I’m swimming in very deep waters here, Jonah, but I’m not sure that it’s possible to draw that bright line between the murderous ’secular’ philosophies of the twentieth century and what went before. Looking, for example, at the fury and bloodshed of some of Europe’s nastier religious wars, isn’t it possible to think that the reason that the protagonists did not indulge in twentieth century style slaughter was that they did not have the technology?

Better I think, to look beneath the very different beliefs professed by the mass murderers, and see what unites them. Some will be cynics merely using an ideology for their purposes, while others, more dangerous, are the true believers – in the ‘People’ perhaps, or a god – who feel that so long as they are acting in the interests (as they interpret it) of their faith any atrocity can be justified, however appalling.

Yes, belief in a god can often act as a welcome restraint on the worst of human nature because of the threat (or the promise) it brings with it – that every individual will one day have to account for his actions to a higher authority – but it’s no guarantee.