Whether by choice or not, the West finds itself in a low-grade yet bitter war with Islamic fanaticism. It is a war the West is singularly ill-equipped to fight. The foe is resistant to any of the normal methods of conflict resolution such as negotiation, economic sanctions, or conventional armed confrontation. Since the Enlightenment, the West has forgotten how to oppose fanaticism, and it is Lee Harris's goal to remind us what we are up against.

In The Suicide of Reason, he explains the logic of fanatical movements from the Crusades through Nazism to radical Islam; describes how the...