So how can those who value marriage object to offering its stability to a group that wants to marry? It’s a reasonable question. What we do know is that changing the definition of marriage from a lifelong, exclusive commitment between husbands and wives to an expression of feeling between two adults has not gone well, feelings being mercurial. Enshrining SSM furthers that redefinition.

It may be that when SSM is widely available, same-sex couples will adopt exactly the same standards about commitment and parenthood that male-female couples have traditionally practiced (and that, despite the alarming statistics, most still do). But it’s also possible that gays will bring to marriage very different expectations. Andrew Sullivan, one of the fathers of the SSM movement, has noted that gay unions are more “open” and “flexible” than straight ones. If that’s true, and surveys suggest that it is, will it affect the likelihood that married gay couples will stay together? We don’t know. Will it adversely affect any children in the home? Again, unknown.

Nor do we know whether purposely denying to children of same-sex couples a parent of each sex is damaging. Does having two fathers erase the need for a mother, or vice versa? It’s too early in the history of this experiment to know.

What we do know is that traditional families featuring the lifelong, exclusive commitment of husband and wife are best for children and for society.