From The Economist.

I guess most people in the UK have forgotten the IRA campaign in the 1970s and 1980s. Or the Lockerbie bombing in 1988. The difference between then and now (apart from the numbers killed and injured) is that the IRA had a set of ‘political’ objectives, and in the end it was possible to negotiate with them — which is how the Good Friday Agreement came about. But Islamic terrorism doesn’t have any negotiable objectives — unless you count the extermination of ‘infidels’ as one.