On March 26, the U. S. Supreme Court heard oral arguments in a case challenging California’s “Proposition 8”—the state constitutional amendment defining marriage as the union of one man and one woman that was adopted by voters in 2008.

Perhaps the roughest moment for Charles Cooper, the attorney representing the proponents of Proposition 8, was when Justice Elena Kagan challenged the argument that marriage exists to promote procreation by spinning a hypothetical question about a couple where the man and woman are both 55 years old, and thus unlikely to procreate.

The (mostly liberal) audience laughed—either unable or unwilling to understand Cooper’s answer, which was actually quite cogent. He began by noting, “It is very rare that both parties to the couple are infertile,” but Kagan cut him off with another question about the couple (rather than the individuals) involved.

Cooper again went on to explain:

Your Honor, society’s . . . interest in responsible procreation isn’t just with respect to the procreative capacities of the couple itself. The marital norm, which imposes the obligations of fidelity and monogamy, Your Honor, advance the interests in responsible procreation by making more likely that neither party, including the fertile party to that [marriage, will procreate outside the marital relationship].

Except the last part, in brackets, Cooper did not actually get to say, because he was again cut off.

Perhaps Cooper was wary of appearing sexist to Justice Kagan if he stated the truth more bluntly—55-year-old women are virtually always infertile, but 55-year-old men are not. As frustrating as it may be to some feminists, there are some sex differences which cannot be overcome. (Justice Antonin Scalia tried to save Cooper with a joke about Strom Thurmond, the late U.S. Senator who continued to father children well into his 70’s, but it seemed to go over the audience’s heads.)

Society’s interest in promoting “responsible procreation”—the term most commonly used in defending marriage as the union of a man and a woman—involves not just promoting procreation itself, and promoting it in a responsible context (i.e., where the mother and father who make a child are both committed to the child and to each other through marriage). “Responsible procreation” also implies an effort to discourage irresponsible procreation—a quite plausible example of which might be a 55-year-old man going around impregnating fertile women (presumably younger than himself) who are not his wife.

Advocates for redefining marriage really ought to listen more, and laugh and scoff less—especially when they are in the Supreme Court of the United States. Otherwise they make themselves, not their opponents, look ignorant.