LAST Valentine’s Day, Justin Murray and Sarah Kinsella sent out more than 800 pink greeting cards, one to every female freshman at Harvard. The two seniors stayed up nearly all night, taping candy hearts to the notes, which read: “Celebrate love, celebrate life, celebrate you: Why wait? Because you’re worth it.”

Founders of Harvard’s new abstinence society, True Love Revolution, Ms. Kinsella and Mr. Murray have been going out for a year and a half.

On a recent date at Border Café, a Mexican restaurant in Harvard Square, they sit on the same side of the booth, linking fingers and stroking each other’s hair.

This is about the extent of their physical connection. “We don’t push it,” says Ms. Kinsella, sipping a lemon-lime Margarita. “We pretty much stick to kissing and cuddling. At night, Justin will walk me back to my room, and we’ll hang out for a little while. I’ll give him a back rub or something, but, yeah, then he heads back to his dorm.”