Few movements have been as single-minded in their commitment to modernization as Lenin’s Bolsheviks, and few have been so virulently hostile to mainstream faiths. Yet as Bertrand Russell observed in his forgotten 1920 classic The Practice and Theory of Bolshevism, written after he travelled to Russia and talked with Lenin, Soviet communism was from the beginning as much a religion as a political project. Oddly, though it was a rerun on a vaster scale of the French revolutionary terror that she analyzes so penetratingly, Armstrong says practically nothing about the Soviet experience, or about Maoism. Yet, together with Nazism, these 20th-century state cults plant a question mark over the very idea of secularization. Certainly there has been a decline in the old authority of churches, but that does not mean religion is becoming weaker. Simultaneous with the retreat of the mainstream faiths, there has been a rise of a plethora of political religions and an explosion of fundamentalism, sometimes fused in a single movement.

The ambiguities of secularization are especially prominent in the Middle East. What does Islamic State stand for—an ultra-violent type of religious fundamentalism, or a radically modern politics? Clearly, it represents both. Armstrong provides some of the background to the emergence of IS when she discusses Wahhabism, the 18th-century Islamic movement whose founder, Ibn Abd al-Wahhab, helped establish the first Saudi state. Since the influx of oil wealth, the Saudis have promoted Wahhabism worldwide. IS is one of the offspring of this project: an ogre that is now a deadly threat to the Saudi state. A potential for violence was present in Wahhabism from the start. But Armstrong tells us that it “was not inherently violent; indeed, Ibn Abd al-Wahhab had refused to sanction the wars of his patron, Ibn Saud, because he was simply fighting for wealth and glory.” As an argument for the peaceful character of the movement, this is less than compelling. The clear implication of the founder’s statement is that war would have been justified if it had been waged in the service of faith.