Following the class war that marks the start of a civilisation's decline, Toynbee is delighted to tell us (Chapter 27 The nature and symptoms of social disintegration):
Yet paradoxically this explosive process of disintegration ends in positive achievements — the creation of a universal state, a universal church, and barbarian war-bands [Terrorists].
In creating barbarian war-bands [Terrorists] the external proletariat has merely prepared itself for a destructive attack upon the dying civilization.
It should be noted that the 'universal state' is the general chaos won by the collapse of ordered societies following the widespread decay of understanding. And this mass confusion inevitably embraces a common hysteria that becomes the 'universal church'.