The ideal of marriage enshrined in the 1950s reflects a myopic nostalgia for a phase that didn’t last. The 1960s brought no-fault divorce, which allowed wives as well as husbands to dissolve their bonds without proving some terrible transgression by the spouse.

This was an earthquake, causing unprecedented numbers of unions to collapse. A writer for the conservative Family Research Council said that under no-fault divorce laws, marriage became “nothing more than notarized dating.” Maggie Gallagher of the National Organization for Marriage said their effect was nothing less than “the abolition of marriage.”

In a sense, she’s right. But you don’t see many conservatives trying to repeal no-fault laws in the name of “traditional marriage.” Gallagher misses the more fundamental point: This institution is not something passed down unaltered from generation to generation, like the family silver. It is continually in flux, taking forms that would surprise our forebears.

Marriage, like transportation, has always been a part of human existence. But riding a donkey is very different from flying in a jet, and modern marriage has only superficial similarity to what went before. Just as we embrace each new mode of travel that enhances human welfare, no one should mind adapting marriage to the needs of modern people.