By the 1920s, with science and industry humming along, Spiritualism had given way to a new movement called New Thought. New Thought was tethered to an appealing concept: The human mind was capable of delivering anything it desired, from pain relief to debt relief.

That message was appropriated by others who wanted to tap into the frustrations of the masses."The get-rich philosophies that followed, like Norman Vincent Peale's classic, The Power of Positive Thinking, all were the result of the changes in economics," Fuller says. "In the 1800s, it was relatively straightforward. The harder you worked in the field, the more successful you were.

"But with the advent of the stock market in the new century, people suddenly felt like they had less control of their lives and of success. So along come these people saying 'You just need to change the way you're thinking,' and believe me, that hit home." Today, you need only to see Donald Trump's face beaming from a Learning Annex brochure to know that the appeal of this promise remains irresistible.

But there are plenty of people who see positive thinking as a deeply religious experience that can help connect humans both to each other and a higher power. New Thought leader Trapp says his organization hopes to welcome this group.

"Many people seem to be looking for this philosophy now but just don't seem to be aware of who we are," says Trapp. As for The Secret, he appreciates any spillover into the pews but advises fans to be informed.

"It is a good introduction, but (the book) is superficial and tends to focus on accumulating material things," he says. "That is only the beginning of the message. The real point of mental power is to create a world that works for everyone, with food, education and health care for everyone. I'm glad (Unity) ministers are using The Secret to try and bring people in. I just hope it segues for many people into a church experience."

Interestingly, the president of the New Thought Alliance, Blaine Mays, questions whether the book's popularity can translate into new believers for Unity or other metaphysical churches. "Maybe one in 100 will ask, 'I wonder if there's a church that preaches these same ideas,' " Mays says. "Face it, you had Transcendental Meditation, you had Shirley MacLaine, now you've got The Secret. You just know it also won't be around forever."

Mays thinks the "spiritual aspect" of New Thought turns off those mainly on the hunt for a salary increase or a better love life."We're not against that, but it's just that it's not what we're really after," he says.But the pursuit of material happiness is just fine with some New Thought leaders, including Lett, who says, "God never said it wasn't OK to be well fed, well clothed or drive a nice car. You have to take care of yourself, as well as others."

Mark Anthony Lord, minister at Chicago's Center for Spiritual Living, echoes that sentiment. "America was built on having a wonderful life, on being all that you can be," he says. "If you generate a feeling of self that's capable and worthy, you'll attract what you want. I don't care if you use it to get a car."

Attendance is up at his center since The Secret caught fire, which pleases Michelle Schrag, who attends each Sunday with her stockbroker husband and three children. Though raised Catholic, Schrag says the center's "emphasis on meditation, which I now do each day, has helped me find happiness in my daily life."

Schrag is typical of a growing breed of American who declares, "I'm spiritual, but not religious," says Catherine Albanese, who heads religious studies at the University of California-Santa Barbara and is author of A Republic of Mind and Spirit: A Cultural History of American Metaphysical Religion.