"Growing numbers of Americans say they are spiritual but not religious," says Robert Wuthnow in After Heaven, his assessment of American spiritual development since 1950.

It is a spirituality without truth or authority but filled with belief in the supernatural. It is a trend born of the modern fears of religion.

The powerful critiques of Freud, Marx, and Nietzsche have penetrated our popular psyche. Freud saw religious performance as a way that guilt-ridden people cleanse themselves and force God to bless them. Marx saw religious principle used by one class of people to oppress another. Neitzsche asserted that anyone claiming to have the truth is making a power play. He asked the powerful: "Why do you call for love? Is it not just a way to keep anyone from revolting against your authority?" He asked the powerless: "Why do you call for justice? Is it not just a way for you to get on top?"

These critiques are powerful because they have the ring of truth. They're the reasons many ...