I was surprised last week to learn how easily some Westerners believe terrorism can be explained. The realization unfolded as I looked into the sad face of a student at Oxford University. After giving a speech about Islam, I met this young magazine editor to talk about Islam's lost tradition of critical thinking and reasoned debate. But we never got to that topic. Instead, we got stuck on the July 7 bombings in London and what might have compelled four young, British-raised, observant Muslim men to blow themselves up while taking innocent others with them. She emphasized their "relative economic...