That most Christian theologians have adapted to secularisation in a way that most Islamic ones have not is obviously true; but Pagden is saying more than that. His claim is that there has been a more or less permanent difference between the two worlds. In the world of Christianity, law has been seen as merely human, and the Church has not claimed “social or political authority as such”; in the world of Islam, the very idea of a man-made secular law, not derived directly from Sharia law, has been regarded as almost “senseless”.

This is a huge over-simplification. The Christian Churches have claimed many varieties of social and political authority — whether the “indirect power” of the Pope over Christian kings, as defended by Jesuit theorists, or the direct control of moral life, as exercised in Calvin’s Geneva (and in ecclesiastical courts, Europe-wide). For many centuries, Christians believed that law was founded on morality, and that morality was founded on religion; many Christians still do.

As for Muslims finding the idea of a secular law unthinkable: Pagden ignores here the legal system of one of the greatest Muslim states of all time, the Ottoman Empire, which was never simply dependent on sharia law. The Sultan’s kanun or law-code included also his own (man-made) decrees, and elements of what was known as adat, the customary laws of his various peoples. To airbrush such details out of the picture is to create an unhistorical account, in which the rise of radical Islamism, instead of being a historical development that needs to be explained, is made to seem like an expression of an Islam that is timeless and unchanging.