There are a few philosophers who still push the “perverted faculty argument” to prove that contraception, homosexual acts and masturbation are immoral. This argument is based on classic natural law, which is itself based on a metaphysics that assumes essentialism and teleology (broadly Aristotelian).

Because of that, it's usually not taken seriously anymore. It would still be interesting to find out if such arguments even fail at a late stage, when a lot of heavy lifting has already been done (that is, the opponent has granted all the relevant metaphysical foundations).

One version is the 40-page article by Edward Feser: In Defense of the Perverted Faculty Argument (please read at least the twelve pages of part IV. before answering, thank you).

He states his key premise (full argument on page 403f) as:

Where some faculty F is natural to a rational agent A and by nature exists for the sake of some end E (and exists in A precisely so that A might pursue E), then it is metaphysically impossible for it to be good for A to use F in a manner contrary to E.

Since he doesn't want to condemn chewing gum as immoral, he grants that using a faculty F for an end “other than” E is morally neutral.

Hence examples like chewing gum (which is merely other than, rather than contrary to, the natural end of our digestive faculties) […] simply miss the point of the argument.

But chewing gum looks strikingly parallel to masturbation. It even decreases appetite, like masturbation temporarily reduces sexual tension. The digestive system prepares for food, but no food is taken. The reproductive system of a solitary masturbating woman prepares for heterosexual intercourse (or so claims Feser), but in the end, no man has sex with her.

So to finally get to the question:

In the article, is the differentiation between “contrary to” and “other than” really meaningful? If yes, then how exactly should we understand it? If not, can you go into more details how and why the reasoning here became fallacious?

PS: I'm genuinely just trying to understand how people manage to reach such strange conclusions – no intentions to make this an “am I right?” post.

  • "In a manner contrary to..." is a somewhat antiquated expression, but the use here doesn't strike me as idiosyncratic. In context this is a use of F contrary (or opposite) to its intended end E, i.e., it's a use of F that is contrary to a use of F that produces E. Such a use would be one that interferes with the "procreative and unitive end of the sexual faculties", but may not in itself be "opposite" to E, just different from E. Similarly, one cannot speak of a "contrary child" without meaning an adult (or whatever the "opposite" of a child is meant to be.
    – ig0774
    Oct 31, 2017 at 12:06
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    The distinction seems to be of neutral vs harmful with all due vagueness in grey areas. It seems that chewing gum harms simply did not occur to him, he bites the bullet on p.406 "if someone did so mutilate the ears or nose that their function was impaired, this would not be a counterexample to the perverted faculty argument but rather exactly the sort of thing the “old” natural law theory would condemn". To me the main problem with PFA is the divining of "natural ends", whatever one's metaphysics is.
    – Conifold
    Oct 31, 2017 at 22:44
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    Let us continue this discussion in chat.
    – viuser
    Nov 1, 2017 at 3:04
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    Natural teleology is suited for a static world "created for a purpose". Evolution reproduces a surrogate of teleology but in a way fatal to any ethical applications. It is common to multipurpose and repurpose organs and behaviors, today's perversion is tomorrow's adaptation and vice versa. Who is to say that blowing off steam by jerking off is not to a "natural end". Limited time and blind manner mean that it optimizes function only locally, if that, and "function" or "fitness" are themselves ex post facto interpolations.
    – Conifold
    Nov 1, 2017 at 19:13
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    As for harm, I think the vagueness approach is promising (perhaps not for moral absolutists like Feser). We do not need to classify into black and white with exceptions, but into shades of grey. Masturbation is a trifle sin or not at all in moderation (but doctors once thought that it leads to all sorts of ailments), incest is a graver one, and chewing gum is just a bad habit. Even Feser talks about trade-offs among different ends ("the organ exists precisely for the sake of the human being as a whole"), so we end up with cost-benefit analysis on shades.
    – Conifold
    Nov 1, 2017 at 19:13

4 Answers 4


" “contrary to” and “other than” "

Surely ig0774 is correct. That something is, or can be, contrary to an aim, is an uncomplicated idea, and free of difficulty. Aristotle spoke of people who overindulged in sexual intercourse, saying they had sagging buttocks. If such buttocks are bad for riding horses in war, then over indulgence in sexual intercourse is bad for riding horses, ergo, bad for waging war, for defending the polis, and so makes the man a bad citizen.

In fact this is the tacit reasoning behind most of our so-called mental disorders. Something is normativly wrong when it is generally held to be bad for civic life. For instance, so-called "hording", which, if a man is rich, one calls maximalism, or founding a museum.... Yet, with the poor, it creates a problem for the general welfare. And so is deemed a perversion. Even in the case the individual is not yet convinced by the power of the city to determine good and evil with respect to his doings (and a supposed correlation with his brain states). Closer, and more obvious, is something like bad breath. Or, as Ovid says, not cutting the hair in the nostrils.

The chief issue is that one tends to say that these are relative to the society, so far as one has a sophisticated grasp of the issues (or, as is more often the case, if one is speaking in vague abstractions, "philosophically"), and one who meets with them naively, tends to see them in Aristotelian naturalistic essential teleological terms. I.e., that bad breath really is "contrary" to the natural aim or telos of collective social life.

  • You understand “contrary to” as “a use fostering the opposite of the aim” – for ig0774 it merely means “using it and interfering with the aim (so the aim is missed)”.
    – viuser
    Nov 1, 2017 at 4:58
  • Well, if I am not mistaken, this phrase is merely a paraphrase of the more common translation "against". If someone wants to comb their hair so that it parts on the right side, instead of the left, as it does on its own, by its innate inclination or nature, that act is against nature. Contrary to nature. That isn't always a bad thing. Training of the body is also contrary to nature. Animals don't do gymnastics. Nov 4, 2017 at 22:28
  • So "aim" means what something would do if outside influence wasn't exerted. The "aim" is not the telos, but the way of being, the so-called form. Example, the falling of stones, by nature. Lifting is therefor "contrary". The way to understand this is from the attempt to think through it the way Aristotle does, rather than giving formal definitions or merely citing examples. Nov 4, 2017 at 22:28
  • Everybody understands “contrary to” differently, here! So it wasn't that absurd to ask for a clarification, right? IMHO it simply cannot be understood as “against” (in the Aristotelian sense) otherwise a reductio ad absurdum follows instantly: “gay is not okay” => “running on a treadmill is not okay”.
    – viuser
    Nov 5, 2017 at 0:12
  • If someone is born a midget, that is the way they are by nature (congenitally), but one might say, it is not a healthy child (imagine the mother being informed, having expected a normal child), by Man as Man's (anthropos' or the human being's) nature. It's not a question of "okay", but, for Aristotle, sound judgment about what the whole is. For instance, from your claim it follows that a man born missing an arm is "okay". But, the actual opinion of most men, is that missing an arm is a defect. Aristotle is basing his thought on a empiricism of human judgment. Nov 7, 2017 at 20:44

An answer to your specifically stated question:

Yes, the distinction is meaningful. But it has to be understood within the context of the specific faculty, agent, and end. If you hold that sexual faculties have a different end than Feser's unitive and procreative ends, than you will see this argument as fallacious, especially in the comparisons Feser draws. Do you agree with Feser on the ends of the digestive system and sexual organs? If not (or if you cannot at least humor him for a thought experiment) than the comparison simply cannot be made, because he bases that comparison and the entire PFA on these assumptions about the ends of the faculties he mentions. That is why he takes the time to explain how he reaches that conclusion about the natural ends in the first sections.

There is further clarification of examples like you give (chewing gum, eating stevia) on page 408:

Yes, of course such things might be contrary to what is good for us, as even your doctor will tell you. And that is all that the perverted faculty argument is claiming. It does not follow that every frustration of a natural end is a grave sin. That depends on how crucial to the good for us as rational animals is the faculty in question is, and that is determined by such considerations as how fully it participates in our distinctively rational faculties, how significant it is to our nature as social animals, and so forth.

  • For the sake of argument, I agree that the natural end of the sexual faculties is unitive & procreative. Try to define “contrary to” – what does it mean?
    – viuser
    Nov 2, 2017 at 12:43
  • If the natural end of the digestive system is nourishment, is eating a zero calorie stevia cube immoral?
    – viuser
    Nov 2, 2017 at 13:08
  • Eating a zero calorie stevia cube can be compared, in my mind, to having sex after menopause. You are not receiving nourishment (the end of digestion) and you are not procreating (the end of sex). Neither is immoral because you are not actively "frustrating" the end. Feser talks about this on page 401 when he compares enhancing the pleasure of eating and enhancing the pleasure of love making. So eating something with no nutritional value is not immoral, but eating poison would be. Poison is "contrary" to nourishment, whereas stevia (in so far as modern science can tell) is "other than."
    – J. Tate
    Nov 2, 2017 at 13:45
  • I would argue that this is a weak distinction but I think it is strong enough to still be used and not considered fallacious. It is weak (in your example) because the lines on nourishment are not as clear cut as the lines on procreation (semen outside a vagina cannot be procreative whereas there is debate on what the benefits or harms of stevia and other foods are)
    – J. Tate
    Nov 2, 2017 at 13:46
  • PS - I was not trying to insult you or assume you hadn't read the article. This is an excellent, well thought out question. I simply meant that this distinction is indeed a weak one, but if you read all 40 pages it is hard to call it fallacious.
    – J. Tate
    Nov 2, 2017 at 13:48

There is absolutely no empirical evidence that masturbation, anal, oral sex or homosexual sex diminishes the faculty to procreate. It could even be argued that, by releasing sexual impulse in a contraceptive fashion, it can help people who are already parents to keep their offspring at a sustainable quantity, securing the long term survival of the human species, which is after all the very goal of procreation. So that is teleology for you.

Given that procreation abilities are not diminished, it can't be argued that those sexual behaviors are "contrary" to the goal of reproduction in anyway, even granting the teleological premise. They are at worst leasurly use of a natural faculty, at best, as demonstrated above, a useful complement to the goal of reproduction.

Therefore, the distinction between chewing gum and masturbation looks very much like special pleading. "Masturbation I dislike, so not ok. But if I follow my logic a lot of other popular behaviors will be forbidden as well, and that will alienate support for my position. So, they are ok, because reasons."


The perverted faculty argument says that it is perverted to use the given faculty in a manner whereby it circumvents its intended end. What Edward Feser fails to explain is that it is not the sex that prevents the conception of children after i get my vasectomy. It's the method of contraception. Further the intended purpose of sex is pleasure. If you are achieving that without perversions such as homosexuality or such you are achieving the intended purpose of sex. I would venture to say that the true perversion is what happens when a child is conceived and carried to term. Honestly if there has been a time in recent history outside of primitive cultures where it would be sane to want a child I haven't heard of it.


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