Today, more than 30 percent of Americans do not believe in a personal god. No longer a hidden minority, these atheists, agnostics, and skeptics-borne from the scientific exposure and cultural mixing of the information age-have found strength in numbers. And whoever the nonbelievers in your own life may be, one thing is clear: You can't necessarily expect them to return to faith on their own. For better or worse, the societal influence of religious...