Marriage remains a perennially popular institution—otherwise why would same-sex couples be clamoring to share in it?—and yet after the first bloom of love fades, marriage faces an inherent problem. You have to hammer out a life with another person who may not find it particularly easy to hammer out a life with you. Many couples work out what to do on their own. But what should clashing couples do?

Marriage counseling became a popular answer to that question after marital referees...