The Supremes have given us a surprise, in a good way for once.

In a move that may signal the inevitability of a nationwide right to same-sex marriage, the Supreme Court on Monday let stand appeals court rulings allowing such unions in five states.

The development, a major surprise, cleared the way for same-sex marriages in Indiana, Oklahoma, Utah, Virginia and Wisconsin. Officials in Virginia announced that marriages would start at 1 p.m. on Monday.

The decision to let the appeals court rulings stand, which came without explanation in a series of brief orders, will almost immediately increase the number of states allowing same-sex marriage from 19 to 24, along with the District of Columbia.

They’re doing it this way on purpose, apparently. Letting things play out before ruling.

There may then be no turning back, said Walter E. Dellinger III, who was an acting United States solicitor general in the Clinton administration.

“The more liberal justices have been reluctant to press this issue to an up-or-down vote until more of the country experiences gay marriage,” he said. “Once a substantial part of the country has experienced gay marriage, then the court will be more willing to finish the job.”

There is precedent for such an approach. The court waited until 1967, for instance, to strike down bans on interracial marriage, when the number of states allowing such unions had grown to 34, though it was still opposed by a significant majority of Americans.

Popular opinion has moved much faster than the courts on same-sex marriage, however, with many Americans and large majorities of young people supporting it.

Let’s have a round of applause for Mad About You and Will and Grace and Modern Family.