The facts also support a basic conservative belief: that it is difficult for teens to be moral alone. Wilcox argues that teen sexual behavior can be influenced -- that teenagers can be more than the sum of their hormones. But responsible behavior requires both "norms" and "networks." An intellectual belief in right and wrong is not sufficient. Teens require a community that supports their good choices, especially in times of testing and personal crisis. "Kids who are embedded in a social network with shared norms," he concludes, "are more likely to abide by them."

Sociologist Peter Berger calls these networks "plausibility structures" -- sources of authority that do more than lecture or shame; they define the meaning of common sense. When institutions such as religious groups, families, government and the media send a strong and consistent message -- smoking is stupid, driving under the influence is criminal, teen pregnancy is self-destructive -- we have sometimes seen dramatic changes in behavior. Teen pregnancy and birth rates in the United States, for example, have declined by about one-third since the early 1990s.

These messages of responsibility are often reinforced by tight-knit religious communities, but they are not owned by them. Wilcox notes that American liberal elites often "talk left and walk right, living disciplined lives, and expecting their children to do the same, even when they hold liberal social views." Divorce rates among college-educated Americans, he points out, have fallen since the 1980s, as it became more evident that casual divorce did not serve the long-term interests of their children.

The decisive role of authoritative communities in determining individual behavior should not surprise conservatives. Conservatism teaches that individuals are not inherently good and so must be carefully civilized. They need social structures and networks that foster duty and discipline and define those commitments as common sense. In "The Quest for Community," Robert Nisbet warned: "Release man from the contexts of community and you get not freedom and rights but intolerable aloneness and subjection to demoniac fears and passions."

It would be nice if teen sexual behavior could be automatically changed by an abstinence lecture or a sermon. Setting those norms and expectations, however, is a small part of a larger cultural task. Moral men and women need moral communities.