Journalist Susan Jacoby, author of a dozen books including the bestseller The Age of American Unreason (Pantheon, 2008), is coming out with a new book following 15 years of research. Strange Gods: A Secular History of Conversion (Pantheon, Feb.) looks at religious conversion across hundreds of years of history to uncover some of the often secular reasons for why people convert.

Strange Gods focuses on religious conversions that take place apart from purely spiritual reasons. What are some of the other factors that often contribute to a person’s religious conversion?

People generally think about conversion only in terms of a spiritual journey, when in fact, there are a lot of secular factors involved. Sometimes it is simply that the political winds have shifted. Another factor is discrimination against minorities. That was a huge factor in my father’s family because of anti-Semitism— people perceived being a Jew as a disadvantage. Also, the history of conversion is rife with people who adopt religion or another religion because they think it will help them overcome a personal failing or some compulsion like alcoholism, and in many cases, it does. But the most powerful secular factor promoting religious conversion is religious inter-marriage.

What surprised you the most while writing Strange Gods?

What I found most surprising was how different American attitudes are concerning religious conversion compared to the rest of the world. America was founded not as a Christian nation, but rather on the idea that whatever religion you choose is none of the government’s business. American attitudes about conversion are so much more the normative experience than it is in the rest of the developed world. In places like France, it is so much more unusual to convert to another religion—they become secularists if they don’t believe the religion they were born into. But here in America, the idea is that you choose some religion.

How do you think the motivations of people converting from one religion differ from the motivations of people leaving religion altogether?

With few exceptions, people leaving religion aren’t converted to atheism. Conversion is when you believe one thing one day and believe some other ideology the next. For me, I went to Catholic school and it never made sense to me. But it is not as if the light finally dawned on me, which is something you hear in many conversion stories. For most secularists, it tends to be a gradual sliding out of religious belief.