Peter Kreeft

Do Squares Have Three Sides Because We Say So?

An Argument about Same-Sex Marriage from Dr. Peter Kreeft, May 2012

Moral Theology and Homosexuality
Audio Lecture

The current demand to redefine marriage to include same-sex as well as opposite-sex couples is often motivated by goodwill, the will to fairness and happiness, while opposition to this redefinition is often motivated by bad will, the fear or hatred of homosexuals. Nevertheless, the rightness or wrongness of same-sex marriage has to be decided on its own merits, not by taking the moral temperature of the advocates on both sides. For

  1. We have no reliable moral thermometer to stick into people's motives; and
  2. We often have bad motives for good deeds or good motives for bad deeds; and
  3. We need to judge the deed, not the doer.

Two Arguments From Authority

First, the Catholic Church has always taught, and always will teach, these two things with equal insistence: that we should love all sinners, both heterosexual and homosexual, and hate all sins, both heterosexual and homosexual; that we should love all persons, including homosexual persons, and that homosexual sex is "unnatural," "disordered,” and "sinful."

Many societies in the past did not believe the first of these two teachings ("love the  sinner"), but not one society in all of human history ever disbelieved the second, except for small  segments in ancient Greece and Rome. In the rest of the world this is still true, but in our society, i.e. in what we still call "Western civilization," it is exactly the opposite.

But the Church's counter cultural mission in every time and in every society is to try to conform the mind of man to the mind of God, not vice versa. This assumes, of course, that the Church has "the mind of God," i.e. divine revelation, and not just human opinion.

That is the essential reason for being a Catholic. And that is the decisive reason for Catholics to oppose same-sex marriage, even if they understand nothing else about the issue. If the Church is officially wrong about that, then she is wrong about her own authority as the infallible voice of God Incarnate; and in that case she is a false prophet, arrogantly claiming "Thus says the Lord" for her own fallible opinions.

And in that case she may very well be wrong also about anything else she teaches, e.g. that we ought to love all people, including homosexuals.

Second, a reason for opposing same-sex marriage is less decisive but still serious. It is not religious or definitive, only pragmatic and probable: it is what G. K. Chesterton calls "the democracy of the dead," the consensus of all other societies before our own. The vast majority of all mankind, a cross section of all times, places, cultures, and religions, is a serious authority. It is not infallible, and it may be wrong about some things, but that is far less likely than that only one culture, the one we happen to be in, is right and the rest of humanity is wrong. (And even in our culture, only a few nations, and none south of a certain line of latitude, have a majority of approvers.)

I can think of one and only one moral issue on which the vast majority of human beings in all societies in the past were wrong, and only religious Jews and Christians were right: that we should love everyone altruistically, absolutely, and unconditionally, even the wicked and even our enemies.

Argument From Reason

When we turn to arguments from reason rather than arguments from authority, the first thing we must agree about is the need to think honestly, open-mindedly, and clearly, especially about important things, and most especially about important things that we feel very passionate about, like sex. This is what I want to explore for a few minutes, as a philosopher.

It is true that we can change our thoughts, and change our definitions of things, of anything at all. Some of these redefinition's are possible—e.g. we can criminalize or decriminalize many things, including homosexual acts But some redefinition's are impossible. We can call squares triangles, but that does not make them into triangles. Calling call cats dogs does not make them dogs. And calling homosexual friendships marriages does not make them marriages. This does not depend on whether they are good or bad; it depends on what they are; it depends on their nature, their essence. 

Unless there are no natures or essences, i.e. unless we are complete nominalists, and therefore skeptics. (If you are one of these people, and if you actually practice the philosophy you preach, then please do not invite me to your house for dinner, for you must believe that it is impossible to draw a real and absolute line between people and animals, in which case you may be either a vegetarian or a cannibal—two tastes I do not share.)

What Is Marriage?

The whole question of homosexual marriage depends on just one thing: on what marriage is, or rather on whether marriage has a "what" at all, a nature. If marriage is not a natural essence but an artificial human invention, like a game or a human law, than we can redefine it because we invented it in the first place. Because we invented football, we can not only change the rules but we could even call it baseball if we wanted to. We could say there were two kinds of football, and one of them used to be called baseball. If we invent a thing, we can redefine it. If not, not.

The question can be phrased this way: is the answer to the question "What is marriage?” dependent on our reason or our will? Artificial things are dependent on our will, for we willed them into existence. Natural things are dependent on our reason; we discover them rather than inventing them. The decisive question about homosexual marriage is just that: whether marriage is artificial, man-made, and dependent on human wills, or natural, discovered, and dependent on human nature.

The issue is not just psychological, or scientific, or religious, or ethical, but philosophical, in fact metaphysical. The deepest reason why popular opinion has changed in favor of same-sex marriage in industrialized countries (but nowhere else) is that these countries no longer think in terms of what is "natural." We no longer understand, or feel the force of, the old notion of "nature," which meant the essence of a thing as manifested by its natural activities. The old notion of "human nature” assumed an inherent, unchangeable telos or purpose or design in it. E.g. "the reproductive system" was designed for reproduction, as the eye was designed to see. (Duh!) But to the typically modern mind "nature" means simply simply stuff, the universe, whatever we can see. It has become an empirical concept, not a philosophical concept.

That is why the notion of "unnatural acts" no longer has a holding-place in our minds. To the modern mind, the difference between homosexual acts (or desires) and heterosexual acts (or desires) is like the difference between the acts on what we now call a football field and the acts on what we now call a baseball field. "Different strokes for different folks" is quite reasonable there. And if football players have traditionally had special privileges which were denied to baseball players, we feel, quite reasonably, that this injustice must be undone. Let us be inclusive; let's include "baseball" under "football." Let's recognize the artificial quotation marks around these two terms. Let's be Nominalists: they're just man-made names, after all, not inherent natures.

An Illustration From Geometry

But suppose marriage is not like a game but like a geometrical figure, or a cat: something discovered, not invented. Then redefining it would be confusion. It would mess up the whole geometry of marriage, so to speak, as calling cats dogs would mess up the whole veterinary treatment of both animals.

And if marriage is as natural as geometry, then those who voted for a "Defense of Squares" act would not necessarily be motivated by a personal fear or hate of triangles, but by a love of geometry.

This is the first necessary thing for people on both sides of this deep divide to understand: that their opponents are not loveless cads, idiots or liars. There is an inherent reasonableness to both sides.

But they contradict each other. And therefore one side must be wrong and the other right. For the law of non-contradiction, at least, is not invented but discovered. There is no alternative to it. Its opposite is literally unthinkable. Contradictories are incompatible. The concept of "same sex marriage" may or may not be an oxymoron, but the concept of ”compatible contradictories" certainly is. Two propositions that contradict each other cannot both be true. That's why neither side can compromise: not because these two groups of people intolerantly exclude each other but because their ideas do. 

The traditional definition of marriage contains four properties, as a square contains four sides. If you subtract any one side from a square, you don't change the nature of squares so as to have a larger set of squares, one that includes three-sided squares as well as four-sided squares; you simply don't have a square any more, but something else, a triangle.

Four Dimensions of Marraige

That something else may be good or bad—it may be just as good as a square, or it may be less good—but it's not a square. It's a triangle. The four dimensions of marriage, as traditionally defined, are:

  1. Freedom
  2. Exclusivity
  3. Permanence, and
  4. Sex

It's the fourth dimension that is most in question today—though the others are also, and there is no reason why any or all of them cannot be questioned and changed if marriage is artificial, like football.

1. Freedom

Small children cannot marry because they have not yet the maturity to make such a binding covenant freely, just as they cannot yet make legal contracts. "Shotgun marriages” are not marriages then, for the same reason. They are oxymorons. Arranged marriages are not necessarily oxymorons, but they are valid (i.e. real marriages) but only if both parties freely consent to them.

2. Exclusivity

Marriage is between two persons, not one, not three, not many. There can be covenant relationships among more than two persons, but they are not marriages. They are friendships or communes or kibbutzes or states.

3. Permanence

Marriage is for life. Perhaps divorce is literally impossible (as the Catholic Church says), perhaps it is possible and permissible as an extreme, emergency treatment, like amputation, but it is not natural, normal, or intended. Marrying a person is not like leasing a car. That's why the argument for premarital sex and cohabitation ("let's give the car a road test before we buy it") is not only a bad analogy but an insulting one.

4. Sex

Marriage, as traditionally defined, obviously has something to do with sex. The sex between the married couple is to be (a) faithful and exclusive and (b) open to children (that's part of the definition of a family). This second feature is why it has to be heterosexual: because heterosexual sex, unlike homosexual sex, can and often does produce children. That's its nature, and its natural end, purpose, design, telos. (The "reproductive system,” remember!) And that's the aspect that's controversial today. Essential to the traditional idea of marriage is the idea that marriage, by its nature, produces children, is for children, is about children, is for the sake of children's existence and welfare.

That's the ultimate point of traditional marriage. To be complete, marriage needs children, and to be complete children need to be born into a marriage and a family. Every child needs the protection of a family, and every child needs two parents, not only to be procreated but also to be educated, by two different role models. Men and women are "hard-wired" with different instincts and different talents, and children need both. Deliberately depriving a child of a father or a mother is child abuse. What motivates (or should motivate) opposition to same~sex marriage is not hatred of homosexuals but love of children.

Notice how dependent this argument is on the old notion of "nature" and what is "natural." This is an a priori concept, not an empirical one. It's true that empirical psychological studies have reinforced it. But they cannot prove it. Such studies have shown that many psychological disorders come from the lack of a father or a mother in a child's life. But these studies cannot of themselves decide the issue, since they can only compare the probable consequences of the two different arrangements, not adjudicate their intrinsic rightness.

There's no way around it: philosophy is going to have to decide this issue. Or mythology, which is unconscious, instinctive philosophy. Is there such a thing as "the nature of things"? "To be or not to be, that is the question” not only for traditional marriage but also for Mother Nature herself. How big is the camel whose nose is newly under our tent? Read Brave New World, the most prophetic book of our time, to find out.


  1. US Conference of Catholic Bishops Resources
  2. Growing Up With Two Moms: The Untold Children’s View
  3. The Gay Divocees – (doubling to tripling the heterosexual rates)
  4. Effects on Children (largest parental study)
  5. The Faulty Argument: “It won’t affect current marriage)
  6. Study: Business-Friently States have Marriage Protection Ammendments 
  7. The Negative Effect on Massachusetts
  8. Myths and Facts
  9. Law and Seme-Sex Marriage
  10. Heritage Foundation "What is Marriage?"

Alternative MP3 Audio

From the Arlington Diocese (Washington D.C.) podcast:

  1. Deacon Levy—Christianity and HomosexualityAudio icon  (MP3, 79:07, 37MB)
  2. Fr. Scalia—Theology on Tap (Homosexuality)Audio icon  (MP3, 57:18, 27MB)