When Martin Luther wrote his Ninety-Five Theses in 1517, he didn’t just publish a scathing critique of the Catholic Church—he launched a theological and liturgical revolution that would impact the entire world for centuries to come. In her meticulously researched new book, Martin Luther: Renegade and Prophet (Random House, March), Oxford historian Lyndal Roper explores the man behind the Reformation, delving deep into his inner life and providing a rich understanding of the world in which he lived.

What sets your book apart from other biographies of Luther?

Most biographies of Luther have been written by church historians, but the questions that interest me are those that a social and cultural historian would ask, not necessarily the questions that a theologian would consider important. I look at Luther psychologically and in his historical context. I’m interested in how he experienced things, how he felt about things, and how his views changed over time—tracing the unfolding of a life from childhood through death.

What was your research process like?

It was very important to me to have a sense of place and go everywhere that Luther had been. I went to Mansfeld [in Germany], the old mining town where Luther spent most of his childhood. I also spent time in Wittenberg where he spent much of his adult life. I especially wanted to understand how the economies of these places worked and how Wittenberg changed as the university grew in the wake of Luther and the Reformation. I also wanted to get as close to him as I could, so I read a little bit of Luther every day. The experience of that encounter with Luther was one of the things I have most enjoyed as a scholar.

What surprised you most about Luther as you were working on the book?

How extreme his anti-Semitism was. I wasn’t expecting that and certainly wasn’t expecting it to be quite as physical as it was. For example, shortly before he died Luther declared that his next major task would be expelling the Jews from Germany and even feared he had become sick because the Jews had “breathed” on him during his travels. The other thing that surprised me was how much energy he spent focusing on the physical presence of Christ in the Eucharist.

What do you admire most about Luther?

His courage. His ability to stand up to the Emperor in 1521 at the Diet of Worms [the imperial assembly of the Holy Roman Empire] is absolutely amazing. The path he takes is extraordinary because he’s not courting martyrdom. In fact, he’s very careful to set up a series of things that will protect him from burning. But, even knowing how dangerous it is, he never turns away from the conflict with the pope.

Luther eventually married a nun and, according to your book, had a fairly healthy attitude toward sexuality. Can you tell me more about Luther’s views on sex and gender?

I found his attitude toward the body and sexuality really wonderful. When many former monks and priests married, they maintained much of their asceticism and aversion to sexuality — especially female sexuality and the female body. But Luther believed that God had instilled sexual desire in both men and women and that it was human nature. I was particularly struck by a moment before his wedding where he writes that it might be a “Joseph marriage,” meaning a chaste marriage. That was before he’d ever slept with a woman and it’s interesting that he has a sort of transformation and does decide to have sex and children with his wife.

What do you think Luther would think about the modern Lutheran church?

There’s a point in 1539 when his works are first collectively published, and he writes in the preface that he hopes his books won’t survive and people will read the Bible instead. So I think if you asked him today he would say we should just be reading the Bible and forget all this rubbish about Luther. On the other hand, however, I don’t think he was being entirely honest. He was a very big personality and he might not even be surprised that so much is still being made of him.