Some Thoughts on Hsiao’s Perverted Faculty Argument

Some Thoughts on Hsiao’s Perverted Faculty Argument August 24, 2019

The Perverted Faculty Argument (PFA) is a strand of Thomistic (Thomas Aquinas) thinking that is intertwined with Natural Law Theory (NLT)  of which I have been blogging lately. I was challenged by Vincent Torley recently to, if I was going to attack the PFA (as I have done here and here), attack the best form of the argument. The claim was that Hsiao’s defence was the best. It can be found here.

Hsiao introduces the argument as follows:

There is an old argument rooted in the classical natural law tradition that says that the “perverse” or “unnatural” use of a human faculty is immoral. This short essay offers a derivation, overview, and brief defense of this “perverted faculty” argument (PFA). I shall argue that the PFA is entailed by some commonsense theses about the nature of goodness.

I take as my starting point a claim famously defended by Peter Geach in his paper “Good and Evil.”1 Geach argued the meaning of “good” and “bad” depends on something’s nature or function. In other words, we cannot know whether something is good or bad without first understanding its nature or function. This account of goodness does not originate from Geach, but dates back to Aristotle and has recently been the subject of renewed attention amongst recent philosophers.2 The contention of this paper is that the Aristotelian thesis entails the PFA, or at least something very much like it.3

If I am right, then advocates of eudaimonistic ethics should take the PFA a lot more seriously.

The Argument

The PFA can be derived as follows:
(1) For any x that is a K, if x is good, then x is a good K.
(2) If x is a good K, then x is good by being as Ks ought to be.
(3) Therefore, if x is a good human action, then x is good by being as
human actions ought to be. (From 1–2)
(4) Human actions ought to be aimed at human goods that are proper to
(5) Human goods are that which fulfills human faculties.
(6) Therefore, human actions ought to be aimed at that which fulfills
the human faculties that are proper to them. (From 4, 5)
(7) Therefore, if x is a good human action, then x is good by aiming at
that which fulfills the human faculties that are proper to it. (From
Although the PFA is best known for its implications in applied ethics, my focus will be mainly on whether the PFA can be derived from an Aristotelean conception of goodness, and not so much its practical applications. Others have addressed its significance for specific moral issues elsewhere.4

In this piece, I will lay out Ficino’s initial thoughts on the paper. He, a regular commenter and contributor here, has something of a deep interest in Thomistic thinking and critiquing it. His notes are as follows. I hope to make my own comments on it in due course. There will be talk of sex and sexuality – don’t be prudish!

1. One organ can be an instrument for more than one faculty (e.g. Aristotle talks about this in De Anima), and Ari says nature is economical. I see no reason to accept e.g. the following of Hsiao”s: “An act that, for example, involves the use of the faculty of procreation must respect its function by directing its use toward a goal that is fitting for the end of procreation” (p. 212). This assumes that every use of our naughty bits is an actualization of the faculty of reproduction. I don’t think he’s given reason to accept this. It’s not obvious that, say, a woman stroking her clitoris and experiencing pleasure and relaxation is directing her faculty of reproduction at all.

2. Our higher natural faculties, spirit/emotion and intellect, as Hsiao acknowledges, can override lower ones in directing use of organs: e.g. your hands instead of your mouth when you are speaking American Sign Language. You use your hands for an end toward which they are not intended (speech) and restrain your mouth from serving one of its natural faculties to achieve a natural end for humans (speech).

3. He doesn’t consider activities that are ends in themselves vs those that serve ends, and higher ends of higher parts of soul trumping lower ones, e.g. intercourse to serve a relationship of love AND done so as to achieve the natural end (cf. Politics VIII.5-6) of limiting family size together trump the end of pumping out another kid.

4. Hsiao equivocates on terms like “ought.” cf. p. 212 “That is, the term “ought” in the fourth premise should be understood as expressing both a teleological and moral ought.” I think his attempts to support this cobbling together amount to assertion more than demonstrating that his “ought” is legitimately derived from his “is.”

5. He tries to stitch deontology into his eudaimonistic ethics, e.g. p. 213 “There is a difference  between failing to realize a goal toward which you are already aiming, and failing to aim toward a goal that you should be attempting to pursue,.”  or p. 214 “It is wrong to misuse our faculties.” Eudaimonistic ethics would come at an issue from whether you harm or care for your soul, rather than from what rule you are obligated to follow. Hsiao’s analysis seems to blend these in a confused and perhaps sophistical way.

Thanks to Ficino for these intitial thoughts. More to follow!



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