Catholics believe that sexuality has a deep, fundamental purpose, designed by God. That purpose is procreation / reproduction. That much is obvious and need not really be defended. Everyone knows that every baby (apart from artificial insemination, etc.) comes about by a process that was initiated by sexual acts. The differences of opinion arise due to various views as to the relationship of sexuality to the mutual (and/or exclusive) commitment of human beings, to reproduction, and to natural law.
“Everyone” used to know what the Bible teaches about sexuality. Today, however, we have many people pretending that the Bible doesn’t teach certain things about sex. Since some folks with a “sexual agenda” care about the Bible, or (more accurately) the authority and legitimacy that it has traditionally granted in western civilization, they will play games and try to force it to teach what they want it to teach, rather than conform their own behavior (insofar as they accept biblical authority and its status as inspired revelation) to what the Bible clearly teaches about sexuality.
Many Christians — who are fully willing to abide by what the Bible teaches — do not understand why the Bible teaches what it does about sex, even if they accept that it teaches certain things that have been accepted in Christian cultures, to more-or-less degrees. That brings us to apologetics: my field. People are (or were until recent times) widely familiar with what the Bible and traditional Christianity (and God) hold to be wrong in the realm of sexuality, but have no clue why certain things are prohibited, and other things required.
1) The deepest and essential purpose of sex is procreation.2) Separating sex from procreation is a violation of this purpose and is against natural law.
3) Therefore, whatever does so is sinful and wrong.
1) God created sexuality for a purpose.
2) If we follow that purpose, we’re most happy and fulfilled.
3) If we deny it, then we will be unhappy and unfulfilled.
Contraception (deliberately thwarting a possible conception and engaging in sexuality under those circumstances) is wrong because it has an essential “contralife will”: it insists on separating what ought not be separated (sexuality from possible conception, or being “open” to conception). Catholics believe that a couple can space births and decide to postpone children or have no more children, for appropriately serious reasons of health, emotional factors, and finances. This is what Natural Family Planning is about. The difference is that the practicing Catholic abstains from sexuality during the woman’s fertile periods, if they have legitimate reasons not to conceive a child.
Pope Paul VI, in his landmark 1968 encyclical, Humanae Vitae, predicted several dire consequences for society and individuals, should contraception be widely practiced. They have all come true. Ideas have consequences; behaviors have consequences. He could see the bad things coming because he understood why contraception was wrong in the first place, and hence, knew that it would have terrible fruits. Now we are living with those.
The Church holds that homosexual orientation itself is not sinful. It is only when these desires are acted upon or excessively dwelt upon (lust), that it becomes sinful. In that respect it’s not that different from heterosexual non-marital sexuality. Men and women after puberty have sexual desires, because God designed it that way, in order for more children to be born. These natural desires need to be controlled and delegated to the proper place and time to find fulfillment.
The difference between homosexual and heterosexual sexuality is that the former (when acted upon in the usual ways) is, we believe, contrary to natural law in all circumstances, whereas the latter is sinful outside of marriage and a procreative will, but not sinful within those purviews.
This brings us to the deeper rationales for what is allowed and disallowed in the Christian (and specifically Catholic) view. Bluntly and generally expressed, the Catholic view is that male orgasm must occur within the act of vaginal intercourse with one’s spouse (of the opposite sex) that one is committed to for life, and that female orgasm must also be in conjunction with the overall act of love (intercourse), open to life and possible conception (i.e., no contraceptive devices or intent).
Sexual acts that are apart from this circumstance are wrong and sinful. This is Catholic sexuality in its most basic expression, or in a “nutshell.” It all has to do with commitment to one person of the opposite sex, in marriage, becoming “one” with them (as the Bible says) for the purpose of procreation and also for pleasure and closeness of the couple.
Now, why this alone is considered “proper sexuality” and other forms are not, requires much explanation, and gets into arguments from natural law and what is “natural” and what is “unnatural.” I think there are at least three ways to make this argument in an entirely non-religious, non-biblical way.
The first argument is by analogy to other organs and functions of the human body. We instinctively believe that certain things are unnatural and should not be separated. The example I use is taste buds and nutrition, in conjunction with eating. The “normal” understanding is that food should be enjoyed for its taste and also utilized for nutritional / health purposes. Both are, or should be present. We prove that this is what we believe, without thinking much about it, by our reactions to those who violate it.
On the other extreme, we have the junk food junkie. We think a person who eats exclusively Twinkies, chocolate-covered cherries, and cotton candy, or suchlike, is quite bizarre and not even remotely responsible about his or her diet. And that is because we know that food must have nutritional value, which is, in fact, its fundamental purpose, beyond merely enjoying its taste. Both have to be together. The ancient Romans used to visit the vomitorium, in which they would deliberately throw up so that they could eat some more and enjoy the pleasurable sensations of eating. They separated nutrition from food in so doing, much as contraception separates procreation from sexuality.
The second argument I have made from natural law is the analogy of bestiality as an unnatural form of sex. Even in our “permissive” day and age, it appears that most people, of whatever sexual preference, agree that this is wrong and should not be done. Again, if we ask, “why?,” we find that those who oppose it have not thought all that much about it. They intuitively or instinctively know that it is “wrong” or unnatural or obviously improper; weird, odd, bizarre, and regard those who do it as exceedingly strange and abnormal.
In the Christian view, of course, the reason is simple and straightforward: animals are fundamentally different from human beings, not being made in the image of God. But presently, we are discussing purely secular arguments. It’s not at all clear why, in a secular outlook, sex with an animal is necessarily wrong or even improper. If the end of sexuality is merely pleasure and nothing else, what would it matter how it is achieved? It’s just a sensation, like other sensory pleasures. Yet, nonetheless, bestiality is instinctively frowned upon, just as is incest: one of the few other remaining sexual taboos.In my recent paper about this analogy I even traced the laws worldwide, which are slowly but surely changing, with more permissibility of bestiality, as the world becomes more secularized. There are movements now, advocating bestiality, just as there is the notorious “Man-Boy Love” association. The analogy is clear by now, I trust. Society regards bestiality as unnatural and wrong, because, basically, it “just is.” No one feels a particular need to argue why it is wrong. Well, that is how human homosexual acts were regarded by most in society until recent times: unnatural: even by observing female and male anatomies, and how they “complement” one another.
The difference between the two, is a matter of arbitrariness (in the secular outlook). The Christian thinks bestiality and homosexual sex are unnatural. The homosexual “activist” draws the line in a different place, thinking one thing is fine and the other detestable. But it’s not at all clear to me what the essential difference is, under secularist and materialistic evolutionary assumptions.
The third argument from natural law is one having to do with the health repercussions of homosexual sex. These go far beyond simply AIDS. There are various adverse health consequences, especially as a result of anal sex, because (we would argue), acts are done that do not further the health of human beings, and run contrary to health. Activists can deny this all they want. The facts are out there and can be found in any serious online search: all the way up to a significantly lower lifespan for active homosexuals.
We argue that, “what is against natural law will in fact be unhealthy.” In terms of active homosexuality, this is demonstrable. Moreover, we know that active homosexuality (especially among males) is most often highly promiscuous. The multiplication of partners has obvious risks involved with STDs and other diseases that are contagious. The same, of course, applies to heterosexual promiscuity. All the more reason to abide by the traditional marriage to one man or woman for life view . . .
This is the nutshell presentation of the Catholic view of sexuality. Many things can, of course, be argued and defended in much more depth. I would venture to roughly guess that probably some 85% of Catholics and 99% of non-Catholics have not read about at all, let alone understood, the above reasoning and rationales.
With that level of sheer lack of knowledge, it is virtually impossible that Catholic views can be perceived in anything but a highly caricatured, stereotypical, prejudiced fashion, with all the usual silly allusions to repressed nuns and dictatorial celibate old men in red robes (and by extension, God Himself), who allegedly want everyone else to be as miserable as they supposedly are. There is very little serious discussion of these things, because in order to have that, one must first understand the fundamental premises of views other than one’s own.
Bestiality: Anti-Christian Morals Reductio? [12-21-15]
Epstein and Weinstein: The Fruit of the Sexual Revolution [11-4-17; rev. 7-19-19]
Sex and Catholics: Our Views Briefly Explained [National Catholic Register, 2-2-18]