In the public school I went to in the 1970s, "secular" was a neutral, descriptive word. Our social-studies teacher taught us that ours was a "secular" government, by which she meant that we lived free of any religion established by the state. We were to be proud of this secular government, she told us; it differentiated us from people in other times and places where those speaking for God made the rules—rules that sometimes were corrupt and unfair. As I understood it then, "secular" had nothing to do with disavowing or disapproving of any particular belief in God.

"Secular" does mean "godless," and its neutral meaning has always fought with the more negative one; recently, though, the word has taken on a lot more freight. Like the words "feminist" and "liberal," "secular" and its derivatives have come to mean extreme versions of themselves. They are code in conservative Christian circles for "atheist" or even "God hating"—they conjure, in a fresh way, all the demons Christian conservatives have been fighting for more than 30 years: liberalism, sexual permissiveness and moral lassitude. The Fox News star Bill O'Reilly frequently frames the culture war as "traditionals versus secular-progressives." Ann Coulter accused "the liberals and the secularists and atheists" of using religion as a wedge. In a speech last year, Newt Gingrich decried the "growing culture of radical secularism," and in a new book the diplomat John Bolton critiques "the High Minded elite who worship at the altar of the Secular Pope." In politics, where it is efficacious to unite people against a common enemy, "secularism" has become that enemy's new name.

To be fair, battles in the war against secularism have been fought for about 150 years, dating back to a time when discoveries in science (especially those of Charles Darwin) and a disenchantment with organized religion led a critical mass of mostly European intellectuals to declare that one could lead a moral life independent of God. By the middle of the 20th century, their heirs had coined the term "secular humanism," to mean a concern with values but not with religion, and the Rev. Jerry Falwell took particular aim at them. In 1986, he proclaimed that secular humanists "challenge every principle on which America was founded," including "abortion on demand, recognition of homosexuals, free use of pornography, legalizing of prostitution and gambling, and free use of drugs." Pope Benedict XVI speaks out frequently against the dangers of secularism.

What's new about the assault on secularism is how, among conservative pundits, it's become almost shorthand. O'Reilly doesn't have to list secularism's sins as Falwell did; he has only to utter the word. And the so-called secularists are hardly helping their own case. Aware that no group is more reviled in America than atheists, and reeling from all the attention atheists have gotten from recent best-selling books, some nonbelievers prefer to wrap themselves in a safer label: "secularist." This rhetorical deflection only makes them targets. Secularist equals nonbeliever; nonbeliever equals immoral God-hater. "It's red meat for the pundits," says Greg Epstein, Harvard's humanist chaplain. He prefers the word "humanist."

Language evolves. "Secular" was first used in the Middle Ages to mean things and people not belonging to the church—as Webster's puts it, "not overtly or specifically religious; not ecclesiastical or clerical." This remains its best and most important meaning. In this great experiment that is American democracy, "secular" is the only word we have to describe the idea, handed down by the Founders, that our leaders do not belong to God, they belong to us.