friendship, it cannot stop at that; it will have to legalize any and all friendships for which legalization is sought.

The concept of same-sex marriages leads to impossibilities, because it contains a contradiction. Its proponents do not recognize the contradiction, because they think that nothing has a natural end, and specifically they think that marriage and sexuality do not have natural ends. They think that choices and purposes are the only things that matter, and that the private choices they make, their “personal decisions of commitment and love,” must be ratified and supported by public law.

This article appears in June 7 2004.