A couple of days ago, the New York Catholic Conference, eight bishops strong, issued a pronunciamento on same-sex marriage in response to Gov. David Paterson’s announcement that the Empire State would recognize any such marriage conducted in another jurisdiction. In expressing their unhappiness, the bishops made plain that they were not arguing on behalf of their own parochial theological or religious convictions:

Numerous theological and religious arguments could be advanced as to why same-sex unions should be rejected. However, this is not simply a matter of theology, and religious values are not the sole source of opposition to this plan.
Marriage always has been, is now and always will be a union of one man and one woman in an enduring bond. This is consistent with biology and natural law, and should be obvious to all, no matter what their religion, or even if they have no religion at all. It is a mutual personal gift between the two that serves the individual couple in many ways, allowing them to grow in love and, through that love, to bring forth children.
Just as importantly, this union also serves the larger society. Marriage provides a stable family structure for the rearing of children and is the ultimate safeguard so that civil society can exist and flourish. That is why civil society through the ages has recognized its duty to foster and respect marriage between a man and a woman.
To be clear, the state’s historic recognition of marriage is based on the biological fact that the physical union of a man and a woman tends to lead to children. Common sense and empirical evidence tell us that children’s welfare is best served in most cases by their being reared in a stable home with their mother and father. This fact has been recognized and intuited by societies for millennia. Encouraging marriage between a man and a woman, therefore, serves the state’s interests, as well-reared children who live with their mother and father are much more likely to grow to be good citizens, thereby, creating wealth, stability and security for the members of the society.

This is what’s known in the trade as a “natural law” argument, by which the Catholic Church understakes to get not just Catholics but the entire community to do what it thinks right. Now, natural law philosophy is not the simplest of academic disciplines. As my friend Mark Massa, S.J. (an historian) likes to quip: “What do you get when you cross a natural law philosopher with Tony Soprano? An offer you can’t understand.” But as the above paragraphs suggest, a natural law argument is supposed to be based on data and a process of reasoning free from revelation that any one us can engage in. Indeed, we are every man and woman jack and jill of us supposed to be able to arrive at the same conclusion.

So by rights, if the empirical data should turn out to indicate that “nature” is different from what we used to think, then we ought to be obliged to change the conclusions accordingly. For example, if it should turn out, as a matter of empirical investigation, that polygamous marital relationships and same-sex pairings are common in the human and/or animal kingdom, then the church will naturally revise its teachings. But of course only the church gets to decide what does or does not accord with “natural law.” It will not turn over that job to, say, a panel of distinguished secular historians, anthropologists, and zoologists.
All of which means that, in the public square, the natural law argument amounts to nothing more than the church giving itself permission to seek to influence public policy. Politicians take note.