Prostitution is rarely considered a good thing. Even most who advocate strongly in favor of the freedom to prostitute oneself for money would agree that actual prostitution usually leads to undesirable effects. (There are some who would resist this, of course, but they’re probably in a very small minority.)
One person who falls in the middle camp—i.e., reluctant toleration for prostitution—is none other than the Christian thinker, Thomas Aquinas. Renowned for his defense of virtue and a moral theory grounded on natural law, Aquinas is also strangely famous (at least to some) for his insistence that, although prostitution is gravely wrong, we ought not to do anything to forcibly and legally prevent it.
This raises an obvious question: if something is demonstrably unhealthy—and especially if it is clearly, morally wrong—don’t we have an obligation to forbid it?
Aquinas’s stance on prostitution, taken mainly from articles in the secunda pars of the Summa Theologiae, is finely nuanced. And it offers a wonderful chance to reflect on precisely what are the obligations that a society faces with respect to defending human dignity, and to promoting the common good.
It’s worth noting, that Aquinas’s position relies on the fact that prostitution is simply a type of fornication. The latter, he believes, is contrary to the natural moral law precisely because it diminishes the value of sexual intimacy by failing to provide a suitable institution for the rearing of children (cf. ST IIa-IIae, q. 154). Since the possibility for procreation is naturally entailed in moral sexual encounters, according to Aquinas, then entering into such a relationship outside its proper context (i.e., marriage) is a violation of its natural order.
The implication, then—since fornication does damage to natural goodness, including the dignity of human persons—is that fornication should be opposed. Morally speaking, this certainly means refraining from extra-marital sexual relations, and encouraging others to follow suit.
But is this moral opposition to fornication—and by extension, prostitution—something we ought to effect in law?
Aquinas responds in the negative. According to his theory of human action, there is a distinction between interior and exterior actions: an interior act is one concerned with intention, knowledge, etc.; while an exterior act is one recognizable and present to outside observers. Civil law is concerned only with the latter (cf. ST Ia-IIae, q. 98), as its goal is to preserve temporal balance, and not to achieve full justice vis-à-vis interior dispositions. In the case of fornication, then—since sexual intercourse is naturally good, and it is only the manner of its occurrence that is evil—it is beyond the reach of civil law to forcibly prevent people from engaging therein.
As far as prostitution is concerned, the same principle applies: namely, that civil law should not be concerned with preventing prostitution, since the external act itself is not suspect, and does not inherently endanger temporal balance and well-being. (To be fair, Aquinas does mention a rather strange passage from Augustine’s De ordine, that “If you do away with harlots, the world will be convulsed with lust.” But this has less to do with condoning prostitution for the sake of purity than it does with sustaining the idea that too much civil crack-down in interior matters can actually serve to endanger desirable goods, and chiefly the good of reform and conversion.)
At bottom, Aquinas’s peculiar “defense of legalized prostitution” introduces a set of distinctions that’s invaluable for navigating public policy debates even today. A popular tendency amongst those who whole-heartedly oppose things like prostitution, pornography, marijuana use, and other similar “Category B” social ills, is to say—almost without thinking—that they ought to be outlawed. I don’t suppose that we can or should treat each of these phenomena equally. They’re very different, and perhaps some should be outlawed. But assessing each of them from the perspective of the role and duties of civil law is a great place to begin understanding just why that’s the case. (After all, there must be a reason why those who wish to outlaw prostitution aren’t pushing for jail time for fornicators, or fines commensurate with lustful thoughts.)
In the end, appreciating the authentic place of human law for ensuring and promoting the common good helps us to balance our hope for a just, civil society with the reality that what we’re working with are broken and imperfect people. Part of attaining the highest good, as Aquinas rightly points out, is allowing room for that good to develop somehow organically. And at the very least, overly oppressive and invasive civil laws do not aid in achieving that end.