Political extremism involves two prime ingredients: an excessively simple diagnosis of the world's ills, and a conviction that there are identifiable villains back of it all.
Like fundamentalist Judaism and medieval Christianity, Islam is totalist. That is to say, it makes a total claim on the individual.
Since the day of the air, the old frontiers are gone. When you think of the defense of England you no longer think of the chalk cliffs of Dover; you think of the Rhine.