Quick: Name the four Gospels. How about the Ten Commandments? The Four Noble Truths of Buddhism? Seven Catholic sacraments? Hello? Anybody?

America purports to be a religious nation, yet what we know about religion is, well, sinful. In his new book, "Religious Literacy: What Every American Needs to Know -- And Doesn't," Stephen Prothero, head of Boston University's religion department, says it's time to teach religion in America -- not devotion, but religion.

Prothero and others have found a shocking lack of knowledge about the religions to which Americans purport to belong, bested only by their ignorance of religions to which they don't belong. Surveys say only half of America's adults can name any of the four Gospels. Most Americans can't name the first book of the Bible. Only one-third know that Jesus (not Billy Graham) delivered the Sermon on the Mount, and most Americans think Jesus was born in Jerusalem. (It was Bethlehem.) Yet, Prothero writes, "World events have been shaped by Confucian ritual, Jewish law, Christian love and Buddhist compassion."

In this country, Christianity, in particular, has migrated from doctrinal and narrative components to a focus on religious experience that doesn't appear to require a knowledge of the Scriptures, Prothero says.

"Being a Christian has become synonymous with having a born-again experience or opposing abortion and stem-cell research," he says. "American Christians focus on loving Jesus rather than learning what He taught."

In his research, Prothero says he was surprised to learn that the U.S. government pays little attention to religion when forming foreign policy. That observation got a big laugh March 19, when Prothero appeared on "The Daily Show With Jon Stewart."

For example, Prothero says, "U.S. ambassadors to Muslim-majority countries are typically political cronies who have no training in Islam. And there is no policy of having our ambassador to India, say, know something about Hinduism. This is a scandal."

The problem is not hypocrisy, Prothero says, so much as ignorance.

"When I give my students the religious-literacy quiz that's in my book, I find Catholics who don't know the seven sacraments, Protestants who can't name any of the four Gospels and Jews who can't name the first book of their Bible. That doesn't make them pseudo- religious. It just makes them believers who don't really know what they are believing in," he says.

He suggests religion be added as the fourth "R" in American education. (A recent Time magazine echoes his suggestion for teaching the Bible, the historical best-selling book ever, in schools.) After all, Prothero says, the Constitution doesn't prohibit teaching about religion. It bans teaching a particular religion.

"I think there (is) now a fairly high level of public resolve to do something about our ignorance," he says. "Moreover, the momentum is building. Most Americans are in the middle when it comes to the so-called culture wars. We hear about the wacky folks on the secular left (who fear almost any discussion of religion in the schools) and on the religious right (who want their religion to be the only religion taught in the schools).

"But the vast majority of us are in between, and that is where the hope lies."