Historian Diarmaid MacCulloch, the prize-winning Oxford emeritus professor behind several books and popular BBC series, suspects his often-surprising new book, Lower than the Angels: A History of Sex and Christianity (Viking, April) might set some traditionalist critics' hair on fire. In his look at three millennia of religious history he asserts there's no such thing as "traditional marriage," is supportive of LGBTQ relationships, and more.

PW talks with MacCulloch about his book's conclusion that "The Bible has not proved adequate to providing answers on questions of sex and gender."

There are many burning topics in the Bible that a historian could tackle. Why did you zero in on sex for this encyclopedic book?

I did because there are things said about sex in the Christian tradition and things misunderstood from the Hebrew Scripture and the Christian New Testament that are still affecting people's lives, their emotional lives, and their identities, and that are actually the fruit of ignorance and wishful thinking. What I've tried to do is to cut through all that and present the reality of the past.

For example?

One of the extraordinary present debates is about equal marriage, whether same-sex marriage is equal to heterosexual marriage and both kinds of couples can be married in church. I lay in front of readers the basic fact until the fifth century, no one went to church to get married. No one at all. Then, only elite people had a church ceremony. But in the Western church, the Catholic church that is the ancestor of Protestantism, no one went to church to get married until virtually the 12th century. That's more than half of Christian history.

You write that the 1690s were a turning point in Western social and religious history. What happened?

It was the birth of choice, the privatization of individual discernment. In the late 17th century, England and the Netherlands banished hunger for the first time in human history because their agriculture was so efficient. That means your life has changed because you're no longer thinking about how to survive. You begin to build up spare cash, and you can make little choices, even if you're very poor. You could think about choosing who you were, not just being a peasant on someone else's land, having your identity given to you. Once people began choosing, they could choose what it meant to be a man or a woman. They could choose their emotional life.

You make a case that while Jesus is the word of God, the Bible as a whole is not. Won't that surprise -- and anger -- some people?

Does the Bible describe itself as the word of God? No. There's only one passage where you might read that, it's in 1 Timothy, which is probably a forgery. Listening to a forgery talking about the inspired Word of God doesn't seem to me to be a very good principle. And if you start from a mistaken principle, you feel really threatened when someone points out it it's not true, that the whole worldview that you've built on it is just too fragile to stand. A lot of conservative Christian theology is that fragile. They're terrified of it falling over and collapsing, so they've got to stop any attempt to revise it.

You conclude in the book, "We have yet to realize and discern all of Christianity's potential riches." Where is Christianity heading?

Historians are very bad prophets. We tell you what happened in the past, and we're trying to get that right, but we are hopeless in trying to predict what comes next.

Who is the audience you have in mind for this book?

It is designed for the thoughtful general public, which, praise be, still exists. Very often this thoughtful clientele gets disheartened because it's overwhelmed by the noise of simple arguments. They're relieved to find things are actually much more complex than the narratives that are being thrust at them.