The idea that matrimony leads to children is cultural, not legal. Traditionalists would benefit if they recognized the distinction.
Musing on a new parenting study, Ross Douthat says of same-sex marriage that "the near-universal liberal optimism on the subject notwithstanding, we don't really know how straight culture will be influenced on the long run by the final, formal severing of marriage from procreation."
But why does he presume we're witnessing any such thing?
Straight marriage has long been legally severed from procreation -- that is to say, neither the ability nor the intention to have children is required, and plenty of people who marry never have kids. And even if gay marriage is legal in all 50 states, it'll be entered into by a comparatively small percentage of citizens. Meanwhile, lots of straight people will continue to marry, many of them in part to start families. It's true that we don't really know, in the long run, how straight marriage will evolve (we never have), or if gay marriage will have an effect on it; but as Americans marry and reproduce, as long as pregnancies spur marriage proposals, as long as people "wait for marriage" to have kids, the link between marriage and procreation will persist.
Is there any hint that gay marriage is going to make those behaviors disappear, or any likely mechanism by which it would do so? Anything could happen, but as best I can tell, there's no logical reason to think gay marriage will be "the final, formal severing of marriage from procreation." That's partly because, among gays, the ability to marry is likely to strengthen the tie between the two (if a lesbian couple now marries before visiting the sperm bank for a child they'll raise together, has the relationship between marriage and procreation grown stronger or weaker than in alternative world where they visited the sperm bank without being married?); but the larger reason is that neither lawmakers nor judges possess the power to sever what is a cultural phenomenon.
By battling over the definition of civil marriage as if the institution itself hangs in the balance, traditionalists have long been sending the signal that the rules laid down by the state are determinative.
They've miscalculated, for they're going to lose the gay-marriage battle. And they'll have lost precious time on the project they ought to have undertaken, given their beliefs and political reality, all along. They should've emphasized that there's long been a distinction between civil marriage and the sacrament as it is practiced in various faiths. The Catholic Church, where I was raised, distinguishes sacramental marriage in all sorts of ways. Oh, the hoops one must jump through to marry a non-Catholic in the church! And ask any priest if civil divorce procedures are sufficient to end a marriage in the eyes of God. One word, "marriage," has long encompassed secular and various religious traditions that meant varying things by it. So it shall be.
Buy gay marriage opponents keep talking about the legal fight as if once enough states permit it, America's straight people are going to react by saying, "Well, civil law is the last word on what this institution is, and it permits same-sex unions -- therefore the relationship between marriage and procreation is logically severed, and as I plan my life I shall not transgress against that logic." I don't think straight people are going to react that way. It doesn't accord with human nature as I've observed it. But if they do react that way, it'll be partly because marriage traditionalists insisted for so long that legislators had the power to irrevocably change the institution.
Only if it's ceded to them!