Ever since 9/11, it has been a central tenet of America's national security establishment that the threat of jihadist terrorism and the proper way of contending with that danger have nothing to do with Islam - except to the extent al Qaeda (or, more recently, the Islamic State) "perverts" or "hijacks" that religion. But what if this characterization of the problem we continue to face fifteen years on is simply and utterly wrong? What if there...