Exactly 50 years ago, as I was finishing graduate school, ready to enter the circle of historians who chronicled American religious history as a largely white Protestant preserve, my adviser introduced me to Will Herberg. Here was a Jewish-existentialist-theologian-sociologist who had just published "Protestant-Catholic-Jew." Herberg, through his classic book and his presence, planted a signpost to guide us into the pluralist understanding of the Americans' spiritual journey--and since then the effort to make sense of that journey has not ceased. Europeans, with whom so many Americans share religious heritages, are sometimes bemused to see us still going to church and synagogue, telling poll-takers that religion is "very important," and uniting to sing "God Bless America." But we are a believing people, a nation growing ever more diverse in belief and practice as the years roll on.

The American spiritual path does not resemble a straight line. Thirty years before Herberg wrote, fundamentalist and modernist Protestants squared off in conflicts like the Scopes trial, which pitched evolution against Biblical literalism. By the end of the 1940s and into the early years of the Eisenhower era, most people hardly remembered Scopes. The consuming years of the Depression, World War II and the beginning of the cold war led many Americans to put aside religious conflicts and tensions; there was enough to fight about without bringing God into the fray. They seemed content to see old battle lines among faiths erode while they religiously celebrated the American Way of Life.

Then, a year before "Protestant-Catholic-Jew" appeared, a U.S. Supreme Court decision helped trigger a civil-rights movement that had been quietly building, and a new signpost of change was planted. Faith was again politicized as it had been in the 1920s. From the fight against Jim Crow to the war on poverty to the protests over Vietnam, a broad coalition appealed to the Bible and other sacred books to justify their campaigns for social justice. On the right, believers worried about "godless communism" and, after a 1962 Supreme Court ruling, the end of prayer in schools, formed a competing camp.

So where do we stand today, five decades on from Herberg, in the first years of the 21st century?

The American spiritual journey can best be understood if we chart three of its sometimes parallel but often divergent routes.

First, most people pursue their search in traditional sanctuaries, though often in untraditional ways. Thanks to Vatican II, many walls separating Roman Catholics from other believers turned porous. Now "ecumenical" Protestants and Catholics--often joined by Jews and now Muslims and others--share prayers and work together as we saw them typically doing after 9/11. They rework traditional liturgies or sing old songs to a new beat. Many sober Fundamentalists mutate into exuberant Evangelicals, while spirit-filled Pentecostals challenge staid worshipers.

A second path takes the spiritual-minded into activism. If in the years immediately before "Protestant-Catholic-Jew" many sat back in comfortable pews, now their heirs are challenged to take political stands, pro and con. Some claim that theirs is the only true American way, and that those who take other paths must be "secular humanist" or nonreligious. The accused rail against those they call theocrats. If the midcentury revival represented an era of spiritual good feelings, in the new millennium ill feelings test the hospitable spirit that should characterize the religious quest.

The third path would have been the biggest surprise in 1955: millions speak of their being "spiritual but not religious." They shun the disorganized fronts of what they call "organized religion," and go their own way, sometimes finding new company. You will find them at retreats or book signings where the Tibetan Dalai Lama is almost as recognized a figure as the pope or Billy Graham. Devotees of alternative medicine speak of their disciplines as spiritual. To their critics these all look unmoored--reckless adventurers on stormy seas under foggy skies. The adventurers consider themselves pilgrims on solid ground, joining all the others on the paths of the never-ending, newly prospering spiritual journey, and they keep inviting more company from among their compatriots.