Although a Canadian sociologist, Reginald Bibby, coined the term, it has been pollster George Gallup Jr. who has most thoroughly researched its application in the United States.
At the dawn of a new century, Gallup concludes Americans "pick and choose" what they want to believe, often mixing differing ideas from within one religion or blending two or more different religions into a personal belief system.
"Substantial portions of traditional Christians, for instance, subscribe to non-Christian beliefs and practices, such as reincarnation," he said in a telephone interview.
Gallup said this individualistic spiritual questing is most obvious in recent religious history. A current of deep spiritual searching can be detected beneath even the TV evangelism excesses of the 1980s and the eclectic New Age practices of the 1990s.
"Americans are seeking something more meaningful, deeper and healthier," Gallup said. "I think it stems in part from what they perceive to be a failure of materialism in (the 20th) century and the fact that there are so many problems that surround us without apparent solutions.
"I think that's why the seeking has intensified at this point in time. The surge in this desire for spiritual growth is perhaps one of the most dramatic movements of the 20th century."
In his research, resulting from a number of statistical surveys and recounted in the new book, "Surveying the Religious Landscape" (Morehouse Publishing), Gallup reports that one cannot understand America without acknowledging the influence and impact of religion.
His work uncovers a patchwork quilt of belief and practice among Americans who profess to be religious or spiritual.
Written with D. Michael Lindsay, a consultant on theology, religion and culture, the book shows:
- More than 80 percent of Americans desire to grow spiritually.
- Church and synagogue attendance has remained relatively steady over the past 50 years.
- There is a glaring lack of knowledge about the Bible, basic doctrines and the traditions of one's own religion.
- Too often the faith professed is superficial, with people not knowing what they believe or why.
- The widespread and continuing appeal or popularity of religion.
Organized religion, in some respects, has failed to make a "profound difference in society" even though churches reach six out of 10 Americans in a given month, the book contends.
It also found some racial disparities.
Lindsay said he believes blacks have the most vibrant faith in the nation. "It has greater priority, great relevance to their lives from the research we did," he said in an interview.
"If you look at the Gallup statistics, nationwide you'll find a disparity between believing and belonging. But that's not true in the African-American community. Faith holds a primacy in their lives. If you want to reach African-Americans, you go through the church," he said.
Both Lindsay and Gallup talked about the dilemma of trying to distinguish between religiosity and spirituality in polling Americans.
"A recent poll we did showed 54 percent of Americans say they are religious, 30 percent spiritual and 6 percent both," Gallup said.
But one can only estimate the religious practice growing out of those figures.
"I have to lump the spiritual and the religious together," he said."I think the most dramatic way people are living out their faith is through volunteerism, either through faith communities or elsewhere. Almost every other person in this country is a volunteer, in terms of giving an average of three or four hours a week to some cause without remuneration."
Americans remain highly individualistic, but the researchers found many of the old distinctions that set denominations apart are blurring if not dying.
American spirituality is a polyglot, they said, in which Baptists don't all think alike. Nor do Catholics. Sometimes a Baptist may have more in common with a Presbyterian than with someone in their own denomination.
"Millions of people of all faiths are believers, many devout, but they do not always participate in the congregational lives of their denominations," Gallup and Lindsay write in the new book.
"Americans tend to view faith as a matter between them and God, to be aided, but not necessarily influenced, by religious institutions."