In May of this year, after a Florida jury convicted 14-year-old Nathaniel Brazill of fatally shooting a schoolteacher, people shook their heads and asked the question that was previously pondered regarding Columbine killers Eric Harris and Dylan Klebold: "Where were his parents?" The question implies a value judgment—that good parents would raise children well enough to know that you do not resolve disputes with teachers by murdering them.

Killing the innocent is everywhere condemned. Murder is considered malum in se—that is, evil in itself. Everyone should know it is wrong, even if they are unaware of a particular law against it.

But how does "everyone" learn what is wrong? We enter the world armed with what James Q. Wilson, in his memorable book of the same title, labeled "The Moral Sense." But, says Wilson, that sense is no more than a yearning for rules, a need that must be filled. For Christians, however, the act of raising a child is, in large measure, a process of fulfilling that child's God-given desire for moral knowledge. In short, everybody knows that killing the innocent is wrong because every child is taught that lesson from an early age.

Who does this work of moral teaching? We begin, of course, with the family, which is why all the people who wondered about Brazill's parents were asking the right question. But parents do not act in a vacuum; they act in a culture. And the culture sends its own messages. When those messages are in competition, rather than cooperation, with what parents try to teach, we can predict trouble.

In the literature on moral education from two generations ago, one occasionally would come across the metaphor of the three-legged stool. Morality, it was said, was taught to children ...