IT IS a puzzle for anyone who thinks about history that theological quarrels are so clearly absurd. I am awed by the courage of martyrs at the stake: the story of Cranmer returning his hand to the flames has stayed with me since I was first shown the Martyrs’ Memorial when I was seven. It is the asymptote of courage and conviction.

Yet, what was all that courage and conviction for? No one would now kill or die for the belief that the papacy was the Antichrist. The Anglican-Roman Catholic International Commission seems to have concluded that the Reformation was based on a mutual misunderstanding, that’s all. It is impossible for us to enter into the 17th-century understanding of these disputes as worth killing or dying for.

Papal supremacy is another matter. As a political cause, it makes complete sense to declare that England is an empire, in which the Church is governed by the (Christian) King and not the Pope of Rome. But that’s the sort of question on which compromise is possible: look at the Vatican’s dealings with China today, or with the Soviet Empire before that. Whether the mass is a blasphemous fable is a different sort of question altogether: one that must have a correct and unambiguous answer, but where there is no possibility of an appeal to empirical evidence. You might think that the sane thing is just to agree to disagree, but there are times when that seems quite impossible.

Which times? Those when the old order is breaking up and the new one has not formed. That is when you need to divide the sheep from the goats, and to make sure that the goats are utterly crushed (the Psalms are eloquent on the proper fate of the unrighteous), and this is what absurd and empirically unanswerable questions are useful for. They become pure tests of conviction and political strength. The content of the ideology does not matter: what matters is that it should work as a shibboleth.

The historian and social scientist Peter Turchin has a theory of the causes of social breakdown which is fascinating, convincing, and cheerless for people living through the collapse of the American Empire. One aspect of it is that he doesn’t believe that the content of ideologies matter: what matters is their target and their political effect.

I thought of these questions when considering the rather different cases of Charlie Kirk and Danny Kruger. The consensus of political writers on Mr Kruger, an MP who defected from the Conservatives to Reform UK this week, is that he’s nice but nuts. Kirk seems to have been less nice and much more successful as a politician.

But, in both cases, the defining quality of their ideological fervour is that you know who their enemies are, not which principles they might stand for. Mr Kruger, who two months ago delivered a passionate speech against assisted dying and late-term abortion to an almost empty House of Commons (News, 25 July), has now joined a party that favours the assisted-dying Bill. Kirk’s conservatism required the destruction of all the institutions that had made the United States strong and admired throughout the world. In both cases, the principles are adjusted, like sails, to catch the winds of popular hatred and drive the project on.

But the project has some goal. Presumably, Mr Kruger believes that, when liberalism collapses, something better and more Christian will take its place. Much of the violence now emerging in the US is wholly nihilistic. All that the murderers want is fame and destruction.

Kirk’s assassin followed a fashion in recent American mass murders for engraving slogans and in-jokes on the cases of the cartridges that he used. According to Charlie Warzel in The Atlantic, “the fired bullet casing found on the scene had been inscribed with the phrase ‘Notices bulges OwO what’s this?’ — a niche online reference to flirting within the furry community that is now mostly just used trollishly.’”

Another bullet casing was engraved with the trollish phrase “If you read this, you are gay lmao.” As Warzel wrote about the previous horror — the murder of Roman Catholic children in a church by a young man who turned the gun on himself (News, 29 August) — “This is irony-poisoned nihilism, tactical gear as shitposting — the only cause this person seems to have is to troll the viewer.”

When people used theology to justify the slaughter of their enemies, the words that they used meant something, or pointed, as they believed, to some truth. From our perspective, this all seems absurd. But the armed nihilist murderers of the US have skipped the stage of meaning altogether and moved straight into absurdity. It’s a fresh glimpse of hell. I should go back and read some Dostoevsky.