Dietrich Bonhoeffer knew more than you or I are likely to ever know about about the line between stupidity and outright evil. The Lutheran pastor and theologian had a front row seat as he watched the Nazis—history’s evilest stupid people (or stupidest evil people )— ascend to power and come to rule through terror during the 1930s and ‘ 40s. I n a letter to his friends, family, and followers written w hile he awaited execution at Flossenbürg concentration camp for his role in the July 20, 1944 assassination attempt on Adolph Hitler, Bonhoeffer detailed his thoughts on the root...