Sometimes the current state of the moral universe is best glimpsed not in philosophical treatises but in flashes of light thrown off by ordinary speech. For example, I was brought up short recently by a casual comment made by a friend, a conscientious and thoroughly admirable mother of two young children, who remarked to me that in her household, the words “should” and “shouldn’t” were regarded as four-letter words, impermissible to utter. I was struck by this statement, but since she moved right along to talk about all the ways she was trying to improve her kids’ diet, my first thought was to dismiss her striking formulation as a mere passing fancy rather than a settled conviction. But I couldn’t help but wonder to myself: didn’t her words mean, strictly speaking, that the only moral proscription that she was conscious of imposing on her children and herself was the requirement they not impose moral proscriptions on themselves or others? That the only rule was to have no rules? Is that really what she meant?