But some now say secularists should embrace more than the strident rhetoric poured out in books like Richard Dawkins' "The God Delusion" and Sam Harris' "The End of Faith" and "Letter to a Christian Nation." By devoting so much space to explaining why religion is bad, these critics argue, atheists leave little room for explaining how a godless worldview can be good.
At a recent conference marking the 30th anniversary of Harvard's humanist chaplaincy, organizers sought to distance the "new humanism" from the "new atheism."
Humanist chaplain Greg Epstein went so far as to use the (other) f-word in describing his unbelieving brethren.
"At times they've made statements that sound really problematic, and when Sam Harris says science must destroy religion, to me that sounds dangerously close to fundamentalism," he said in an interview after the meeting. "What we need now is a voice that says, 'That is not all there is to atheism."'
Although the two can overlap, atheism represents a statement about the absence of belief and is thus defined by what it is not. Humanism, meanwhile, seeks to provide a positive, secular framework for leading ethical lives and contributing to the greater good. The term "humanist" emerged with the "Humanist Manifesto" of 1933, a nonbinding document summarizing the movement's principles.
"Atheists are somewhat focused on the one issue of atheism, not looking at how to move forward," said Roy Speckhardt, executive director of the Washington-based American Humanist Association.
While he appreciates the way the new atheists have raised the profile of nonbelievers, Speckhardt said humanists differ by their willingness to collaborate with religious leaders on various issues. "Working with religion," he said, "is not what (atheists) are about."
The Harvard event linked up via video to a conference on global warming at the Baptist-affiliated Samford University in Birmingham, Ala.
Addressing both meetings was biologist E.O. Wilson, whose book, "The Creation," urges the faith community to join the environmental movement.
Even as he complimented the "military wing of secularism" for combating the intrusion of dogma into political and private life, Wilson told the Harvard audience that religious people "are more likely to pay attention to that hand of friendship offered to them...than to have suggested to them, let us say, Richard Dawkins' 'The God Delusion,' which sets out to carpet-bomb all religion."
In his book, Dawkins likens philosopher Michael Ruse, a Florida State philosophy professor who has worked on the creationism/evolution debate in public schools, to Neville Chamberlain, the British prime minister best known for his appeasement policy toward Nazi Germany.
The suggestion that atheists may be fundamentalists in their own right has, unsurprisingly, ruffled feathers.
"We're not a unified group," said Christopher Hitchens, author of the latest atheist bestseller, "God is Not Great: How Religion Poisons Everything."
"But we're of one mind on this: The only thing that counts is free inquiry, science, research, the testing of evidence, the uses of reason, irony, humor, and literature, things of this kind. Just because we hold these convictions rather strongly does not mean this attitude can be classified as fundamentalist."
Distinguishing between strong opinion and trying to impose atheism on others, Phil Zuckerman, associate professor of sociology at Pitzer College in Claremont, Calif., also finds "fundamentalist" a misnomer. Instead, he faults the new atheists for preferring black-and-white simplicity to a more nuanced view of religion.
"Religion is a human construction, and as such it will exhibit the best and worst of humanity. They throw the baby out with the bath water in certain instances," he said.
The Humanists are taking advantage of renewed interest in atheism--in effect riding the coattails of Dawkins and Harris into the mainstream--to gain attention for their big-tent model. According to the American Religious Identification Survey, the share of American adults who do not subscribe to any religion increased from 8 percent in 1990 to more than 14 percent in 2001.
While only a small portion of the nearly 30 million "unaffiliateds" might describe themselves as atheist, Epstein, from Harvard, sees humanism appealing to skeptics, agnostics and those who maintain only cultural aspects of religion.
A common critique of the new atheism is that it conflates belief with religiosity. In his research, Zuckerman has found that people may be outwardly religious not simply because they believe, but also because they're looking for community, strength, and solace within congregations.
More than a kinder, gentler strain of atheism, humanism seeks to propose a more expansive worldview.
"Atheists don't really ask the question, what are the vital needs that religion meets? They give you the sense that religion is the enemy, which is absurd," said Ronald Aronson, professor of humanities at Wayne State University in Detroit.
"There are some questions we secularists have to answer: Who am I, what am I, what can I know? Unless we can answer these questions adequately for ourselves and for others, we can't expect people to even begin to be interested in living without God."