The problem faced by the orthodox religious authorities in the Muslim world, however, is very similar to that which confronted the Catholic Church in the 16th century: escaped genies are tricky things to get back into bottles. The same impulse that prompted Luther to affirm the primacy of scripture over Catholic doctrine has also long been at work in Islam. As far back as the 13th century, a scholar based in Damascus by the name of Ibn Taymiyya proposed that the surest way to know God’s purpose was to study the practices of the first three generations of Muslims: the “forebears”, or “Salafs”. Reports of what Muhammad and his earliest followers had done, so he argued, should always trump subsequent tradition. Like Luther, Ibn Taymiyya was condemned as a heretic; but he also, again like Luther, blazed a momentous trail.
Salafism today is probably the fastest-growing Islamic movement in the world. The interpretation that Isis applies to Muslim scripture may be exceptional for its savagery – but not for its literalism. Islamic State, in its conceit that it has trampled down the weeds and briars of tradition and penetrated to the truth of God’s dictates, is recognisably Salafist. When Islamic State fighters smash the statues of pagan gods, they are following the example of the Prophet; when they proclaim themselves the shock troops of a would-be global empire, they are following the example of the warriors of the original caliphate; when they execute enemy combatants, and impose discriminatory taxes on Christians, and take the women of defeated opponents as slaves, they are doing nothing that the first Muslims did not glory in.