Al Qaeda asks its recruits to establish their bona fides as a condition of membership, even requiring answers to a long questionnaire. But ISIS has democratized and globalized jihad by lowering the entry bar to an eve-of-destruction YouTube pledge of allegiance to the caliphate - and even that could probably be waived.

Liberal democracies like ours seem, for the most part, to have learned how to avoid meticulously planned mass-casualty plots with the complexity and scale of 9/11. But they don't know how to keep their citizens safe at night clubs and concerts, in supermarkets, on beachfront promenades, from truck drivers.

Certain murderous ideas are in the air worldwide, and they are finding individuals in scattered places in different ways, and every attack spreads them further, plants an idea in a new head.

George Packer Quotes