Your title is Divided by God—and that certainly seems appropriate, given issues like abortion and gay marriage. But is it fair to say religion also unites us?

That is a fair statement. When I say "divided by God," I'm at pains to say that I don't think that it is religion itself that divides us. What divides us is that we have different ideas about how religion and government should interact. And that is a deep, divisive red state/blue state—gay marriage—Terry Schiavo—death penalty kind of problem. One reason I wrote the book is that I believe a common commitment to deeper values is something that can hold us together, and always has.

One still hears today the refrain that we are a Christian nation. Are we?

People didn't start saying we were a Christian nation until the 19th century, and what they meant then was that culturally we were a Christian nation. But even those who said we were a Christian nation never meant to say our government was explicitly a religious one. In fact, those people who said we were a Christian nation were also committed to the separation of church and state. Today, culturally speaking, we are still a majority Christian nation, but we are growing increasingly diverse.

Politically speaking, many see Bush's presidency as an ascent of religion in politics. Historically, how does the Bush presidency fit?

In the 1950s Eisenhower said that American life was based on a firm religious belief and I don't care what that is. Basically, what he meant was that we were not godless Communists. But starting with Jimmy Carter, candidates started talking more about their religious faith. This idea that President Bush says all the time, however, that religious faith can be a basis for political beliefs, I think, is a very recent trend. I think President Bush goes further than any nationally elected politician so far in speaking so openly about that.

Tell us about your background and how you approached this book.

I grew up in an Orthodox Jewish home and went to an Orthodox Jewish school and I always felt lucky because I had a foot in both camps. I had a foot in religion, and also, well, I grew up in Cambridge, Mass., so a foot in northeastern secular liberalism. I always believed there was more in common among these world views than either was prepared or able to recognize and that there was real benefit to identifying those points in common, that is to say, an aspiration to design American life in a way to be inclusive, so that as many people as possible can participate, and also a commitment to some common national vision that can make all Americans feel as if they belong.