How many atheists are there?

It depends on your definition of the term. Only between 1.5 and 4 percent of Americans admit to so-called "hard atheism," the conviction that no higher power exists. But a much larger share of the American public (19 percent) spurns organized religion in favor of a nondefined skepticism about faith. This group, sometimes collectively labeled the "Nones," is growing faster than any religious faith in the U.S. About two thirds of Nones say they are former believers; 24 percent are lapsed Catholics and 29 percent once identified with other Christian denominations. David Silverman, president of American Atheists, claims these Nones as members of his tribe. "If you don't have a belief in God, you're an atheist," he said. "It doesn't matter what you call yourself."

Why are so many people leaving religion?

It's primarily a backlash against the religious Right, say political scientists Robert Putnam and David Campbell. In their book, American Grace, they argue that the religious Right's politicization of faith in the 1990s turned younger, socially liberal Christians away from churches, even as conservatives became more zealous. The dropouts were turned off by churches' Old Testament condemnation of homosexuals, premarital sex, contraception, and abortion. The Catholic Church's sex scandals also prompted millions to equate religion with moralistic hypocrisy. "While the Republican base has become ever more committed to mixing religion and politics," Putnam and Campbell write, "the rest of the country has been moving in the opposite direction." As society becomes more secular, researchers say, doubters are more confident about identifying themselves as nonbelievers. "The collapse of institutional religion in the first 10 years of this century [has] freed so many people to say they don't really care," said author Diana Butler Bass.

How are nonbelievers perceived?

Most polls suggest that atheists are among the most disliked groups in the U.S. One study last year asked participants whether a fictional hit-and-run driver was more likely to be an atheist or a rapist. A majority chose atheist. In 2006, another study found that Americans rated atheists as less likely to agree with their vision of America than Muslims, Hispanics, or homosexuals. "Wherever there are religious majorities, atheists are among the least trusted people," said University of British Columbia sociologist Will M. Gervais. As a result, avowed atheists are rare in nearly all areas of public life. Of the 535 legislators in Congress, for example, only one — Rep. Pete Stark (D-Calif.) — calls himself an atheist. Few sports stars or Hollywood celebrities own up to having no religious faith.

Why so much distrust?

Many Americans raised in the Judeo-Christian tradition are convinced that atheists can have no moral compass. Azim Shariff, a University of Oregon psychologist who studies religious thinking, sums up how believers view nonbelievers: "They don't fear God, so we should distrust them. They do not have the same moral obligations as others." The antipathy may have actually grown with the recent emergence of "New Atheist" writers such as Richard Dawkins and the late Christopher Hitchens, who have launched impassioned attacks on organized religion. Dawkins has encouraged his followers to "ridicule" anyone who could believe in "an unforgiving control freak" and "a capriciously malevolent bully" like the God portrayed in the Old Testament. Dawkins's harsh approach, said Barbara J. King, an anthropologist at the College of William and Mary, has confirmed "some of the negative stereotypes associated with the nonreligious — intolerance of the faithful, first and foremost."

How have atheists responded to this negative image?

A coalition of nonbelievers is out to make atheism more acceptable, starting with last month's "Reason Rally" on the National Mall in Washington, D.C., where thousands stood up for their right to not believe. Silverman of American Atheists, who helped organize the rally, said it was intended to give heart to young, "closet atheists" who fear the social stigma of being "outed," in much the same way closeted gays do. "We will never be closeted again," he said. Some within the movement advocate taking a more conciliatory approach to believers, too. Alain de Botton, the Anglo-Swiss writer of the new book Religion for Atheists, assails Dawkins as being "very narrow-minded," and praises religions as "the most successful educational and intellectual movements the planet has ever witnessed."

Will atheism ever be accepted?

If growth continues at the current rate, one in four Americans will profess no religious faith within 20 years. Silverman hopes that as nonbelief spreads, atheists can become a "legitimate political segment of the American population," afforded the same protections as religious groups and ethnic minorities. But he's not advocating a complete secular takeover of the U.S. — nor would he be likely to achieve one, given the abiding religious faith of most Americans. "We don't want the obliteration of religion; we don't want religion wiped off the face of the earth," Silverman said. "All we demand is equality."

Atheists in foxholes

Atheists are barely visible in politics and entertainment, but they are clamoring for recognition in another area of public life — the military. The Military Association of Atheists and Freethinkers estimates that 40,000 soldiers identify as nonbelievers, and counts the most famous casualty of the war in Afghanistan, former NFL star Pat Tillman, as one of its own. In attempting to secure the same rights and support enjoyed by religious soldiers, the association lobbies against the idea that "there are no atheists in foxholes," and wants "atheist chaplains" made available for the ranks of the armed nonbelievers. Jason Torpy, the association's president, says that nonbelievers outnumber every religious group in the military except Christians, yet receive no ethical and family counseling geared to their own nonbeliefs. "These are things that chaplains do for everybody," he said, "except us."