IS bases its terrorism on a vicious calculation. It believes that successful attacks will inspire the would-be Muslim radicals that it is trying to recruit. But it also wants to provoke a backlash in order to convince those same radicals that the world despises them and their religion. In February IS propaganda described a “greyzone” in which some Muslims’ loyalty is divided between radical Islam and a country where they do not feel that they completely belong. IS wants terrorism to drive Muslims out of this greyzone and into the black-robed embrace of the Caliphate.
The response must be just as calculating. Leading the mourning this week, François Hollande, France’s president, vowed to destroy IS. That is a worthy aim, but a partial one, because other jihadist groups with equally murderous intent will thrive in the violent crevices of the Middle East. The struggle will be long. Countries therefore need policies that they can sustain even as the Middle East remains turbulent and, inevitably, the terrorists sometimes get through.
Remember that the West has two things to defend: the lives of its citizens, and the liberal values of tolerance and the rule of law that underpin its society. Where these are in conflict, it should choose policies that minimise the damage to values in order to make large gains in protection. Sadly, in the scramble for security, that principle often seems to be the first thing to go.
The starting-point for a safer world is at home, with the right legal powers. Jihadists are often radicalised online, in small groups. They communicate electronically. When they travel, they leave a trail. The intelligence services need controlled access to these data. Terrorists thrive on secrecy, yet the security services may abuse their powers. The solution is a legal framework subject to political and judicial scrutiny.