In the preface to Martin Luther, the latest of his more than 50 books, theologian Martin Marty defines his role as biographer as neither “a hanging judge or a flack.” But he admits that his portrait of the 16th-century German priest may not find favor with all of the flock.

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“There are a lot of Lutherans who would like a portrait of Luther in which he is not so agonized, so doubting,” says Marty, an ordained Lutheran minister and professor emeritus at the University of Chicago. “When he doubts, he really, really doubts. Doubt for him is just not a little intellectual weakness. Doubt is not something the devil does to you. No, this kind of doubt is way bone deep and it must belong to the will of God. To me–my Luther always wrestles, always struggles: ‘God, you’re bigger than I am. You’re more mysterious. I’ll never get anywhere.’ And yet, God descends enough into our world that in this wrestling match we get to win. Win against meaninglessness, doubt, despair, depression. I think part of his genius is he just went deeper on what all of us do all the time.”

Marty first made a name for himself as a young Concordia Seminary student in Saint Louis when he and a classmate invented a fictional thinker, Franz Bibfeldt, who soon took on a life of his own. Marty and his friends cited Bibfeldt in their papers and in his senior year Marty published a review of Bibfeldt’s treatise “The Relieved Paradox” in an issue of the Concordia Seminarian. School authorities were not amused. “Is this a satire on one of us, or all of us?” asked the president. A covert fan of the stunt, he was consoled to hear it was nothing personal, but Marty’s postgraduate assignment in London was canceled. “They said, ‘You’re too immature and irresponsible to represent the church in England and you need seasoning,’” remembers Marty with a laugh. “So they sent me to assist in River Forest.”