Many who self-identify as “gay” are not shy about appealing to nature to justify their lifestyle. They often say, “I was born this way” or “It’s natural for me to feel attracted to members of the same sex.”
What they mean is that they didn’t consciously choose their attractions, so they must be natural. And since they’re natural, they must be good.
I believe most are sincere when they say they didn’t choose their desires. But when you think it through, it becomes evident that the conclusions they draw from this are flawed.
Here are three reasons why.
A wrong understanding of “the natural”
First, just because someone has a desire or inclination he didn’t choose, it doesn’t follow that the inclination is natural or that it’s morally permissible to indulge it.
Suppose, for example, a man discovers that he has an inclination to be sexually aroused by children, and he is in no way responsible for it. Would we say therefore that such a tendency is natural, thereby justifying him to engage in sexual behavior with children? What if he was sexually aroused by animals (zoophilia), or corpses (necrophilia), or thoughts of rape?
What if he felt an unchosen inclination to abuse alcohol (alcoholism), or to set fires (pyromania), or to eat dirt or other non-food substances (pica)?
If we follow the logic of the “It’s Natural for Me” argument, we would have to say that these inclinations and others are natural and that the behaviors associated with them are therefore good—because he was just born that way. But that’s absurd.
What’s nature got to do with it?
The argument is absurd because it confuses deep-seated subjective desires with nature’s purposes. A “natural inclination” is not simply anything a person happens to feel. It is the inherent directedness of a thing’s capacities toward goods that perfect it, according to its nature.
For example, given the nature of a fish, it must live under water. Therefore, the inclination to swim and breathe underwater is natural for the fish. To use another example (an example of the philosopher Edward Feser), it belongs to the nature of a tree squirrel to climb trees and collect nuts. Inclinations to these sorts of behaviors are therefore natural for the squirrel.
If there were a fish that felt inclined to jump out of the water and flap on the banks of a river, it would be an unnatural inclination. If a squirrel felt moved from within to lie flat on the road and eat toothpaste, it would be an unnatural tendency.
A similar line of reasoning can be applied to human beings. We all have a common nature with capacities directed to goods that will perfect it (and the frustration of which will harm it; see Summa Theologiae I-II:94:2). To the degree that a behavior perfects our nature, it is natural. To the degree that it is destructive, it is unnatural.
For example, an inclination to undue violence destroys peace in society, to which we as humans are generally ordered given our nature as social animals (violence in just war works to reestablish peace). An inclination to alcoholism is unnatural because it enslaves a person to a substance that impairs his highest and noblest capacity: reason.
What’s sex got to do with it?
Reason tells us that our nature likewise directs our sexual faculties to certain ends: procreation and unitive love. Therefore, natural use of those faculties will be ordered to those ends. Using them in a way that frustrates those ends (e.g., contraception, sexual activity among members of the same sex, bestiality, masturbation, etc.) is unnatural, no matter what desires a person feels inside.
It follows that sexual inclinations are natural to the degree that they harmonize with nature’s ordination of our sexual powers. Since the sexual desire for members of the same sex does not harmonize with nature’s ordination, it is unnatural. This is what the Church means when it teaches that homosexual tendencies are “objectively disordered” (CCC 2358).
But, some would ask, doesn’t the existence of those tendencies in some people mean that nature’s ordination for our sexual faculties isn’t strictly or exclusively normative? Maybe they just have a different nature.
It’s true that for the most part our desires do match up with nature’s purposes. For example, we desire to eat and drink because nutrition is good for our nature. However, just like everything else in the natural order, sexual desires are subject to imperfections and distortions. Sometimes we can have deformed desires that turn us away from what nature intends. And regardless of whether these desires are the result of genetic defect, habitual vice, peer pressure, irrationality, or mental illness, they are still unnatural.
An inconsistent appeal to “the natural”
A third reason why the “It’s Natural for Me” argument is unreasonable comes from Providence College professor Paul Gondreau, who argues that those who make it are being inconsistent in their appeal to nature. Why is it okay, he asks, to dismiss nature as irrelevant at the common level of our species, which includes our biological design, but insist it’s relevant at the level of the individual, in the case of a person who feels that same-sex attraction is part of the “way he was made”?
Something in common
The claim that same-sex attraction is unnatural should not be taken as a condemnation of those who experience it. If that were the case, we would all be condemned, since we all experience unnatural tendencies in various forms. The root for such tendencies is called concupiscence (see CCC 1264), and it’s a result of the Fall.
If we think it through, the claim is a reminder that we should not let unnatural inclinations dictate our life choices. We are human, and therefore should work to excel in the art of being human—that is to say, to live in accord with what reason (and God) tells us is perfective of our human nature. Only then can we be truly happy.
 In his Nova et Vetera article “The Natural Law Ordering of Human Sexuality to (Heterosexual) Marriage: Towards a Thomistic Philosophy of the Body.”