(Photo: "Kissing in Lisbon" by Pål Joakim Pollen)
The Perverted Faculty argument is the central argument used by proponents of what is called (Old) Natural Law Theory (ONLT) to justify conservative sexual ethics. Typically, proponents of ONLT are Catholics (David Oderberg and Edward Feser come to mind); but this is not always the case (cf., e.g., Timothy Hsiao). The basic idea behind PFA reasoning is that our faculties have certain discernible natural ends. The end of the eye is to see, for example. The end of the reproductive faculty is to reproduce, etc. Actively frustrating these ends, so the reasoning goes, is always and everywhere immoral. Proponents of ONLT use such reasoning to rule out many sexual acts, including, but not limited to, masturbation (without finishing in coitus), homosexual acts, and contraceptive acts (including "the pullout" method). While I believe there is much to commend in the idea that the universe is chalk full of teleology, ends, and purpose -- a metaphysic presupposed by ONLT -- I believe that PFA reasoning in service of justifying conservative sexual ethics is quite weak. I explain some of my reasons for thinking this below.
In responding to counterexamples against their view, Old Natural Law Theory proponents of the Perverted Faculty Argument (PFA) make a distinction between using a faculty for something other than its natural end, and using a faculty for something against its natural end or actively frustrating its natural end. Proponents of the PFA grant that using a faculty for something other than its natural end, provided that the act doesn't frustrate the faculty's end, can be morally permissible. However, they would say that actively frustrating or acting against the end of a faculty is never morally permissible. But I've always thought that the way the distinction is appealed to in order to deflect counterxamples whilst simultaneously trying to justify the immorality of, e.g., masturbation and homosexual acts is ad hoc. I don't see why masturbating or homosexual acts are examples of using the sexual/reproductive faculty for something against its natural end rather than just for something other than its end (but not against its end). In order for PFA arguments for conservative sexual morality to work, acts like masturbation and male-on-male anal sex have to be acts that actively frustrate the end of the sexual faculty -- they can't *merely* be acts that utilize the sexual faculty for something other than its end. I can see why, for example, for a man to physically castrate himself would be to actively frustrate and indeed destroy his sexual or reproductive faculty. But I don't see how masturbation or a male-on-male sex is actively frustrating the end of the sexual faculty. One is just using the sexual faculty for something other than its end. But I don't see how one is frustrating anything here.
Feser says the following in order to justify why masturbatory acts are contrary to the end of the sexual or reproductive faculty, for example:
"Masturbatory acts involve a twofold frustration of the natural ends of sex. For one thing, they frustrate the procreative end insofar as the natural end of the physiological process in the male leading from arousal to ejaculation is not only to get semen out of the male but into the vagina, while the natural end of the physiological process of arousal in the female is to prepare the vagina for reception of semen. But these acts also frustrate the unitive end insofar as arousal is “other-directed” in a psychological sense no less than a physiological sense. Male sexual arousal is of its nature woman-oriented, and female sexual arousal is of its nature man-oriented. In each case realization of the natural end requires connecting emotionally as well as physically with another person. Masturbatory acts involve the active taking of the process of arousal to a climax that does not involve another person, and thus turns it against its natural end."
I still don't get the insistence on why masturbatory acts actively frustrate the end of the sexual faculty, rather than just being acts that use it for a different end. It's true that the natural end of sex "is not only to get semen out of the male but into the vagina," but that doesn't mean that solo masturbation (without the end of coitus) is somehow actively frustrating the end of the sexual or reproductive facutly rather than just using the faculty for something other than its natural end. And he needs the bolder claim for his argument to go through. It seems quite unmotivated to me.
Regarding his second point, coming from a secular perspective, I don't see a good reason to think that sex has such a "unitive end," which natural-law theorists ostensibly take to be realized in a unitive, comprehensive, exclusive and-open-to-children union with exactly one person of the opposite sex. That may be the view of Genesis 1/2 and Jesus, but that's difficult to maintain on a secular view of the evolutionary history of higher animals and homo sapiens, a history which seems to suggest sex is more for males to nonexclusively spread their seed as far and wide and possible, rather than for the engenderment of comprehensive exclusive unions, as poetic as that may sound. Indeed, it seems like one needs to appeal to a certain revelatory version of theism in order to justify the view that one of the ends of the sexual or reproductive faculty is exclusive comprehensive open-to-children union with exactly one person of the opposite sex. The idea that
the purpose of the reproductive or sexual faculty in humans is
reproduction seems quite plausible just from observing the world around us.
However, I think when we start talking about the aforementioned
(specific) unitive end of the sexual faculty, then one has to appeal to a
specific version of theism and indeed revelation. It's nowhere near apparent,
just from looking at our evolutionary history, that the end of the
sexual faculty is a comprehensive exclusive open-to-children union. I
think proponents of NL theory are wittingly or unwittingly sneaking
religious assumptions through the backdoor here. The idea that there's
such a (comprehensive) unitive end to the sexual faculty will only be
convincing to certain sects of religious people who already believe that
for different reasons. Muslims, e.g., don't believe that. Polygyny is explicitly allowed in the Qur'an and Muhammad had way
more than one sexual partner. In early Judaism polygny was sanctioned and widely practiced. How will the proponent of ONLT convince such people to adopt their Catholic-ish conservative secular ethics without simultaneously trying to argue for their particular religion, the truth of which will no doubt make PFA arguments moot? That comprehensive exclusive open-to-children union is an end of the sexual or reproductive faculty is simply not something that is evident to the natural light. One needs religious presuppositions to justify a robust conservative sexual ethic with PFA-reasoning. But if the truth of a religion like Catholicism is already established, then PFA reasoning becomes quite moot. So PFA arguments strike me as pretty much only convincing to people who are already predisposed to conservative Christian ethics.
Therefore, my judgement on Old Natural Law theory is that while its underlying metaphysic seems to
have something going for it, pace its proponents, the metaphysic is not sufficient, without appeal to religious doctrines, to derive a conservative sexual ethic. There's no good secular reason to believe that masturbation or homosexual acts actively frustrate the end of the sexual faculty, rather than just being acts that stimulate the sexual faculty for something other than, but not contrary to, its end.
have something going for it, pace its proponents, the metaphysic is not sufficient, without appeal to religious doctrines, to derive a conservative sexual ethic. There's no good secular reason to believe that masturbation or homosexual acts actively frustrate the end of the sexual faculty, rather than just being acts that stimulate the sexual faculty for something other than, but not contrary to, its end.
