Once a week, atheists Lex Bayer and John Figdor met at coffee houses around Stanford University in Palo Alto, Calif., to work on their book about how to lead a happy and moral life without religion or a belief in God.

Debate often flared as they picked through such heady concepts as how to define reality, choose the right way to behave and ponder whether there is life after death. They also talked about their individual experiences of losing religion.

“Patrons would come up to us and want to talk about these things with us,” said Figdor, the humanist chaplain at Stanford. “These are things they are grappling with in their lives, things they care about, even if it’s not something they are used to discussing.”

Their new book - “Atheist Mind, Humanist Heart: Rewriting the Ten Commandments for the Twenty-first Century” (Rowman & Littlefield Publishers, $32, 188 pages) - is a result of those coffee house discussions. It also addresses what the authors see as a need among a growing number of Americans to talk about their beliefs when they don’t believe in God or aren’t comfortable with religion.

“We’re not anti-religious, and we’re not trying to push our nonbelief in God onto others,” said Bayer, a South African-born entrepreneur and board member of the Humanist Connection, a nonprofit serving Stanford and Silicon Valley. “We’re giving people a way to ask, where do your morals come from, and how do you justify your beliefs?”

Helping people devise their own commandments - the 21st-century commandments of the title - offers a rational framework for self-reflection, the authors say.

They also invite people to share their commandments by entering their Rethink Prize, a crowdsourcing contest with $10,000 in prizes that closes Nov. 30. (Find details at www.atheistmindhumanistheart.com.)

Born Jewish, Bayer began to question God’s existence as a teenager. Figdor’s interest in Christianity began to wane sooner, as an 8-year-old learning Santa Claus wasn’t real. By 14, he had abandoned his faith altogether when he failed to find answers in the Bible for why the Holocaust happened. Figdor says he was left to ask, “Now what?”

Their book comes as national data from the Barna Group, an evangelical Christian polling firm, found that one-third of Americans are “secular in belief and practice.” This 2014 study follows 2012 Pew Research numbers showing that one-fifth of the U.S. public, and one-third of adults under 30, say they have no religious affiliation.

Even the numbers of people who identify as agnostic or atheist is growing, the Pew study showed, up from 4 percent in 2007 to 6 percent in 2012.

Figdor wonders if the actual number of agnostics and atheists is higher. “People are not comfortable being identified as atheist or agnostic,” said Figdor, who later earned a master’s degree at Harvard Divinity School. “There is still the stigma.”

Both are aware that atheists are often seen as immoral. Rejecting God and church has long been synonymous with wickedness. People may also associate atheism with famous contrarians like the late journalist Christopher Hitchens or evolutionary biologist Richard Dawkins, who, respectively, challenged the saintliness of Mother Teresa and called a belief in God a “pernicious” delusion.

Judging from a 2012 Gallup poll asking which groups they would accept as president, Americans have become more tolerant over the past couple decades - except when it comes to atheists. Only 53 percent of respondents said they would vote for someone who doesn’t believe in God - behind every other group, including women, Catholics, Mormons, gays, lesbians and Muslims.

Bayer and Figdor want to emphasize atheism’s “humanist” values. A humanist, they say, is someone who believes in the goodness of human beings and seeks rational ways to solve human problems.

Their book is set up as a series of steps that lead readers through the basics of using inductive reasoning and classic philosophical approaches. Bayer and Figdor also offer up their own version of the 10 commandments, which they call their “non-commandments.” Their non-commandments, which include the belief that people can use rational thought as a tool for understanding the world, led both to conclude there is no life after death. “Some people might say ‘I don’t know’ is a more appropriate answer, since I’ve never experienced death,” Figdor says. “I’ve never encountered a mind without a brain. So if the brain dies, it’s reasonable to assume the mind that lives in that brain dies with it.”

For those who fear this approach gives rise to a dangerous moral relativism, Bayer and Figdor say humans operate out of “enlightened self-interest,” which teaches them they are more likely to be happy and get what they want if they cooperate. Humans also are biologically hard-wired to be empathetic and be interested in the happiness of others.

“I take pride in conducting my life in a moral manner and in my ability to derive happiness from the happiness of others,” Bayer says. “I feel good when my friends think of me as a person of high morals and integrity.”