Many years ago, when I was an innocent lamb making my first appearance on a right-wing radio talk show, the host asked, “If you don’t believe in God, what’s to stop you from committing murder?” I blurted out, “It’s never actually occurred to me to murder anyone.”

Nonreligious Americans are usually pressed to explain how they control their evil impulses with the more neutral, albeit no less insulting, “How can you have morality without religion?” Phil Zuckerman, a professor of sociology and secular studies at Pitzer College in California, attempts to answer this question in “Living the Secular Life.” He offers an insightful mixture of academic research on shifting American religious views, his own experience as a parent, and interviews with others facing moral crises without God — from a woman overcoming drug addiction to a Holocaust survivor who bristles at the idea that God was looking out for anyone when the Nazis were murdering Jews.

Adults unaffiliated with any religion now make up nearly a fifth of the American population, but only about 30 percent of this group chose to identify themselves as atheists or agnostics in a 2012 study by the Pew Research Center. The rest described themselves as “nothing in particular,” giving rise to the media label “Nones.”

While slightly more than half of Americans say they would be less likely to vote for an atheist for president, the comparable figure in 2007 was closer to two-thirds. It is not inconceivable that the negative American image of atheists is beginning to change in a fashion that might one day resemble the dramatic shift in opinion about gay rights.