Yes, suggests Jody Bottum, in a Commonweal article that has roiled the right-wing Catholic intelligentsia. That the former editor of First Things should go wobbly on marriage was bad enough. That he would enlist the patron saint of Natural Law Catholicism in his betrayal was nothing less than outrageous.

Here's how Bottum puts it:

Too careful, too honest, simply to condemn everything except the sanctified monogamy that Christianity had given him, Thomas works through an escalating series that ends up preferring the Christian idea of nuptials as the richest, most meaningful form of marriage—without condemning even polygamy as necessarily a violation of the most philosophically abstract application of the natural law. In this, I think, is a model for how Catholics might think about the world in which legal recognition of same-sex marriage has emerged.

Let's take a closer look. Thomas considers the issue of polygamy in Question 65 of the Supplement to his Summa Theologica. Is it, he asks, against the natural law to have several wives?

Marriage has as its principal end "the begetting and rearing of children," and having more than one wife works in that regard. True, polygamy may hinder achievement of marriage's secondary end -- providing a satisfying and harmonious family life (given one husband's inability "to satisfy the requisitions of several wives" plus the greater likelihood of familial strife -- but it does not "wholly destroy" that end. Finally, for Christian believers, polygamy removes the third end of marriage, which is to signify Christ's relation to the Church.

Thomas' conclusion: "It is therefore evident from what has been said that plurality of wives is in a way against the law of nature, and in a way not against it."

How would this work, mutatis mutandis, with respect to same-sex marriage? If SSM doesn't provide for the begetting of children, it certainly provides for their rearing -- and, as Thomas makes clear in Question 41, Article 1 ("Whether matrimony is of natural law"), it is not the begetting but the education and development of children that constitutes the core purpose of the institution.

Regarding the secondary end of of marriage, SSM offers the partners the kind of family life -- and "the mutual services which married persons render one another in household matters" -- that Thomas, good Aristotelian functionalist that he was, understood as required by human nature. Likewise, SSM provides the one-on-one relationship that can, for Christian believers, signify Christ and the Church.

To be sure, Thomas lived in an age that had a narrower understanding of gender roles than we do; he himself saw household work in gendered terms. But what's perhaps most notable about his discussion of human affairs is his recognition of the variety of human experience, and hence the legitimacy of different social norms. Asking "whether it was ever lawful to have several wives," he points out that "human acts must needs vary according to the various conditions of persons, times, and other circumstances."

In short, unlike his latter-day epigones, St. Thomas saw in natural law not a code of conduct but (up to a point) an enabler of cultural relativism. SSM would, I agree, not have thrown him for a loop.