Jim Wallis is one of America's most prominent progressive Christians. But as a teenager, he wanted to leave the church for good.

Wallis grew up in Detroit in the 1950s and 1960s, gradually becoming aware of the city's complicated racial politics. His white church didn't acknowledge the struggles of the city's black residents, and he wanted to know why.

"An elder in my home church took me aside and said, 'Son, you have to understand. Christianity has nothing to do with racism. That's political and our faith is personal,'" Wallis recalled during his keynote address at the American Academy of Religion's annual conference on Nov. 18.

Wallis wasn't satisfied with that answer, so he separated from his childhood faith. As a young adult, he fought for causes in secular ways, protesting against racism, poverty and war.

Gradually, this activism drew Wallis back to Christianity, which he said nourishes and strengthens his social justice work. It also helped him find what he'd been searching for since that conversation with the church elder.

"I didn't have words for that elder back then, but I do now. God is personal, but never private," he told the crowd of theologians, religious studies scholars and writers gathered at the conference in Denver. God should inspire Christians to build a better world.