Introit for the Third Sunday in Lent

Mine eyes are ever looking unto the Lord, for he shall pluck my feet out of the net: look thou upon me, and have mercy upon me, for I am desolate and in misery.
Unto thee, O Lord, do I lift up my soul: my God, in thee have I trusted; let me not be confounded.
Glory be to the Father, and to the Son, and to the Holy Ghost; as it was in the beginning, is now, and ever shall be, world without end. Amen.

Monday, June 2, 2014

A Question I Have No Good Answer To

Why is it wrong?

Since childhood, with only a relatively short period of wavering in my late teens and early twenties, I have taken the Bible's word for it -- and, since 2008, the Catholic Church's word for it -- that gay sex is wrong. I've never truly understood why; I don't have the revulsion from it that a lot of straight people do (though certainly a lot of straight people don't have that response either, my favorite reaction probably being that of C. S. Lewis, who for his part described homosexuality merely as "opaque to the imagination").

This is what I think of when I think of things being "opaque to the imagination."

I don't mean by this that I don't follow the syllogism of natural law generally used to defend the Church's position from a strictly philosophical, as opposed to a religious, standpoint. The argument of natural law is widely misunderstood, so I'll take a brief detour to explain it.

The argument from natural law isn't an argument that homosexuality doesn't occur in nature, which would be utterly ridiculous. I dare say some Christians have attempted to make that assertion (and there are probably a great many more who didn't mean that exactly, but who spoke with sufficient carelessness or stubbornness as to leave the impression that they did*), but this, even if it were true, wouldn't have anything to do with the natural law argument.

Rather, the idea of natural law to which Catholics appeal here is that of the law of human nature -- and by that meaning, not whatever human beings happen to be like, but that to which human beings are called by our specific character as rational animals. Our animality, obviously, includes plenty of things we share with the animal kingdom as a whole; what is under discussion here is that which is specifically human, specifically rational -- that which can fall under the categories of morality.

To take an extreme example, in this sense of natural law, it is unnatural for one man to kill another. This statement doesn't mean that men don't in fact kill one another on occasion; it means that it goes against that nature which is specifically human to do so. For one animal to kill another wouldn't necessarily be unnatural, because animals don't have rational souls and therefore don't have a moral compass or responsibility, so they wouldn't be contradicting their own natures to do so.

Admit it, you were waiting for him to up and kill some folk the whole series.

Now, the contention of natural law theorists** about homosexuality is not that it is arbitrarily wrong for us, though innocent among animals. It is that the reproductive system is, well, a system designed with the purpose of reproduction***, and that the proper activity of rational beings like ourselves is to use things in accordance with their purpose -- or, at the very least, not use them in a way that contradicts their purpose. Insofar as homosexual sex, by definition, can't lead to reproduction, it is therefore defined as wrong by the nature of the act.

If you're like me, you have one or both of two reactions to that line of argument:

1. That makes total sense.

2. But fuck that noise.

It's always been vaguely surprising to me that I can be both in full agreement with, and at the same time bitterly scornful of, the same argument. I've been grateful to have something more than "Because God says so" as a reason for having to regard being gay as a cross, instead of just a thing, with no moral implications. And when I look at this argument with detachment, trying to imagine as far as possible how I'd feel if I were evaluating it objectively and as someone who wasn't affected by its truth or falsehood, I have to assent that it's perfectly sound. Yet, as I've discussed with a few of my fellow queer believers, the consequences of living in accord with that belief -- the loneliness, the confusions and misunderstandings, and, yes, the blue balls -- seem grossly out of proportion to the gravity of violating it. I mean, seriously? It's so wrong to use something out of accord with its intended purpose that it's literally better for a gay guy or a lesbian to live alone for seventy years? It's like saying that it's better to have your hand chopped off than to use a wrench to pound a nail in!

Q: How many lesbians does it take to change a light bulb?
A: One, I assume. That's kind of a weird question; what brought that up?

Convincing though I find the natural law argument in principle, I personally would not be able to maintain my belief in it -- or at any rate, I wouldn't be able to care -- if the authority of the Church didn't back up the conclusion as the bearer of revelation. It so happens that the Church does, and I can. Nevertheless, at a heart level, I'm not satisfied, and for that reason (among others) I cannot bring myself to look sternly upon those who can't accept the Church's teaching on this subject.

I look forward with some small hope to the day when I'll understand, but for now, I have to acknowledge that I don't feel I have a good answer to this. Do I trust the Church? Of course. But having food that keeps you alive is not the same as having food that makes you feel full, or even being healthy.

I do, however, have an incomplete hunch. I've long suspected that the biological and reproductive angle was the wrong tack to take. The body, after all, is matter; and matter isn't bad, indeed, it's good, but matter doesn't get its significance from itself -- it gets it from the spiritual realm. God is spirit and God created matter, so this is true automatically, and it is specially true of what we might call spiritualized matter, i.e. the body and the seven sacraments.

Now, God, according to Catholic theology, is Trinity, and this means among other things that relationship is at the heart of all existence. This is part of what is meant by the famous phrase "God is love." The simultaneous unity and differentiation of the Divine Persons makes all of their relationships asymmetrical: God the Father begets God the Son and God the Spirit proceeds from both. No two relationships within the Trinity are exactly alike. Proper modes of relating are therefore not only important, they are of the essence of reality.

Depicted: blueprints for existence. Handle with care.

What has this got to do with sex? Well, one of the things that Christians in general and Catholics in particular believe about sex is that it isn't just a pleasure, but a peculiar way of relating to a person, incommensurate with any other way of relating. Scripture represents it as one of the primary analogies for the way Christ relates to the Church, and refers to it in both the Old Testament and the New as effecting a kind of union between the parties, referred to as a one-flesh union -- what we might today refer to as being welded into a single organism.

And if it is the spirit that gives the body its significance, then I think we get a conclusion that may seem surprising, but, to me anyway, makes a lot more sense than supposing that using our sex organs the wrong way, just as such, is the fundamental problem. Namely, we get the conclusion that the underlying problem with homosexuality lies in the mode of relationship between two men or two women, and that it is the spiritual problem in this mode of relating that makes these relationships infertile, rather than the inevitable infertility which renders such relationships wrong. If I may put it this way, two masculine souls don't fit together the right way for sex to unite them (and the same for two feminine souls), and that is what the essential problem is: the fact that two guys can't conceive a child is a sign of the problem, not the problem itself.

I said earlier that I had only an incomplete answer, and indeed that is all I have. I don't know what it is about masculine, or feminine, souls that would mean they don't fit together the right way for gay sex to ever be right; I take it that the metaphorical shape of our souls is in some way symbolized by the literal shape of our bodies, but beyond that plausible assumption -- I consider it no more than that -- I haven't a clue.

Hell if I know what's going on here.

I've heard a few explanations -- many of them extremely confident assertions of rigidly defined gender roles. I'll concede that stereotypes don't arise for no reason at all, and that they always have a basis in authentic archetypes; but I have to say that most of the explorations of gender (psychological or spiritual) that I've seen from Christian sources justify, or at best are very little better than, the skeptical and deconstructionist approaches often taken by those outside the faith in academia. Moreover, they fail even to do justice to Christian history. How would St. Francis, a grown man who refused sexual love and financial and military ambition, and who asked the Holy Roman Emperor to direct his subjects to feed the little birds, fare among the proponents of self-styled "muscular Christianity"? Or how would our contemporary worshipers of the virginal daughter becoming the obedient wife respond to St. Joan of Arc, dressing herself in men's clothing with her hair cut short and rallying men to battle? To say nothing of still stranger figures and phenomena, like St. Marina the Monk or the erotic mysticism of St. John of the Cross.**** Asserting the spiritual reality of gender, and recognizing certain of its consequences in theology and in life, should not lead us to assume that we know everything there is to know -- a hubristic and shallow approach to any question. As is the assumption that, because someone (perhaps ourselves) doesn't know something, therefore nobody knows anything.

That's as much as I've got right now. I still don't get why it's wrong -- not at a heart level -- but I have enough that I think I can accept working by faith and not by sight: again, right now. Tomorrow will doubtless have its own trouble, which will suffice it.

*The late Fr. John Harvey, on whom be peace, the founder of the Courage apostolate, is the example that springs to mind. He wrote -- and the phrase has been picked up by Dr. Joseph Nicolosi, the head of NARTH -- that "There are no homosexuals, only heterosexuals with a homosexual problem." What he meant (I think) was that the desires and dispositions of a person are not determinant of their nature; or, to put it another way, all men are fundamentally men rather than fundamentally gay or fundamentally straight; or, to put it still another way, gay men aren't a different kind of thing from straight men. Though I certainly agree that human dignity is the same for everyone and that desires don't determine what we are, I think that putting it this way is really stupid. It defies what the majority of people in fact mean by words like "homosexual" or "gay," thus putting what I consider an unnecessarily dogmatic view of terminology ahead of the basic purpose of language, communication.

**Yes, most natural law theorists -- so far as I'm aware, anyway -- are Catholics. But it's perfectly possible to be a non-Catholic natural law theorist, and vice versa: I'm given to understand that Eastern Catholicism in particular has little to no tradition of conceiving of human nature and morality in these terms. Additionally, I don't know of anyone who's made a case for a natural law theory that approves of human homosexuality as a positive good; but it's possible that someone has, or has made the attempt.

***This doesn't involve us in the belief that the reproductive system was designed with no other purpose than reproduction. That is part of why the Catholic Church concedes that natural family planning is morally licit, though of course it can be used to excess or with wrong motives: one need not be actively trying to have a baby every time, provided one is not only pursuing the other purposes of sex but also refraining from actively obstructing the reproductive purpose. But all of this is too complex to do justice to in a footnote.

****Because someone will ask, I'm not claiming (and don't think) that any of these figures were themselves gay, although depending on one's definition we could view St. Joan and St. Marina as genderqueer (with the proviso that the gender here referred to is the social aspect of gender, rather than implying that gender in its spiritual dimension was, in them, distorted in some way). I'll allow that any of them might have been gay, though I know of no evidence for it and find the question a bit of a bore -- especially in the case of St. John of the Cross, whose bridal imagery is in my opinion far more striking if he was in fact strictly heterosexual. But all of this is, at most, tangential.


  1. Gabriel, thank you for this profound article.

  2. Very interesting perspective, you write well as always. I dunno Gabriel, I can't speak for the spiritual realm but my relationship with my partner seems pretty much identical to hetero relationships. With the exception that our house is impeccably decorated it's difficult to think of any way in the physical world that our relation is different. It seems like straight relationship advice is interchangeable with gay relationship advice except for specifics in the bedroom, obviously. I also am not sure about the idea of gendered souls. Plato was a big fan, but I can't think of a specific teaching from the Church about that.

  3. Replies
    1. To Aaron and Ramuk both: It's quite true that the Church has not (as far as I know) made formal pronouncements dealing explicitly with spiritual gender. I deduce its existence, partly from my experience as an artist, partly from the distinctions that the Church has firmly maintained about the sexes (such as only ordaining men, a tradition which makes no sense at all if the only thing under consideration is sex organs), and partly from my reading "Theology of the Body," which puts the Catholic theology of the soul, I feel, into a more properly embodied and Semitic context. That being said, my own evaluation could easily be wrong in some or many respects, and even if it isn't, it's extremely incomplete.

    2. "It's quite true that the Church has not (as far as I know) made formal pronouncements dealing explicitly with spiritual gender."

      Unless I'm horribly misinterpreting, it seems like the Church has made formal pronouncements dealing explicitly with spiritual gender, in Galatians 3:27-28--"... for all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus."

    3. I think the Church has made formal pronouncements dealing explicitly with spiritual gender, in Galatians 3:27-28--"... for all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus."

  4. I'm sort of the opposite. I started life with a very strong sense, yes emotionally, that any contraceptive sex was at heart nihilistic. Indeed, the thought filled my little adolescent psyche with the dread of meaninglessness. I probably first embraced the Catholic Church for this very reason.

    Today, I can say, after a whole lot of porn and masturbation and some rare gay stuff with a guy I truly love (a love I am not hesitant to construct according to the cultural scripts of romance, as contingent as they may be) dread is quite completely numbed, and has come to be replaced by very tender feelings regarding the role of sex as expression-of-intimacy (like "grooming" behavior among animals bonding?) within a committed relationship at least (random fornication still seems drug-like and bleak to me because of how fleeting the illusion of connection is...)

    Yet I know that, deep down, these feelings all betray themselves. Because the reason THOSE particular actions are "intimate" in the first place, the reason sex involves those parts and those pleasures and that neural because they are related to having a child with someone. That's the only reason touching genitals is what sex is as opposed to, say, sticking a finger in their ear or nose. That's obvious enough. But what does it mean then when that very "organizing principle" that explains the great significance attached to the whole simultaneously excluded?

    I don't FEEL it as existential dread anymore either exactly because the emotional reality doesn't care and our secular culture is all about "experience" and relationships based on subjective chemistry.

    But deep down somewhere I still know that if I'm getting the joy (or thrill) of sharing THAT level of "intimacy" with someone, but then withholding the element which is actually what established the boundaries of intimacy in the first place...well it's like having pious feelings at a simulation of the Mass. Psychologically all the symbols (or, at least, enough) are still there to set up the dynamics of sacred and profane, the tensions needed for religious experience...but if the actual "core" that those boundaries were made for is not there, then we're just tricking our brain into having the experience through experiencing its accidents without the essence.

    I suppose what the Church needs to explore, however, is what value even accidents may have. Because I've been very prayerful at Anglican Masses; they were a farce re: transubstantiation, but does that mean they were spiritually valueless and entirely just aestheticism? Especially if as a Catholic I wasn't fooling myself and knew the limits and the difference?

    Is the Church able to recognize a similar "relative" value in loving sex acts even if ultimately still pointing out how they are morally problematic inasmuch as they pull the rug out from under their own internal anthropo-logic?

    1. I think she is, and does. The ticklish problem of divorce in this country, and pastoral responses to it, is certainly an example of the Church trying very hard to make the best of a bad situation, and trying to recognize the goods that can and do coexist with certain admitted evils. This isn't to say that her practice on this subject is not open to criticism, but I think it is an example of an attempt at what you're talking about. Nor is this phenomenon of concession and compromise unknown to Christian history -- indeed, it could claim a kind of Scriptural precedent in the whole practice of the Torah with its provisions for the hardness of men's hearts, as Christ put it, and most especially in II Kings 5.15-19, where Naaman the Syrian is given a dispensation by the prophet Elisha for a materially idolatrous act.

      The challenge, of course, is working out the details. Balancing authentic compassion and love with a rigorous commitment to holiness is always hard, not because the things are incompatible in themselves, obviously, but because our own natures always tend to find one half of the problem easier than the other. Hence, sometimes, the tendency to ask whether such-and-such a belief or precept "really matters"; the perennial tug to ignore things we find unpleasant is likely at work when we find ourselves using that phrase. Alternatively, hence the tendency to assert the importance of "speaking the truth in love," with the implication that speaking the truth is always an act of love, no matter how nastily we do it.

      I don't know whether there is a solution to the problem, at least not in the sense of "Always do X and you'll be fine." Even if there is one, I sure don't know what it is. Aside from, "Always love and follow Christ and you'll be fine," but of course, what's under discussion is the natural reply to that directive, "How?"

  5. I love you for writing this.


  6. You may be on to something in this riff on the TOB view of the body as the physical image of the spirit — both God and the individual spirit. But I'm not sure it adds anything important to the Johanno-Pauline insight that the nuptial meaning of the body is what makes it possible for man and woman to image the committed, fruitful love of the Trinity.

    1. I'm not sure it does either, but what I'm after is precisely an understanding of what, exactly, the nuptial meaning of the body consists in. Certainly it is "the gift through which all gifts are given," and one of the ways in which human beings are enabled mystically to share in one another's being, the source of all natural coinherence; and the very supernatural coinherence chose no other way to operate than through and with the assistance of the body.

      But of course, two men and two women, equally, have a pair of bodies. Why their bodies can't be nuptially united is what I'm after, considering that their love, if different in kind, can be quite as selfless and profound as the love between wife and husband. The answer to that question may well lie in a deeper understand of the Johanno-Pauline theology itself; if that's the case, I haven't swum that deep yet. This post itself may simply be me going from the edge of the river to the depth of my waist, so to speak.

  7. To take things in perspective, Gabriel, you are only what, a 6-7 year neophyte in the Church? You didn't have the privilege of having grown up in a Catholic family. Furthermore, you were abused as a child. I would not expect you to understand the morality of some things though I would entirely expect you to like to reduce the faith into a simple intellectual exercise. It's very popular nowadays but it is not of Christ.


    1. To be blunt, I haven't observed that -- in our own day and age -- being brought up as a Catholic has any great insulating effect against the errors and distortions of our culture. Admittedly I might have done better if I had had the graces of Confirmation, Confession, and the Eucharist at an earlier age; or then again, considering the lives of other Catholics (good and bad) that I've known, I might not. Given that I was raised in a Christian, though not Catholic, home, and one in which the sexual mores of Catholicism (up to and including her view of contraception) were more or less accepted, I think I got about as good an upbringing in those respects as most people have had the luck or grace to get in twentieth century America.

      As to reducing the faith to a simple intellectual exercise, well, yes, I'd quite like to do that. But I don't really see what that has to do with this. One of my chief points was that I accept the Church's teaching regardless of my ability to grasp it, and my own desire to understand is partly a manifestation of credo ut intelligam.

    2. I had to suppress a gasp after I read this. What a perfectly terrible thing to say to anyone
      As a relative once said "that is a matter for the confessional"

  8. I too find it strange how I can disagree fully with something yet still love it. The natural law does make perfect sense, especially with me being in the sciences that deal with how the human body works functionally. But maybe you are on to something. It is no secret Christians believe in the body and spirit (with rationality, emotion, will, and so forth), and that both are supposed to intertwine in a unique and special way that reflect the image of God. So to the issue of being gay or having same-sex attractions (whichever you prefer), there is naturally a physical side and a spiritual side to us. An outside observer can see the physical side of things and how they work. But there is nothing I can physically point to and proclaim as wrong (I'm a fine physical specimen if I do say so myself). The observer may instead just see inconvenient gases and curious taste of visual images (Titanic anyone?). But the observer then turns and peers deeper to the spiritual side of us and says about us humans that "there is something off about them, but in all this 'spiritual-ness' I can't quite point to it." Perhaps this is what people mean when they say"It is the result of the Fall." Our bodies began to decay, but even more devastating than that, we inherited a whole host of problems that affect our spiritual person. We then are not intertwined perfectly as we were meant to, and the whole business of sanctification is sowing the threads back together, but in a way that may bring pain, but in the end completely outdoes those original models. You've given me something to think about. Thanks for your thoughts.

  9. Thanks for this. Its very good (I'm late catching up on my reading).

    I guess natural law etc. is helpful but on a personal level I tend to prefer the "Bible says so" arguments. When God told Abraham to take Isaac to Mt. Moriah and sacrifice him, he didn't tell him why, he just told him to go.

    There is a deep coherence to the natural law tradition, but also deep problems. The distinction between "essentially non-procreative" and "accidentally non-procreative" sex acts seems counter-intuitive and arbitrary (what sense does it make to say that a woman who has had almost all of her reproductive organs surgically removed can still engage in an "essentially procreative" act, for example).

    For me personally if I'm going to be asked to do something counter-intuitive and seemingly arbitrary I'd rather be told by bibles and bishops than by Aristotle. But I understand why natural law still has deep value, especially in public philosophical conversations.

  10. I struggle with this as well, and im not catholic (im Methodist who "dabbles into" catholicism).
    My traditional roman catholic friend sees everything homo as the third way movie - comparable to alcoholism, you can change same-sex attraction.
    (Nevermind the term ssa literally feels like someone punched me in the stomach.)
    I can't make sense or turn over an argument myself (except I don't believe souls are gendered) but at the same time, my heart asks why it's wrong as well.
    And I'm going through lots of depression and suicidal thoughts, stuffI hhaven't dealt with in over a decade (26 now)

  11. Try reading my book on this topic:

    Find me on FaceBook:

  12. I think what you said about gendered souls (while maybe not the best term) is still approaching the mark. I identified as gay in my teens/early twenties and became a Christian some time later, choosing to lay down my identity to follow Christ.
    All that being said, the one thing I noticed not too long ago was that during that time, I was never once attracted to a man for *who he was*--to his soul. It was a purely a flesh thing--to use Biblical terms. To use non-biblical terms, it was only, and still is, physical. I definitely do not want to live a companionship style life with a man because I definitely don't have the attraction to a man's soul.
    One thing that's happened to me recently was that I out-of-the blue became attracted to women in a spiritual and soulish sense. And *that* arouses me. In other words, I can acknowledge a woman's beauty, but am not able to indulge in "straight porn." But when I meet a girl who acts a certain way, shares my interests, etc etc, I *am* stirred up by that and want to be around her and interact with her. And the more I grow to like her, the sexual feelings inevitably pop up to where I better have any physical contact lest I just throw myself into temptation and turn a good situation into bad.
    Anyways. I know things like these are in the hands of God and I certainly can't make them happen, but it's food for thought considering what you said about souls connecting. I can only account for my own experience and not other folks.

  13. And it's completely awesome that you used Charizard in this discussion. 10 cool points to you.

  14. Thanks for this. Your honesty and your tenacity are likewise inspiring. I'm a fledgling Catholic ally hanging onto the 'Catholic' part by a few gossamer strands... from my place of privilege as hetero, cis, and married, it's hard to imagine even speaking to this question, so I'll just say that my heart is entirely with you here. I don't have a good answer, either... just a shattering, desperate, inexplicable need for there to be a God, but only if my LGBT friends can be as wholly acceptable to Him as privileged, sheltered little Jenna could ever be.

    Peace be with you. I'm following your blog.

  15. I think the problem here has to do with art.

    You can have ten thousand precise, accurate, and sound syllogisms all proving a particular moral thesis, but if you are unable to integrate that thesis with your subconscious outlook on life, it will have a much smaller effect. That's what we* have here: Theology of the Body has made it into our minds, but not our hearts, mostly because it's alien to the way we've been taught to relate to our sexuality on a subconscious, emotional level. Quick, think about any romantic song, movie, etc that your average conservative could endorse. Even if the relationship in the art is hetero, the aspects of the relationship dwelt upon (commitment, affection, etc) would work just as well in a gay relationship. Ergo, it makes perfect sense that when we see commitment and affection in a gay relationship, it will resonate with us as "the same kind of thing" as a straight relationship, because we've been culturally primed for it. All of us.

    If we had been brought up with ToB rendered artistically, I'm sure this would be different.

    *I say "we" because even I have the same thoughts you express here, even though I'm straight.

  16. I have a question about this:

    "It is that the reproductive system is, well, a system designed with the purpose of reproduction***, and that the proper activity of rational beings like ourselves is to use things in accordance with their purpose -- or, at the very least, not use them in a way that contradicts their purpose."

    Actually, I have a lot of questions but I'll start with this one: How can we be confident that we know the purpose of some thing? I am assuming that only God is able to imbue things and acts with purpose - is that a correct characterization of your view?

    1. I wouldn't quite say that, but it's close. I'd say that, if God imbues something with meaning or purpose, that is its *objective* significance, and we disregard that kind of significance at our own peril. E.g., the purpose of eating is to nourish the body, and if we choose to exercise our free will by eating a bowlful of arsenic, we have neglected the true significance of eating and shall be accordingly imperilled, no matter what our own opinion of our action is.

      But it's clearly also true that, by our own intentions, we imbue things with meaning at a lower level (the level of personal and/or conventional, rather than intrinsic, significance). So, in chemistry, we have exercised our free wills to establish a convention that arsenic shall be known by the symbol As. This is, of course, only a convention, but its significance is not unreal; it just exists on a lower level than the deadliness of arsenic does, since it is bestowed by the image of God rather than by God.

      Now, pretty much everything we do has both an intrinsic meaning and a personal and/or conventional meaning. A toast, for example (preferably without arsenic), carries the intrinsic significance of slaking thirst, and also the conventional significance of honoring someone or something, the object so honored being determined by a personal choice. Or to take another combination of meanings, there are things that we give personal meaning to that have little or no conventional meaning, and whose intrinsic meaning may be unrelated -- inside jokes, for instance, make people laugh for reasons of the personal context, but the intrinsic and/or conventional meaning of the words doesn't communicate that meaning automatically, which is what makes it an inside joke rather than a public one.

      However, if we try to imbue something with a personal or conventional meaning that *conflicts* with its intrinsic significance, that won't work, in one way or another. That might have quite trivial or quite grave consequences, depending on many factors.

      Natural law theory would maintain (as Aquinas put it, more or less) that, if something works in the same way either always, or in the majority of cases, the thing it achieves is its purpose. (I'm oversimplifying, but that's the general idea.) This -- especially taken together with the fact that the, er, stuffs of the reproductive system, released in orgasm, only serve one biological purpose -- is held to establish that reproduction is the goal or end of the reproductive system, and correspondingly of sex.

      Many Catholics believe in natural law theory, and many natural law theorists are Catholic; and this does explain the Church's doctrine in a philosophical way, which can be helpful. But it isn't essential -- the Catholic doctrine doesn't stand or fall on natural law theory. The Catholic contention per se is that openness to life (*openness* to it, not necessarily success in producing it) is part of the inherent, God-given significance of sex, so that sexual acts which *of themselves* exclude it -- including those that take place in heterosexual sex, at least if they are wholly substituted for sex that is open to life -- are out of accord with the intrinsic meaning of sex. Aside from the natural evidence, the Church would adduce the creative pattern set out in Genesis, in which sexual differentiation is linked both to the image of God and to fruitfulness, which Genesis articulates specifically in sexually reproductive terms.