During the grimmest days of the First Crusade in 1098, the western Christians found themselves besieged by the Turks in Antioch. They had travelled more than a thousand miles from France, and countless fellow believers had died in the almost impossible trek across the known world; now running out of food and water, they were tired, hungry and desperate.

At their lowest point, and ready to give into despair, Christian spirits were raised by the arrival of one Peter Bartholomew, a poor man from Provence who claimed he had been visited by the Virgin, promising them victory. The noblemen in charge were suspicious, as Peter was not only an illiterate farmhand type but also quite shifty, yet soon momentum built around his cause. He had an audience.

Peter had then dreamed he had seen the Holy Lance, the spear which had pierced Jesus’s side on the cross, and apparently – according to his vision – was buried outside the city’s church of St Peter. So off they all went, digging for hours in the June heat to find this object and prove victory was at hand; after several hours, the exhausted Frenchmen saw Peter suddenly appear ‘clad only in a shirt and barefooted’ with a lance in his hand. He was proved correct, even if no one had actually seen him find it. Two weeks later, the crusaders won the Battle of Antioch, and the Provençal peasant’s triumph was complete.

Yet many of the those in charge were still sceptical, and the issue caused division among the crusaders, primarily along regional lines. The ‘Franks’ – as the Arabs called all crusaders – were split between the Provençals and Normans, two distinct groups whose cultural and linguistic differences dated back to the Germanic conquest of northern Gaul and beyond. The Normans didn’t believe Peter, because the Provençals did.

But the peasant was convinced of his divine support, and in order to prove it, he now announced that he would walk into a fire and emerge unhurt. The day came, the crusaders gathered, and Peter boldly stepped into the flame – and died a few days later in agony (or at least, he perished soon after, and although the exact cause of death was unconfirmed, at the very least being burned alive didn’t help).

Peter Bartholomew was displaying what evolutionary psychologists call CREDs, ‘credible displays of belief’ or ‘credibility enhancing displays’, designed to build trust and reduce hypocrisy in a community. Peter talked the talk, but he also walked the walk, literally, although his particular case was extreme and unwise; the most typical CREDs are Ramadan or Lenten fasts, but the martyrdoms of early Christians like Catherine and Blandina had a huge impact on the religion’s rise.

CREDs are one reason why religious groups almost always beat secular rivals; religious communes last on average three times as long as secular equivalents, while neighbourhoods with higher church attendance also enjoy higher levels of charitable giving and social capital, and even faith schools have an edge which others cannot quite ‘bottle’, as one former Labour education secretary put it.

Ersatz religions don’t have the same effect, and as the Nazis approached in 1941, even Stalin knew that no one was going to die for communism – the whole point of communism is that you make other people die for your beliefs – and so the churches were reopened.

People will not often make the same sacrifices for their political ideals as for their faith. Although modern progressivism clearly has many religion-like qualities, one argument against its continued dominance is that its followers aren’t willing to make CREDs, and so it will lose momentum as people begin to see it as upper-class self-interest repackaged in rainbow colours.

People are happy to pompously bloviate about diversity but they’re not going to give up their own job to make way for a woman or member of an ethnic minority. In the late 1960s, as America’s cities were consumed by violent crime, liberals fled in droves, withdrawing their sons and daughters from often-dysfunctional schools which had practised what they preached. They weren’t going to sacrifice their children’s happiness and safety for a political principle even if, they reasoned, that principle was good for the country as a whole. (Instances of conservative political hypocrisy are similarly boundless.)

Yet some people will make those sacrifices, the modern-day Peter Bartholomews of the culture wars. Just in August, five prominent talk radio personalities in the US died of Covid, having been vocal against either masks, restrictions or the vaccine itself. More recently, a well-known Italian anti-vax radio personality fell to the virus, as did a Dutch economist who thought Covid posed a minimal risk. Meanwhile in Britain, ‘John O’Looney, a funeral director and anti-vaxxer’, was due to speak at an anti-vax rally ‘but is believed to be in hospital with Covid.’

Maybe these anti-vax media personalities don’t actually believe their own shtick, and calculate that taking the Pfizer would ruin their credibility – but how likely is that? An unvaccinated man in his 50s has about a 1-in-150 chance of dying if he catches Covid, and is much more likely still to be hospitalised, put in ICU and left prematurely aged. Is a career in media really worth that?

More likely, the people with quite wacky beliefs really do believe them, just as Peter Bartholomew genuinely came to think he could walk through the fire; he wasn’t just doing it to own the Normans, or because of audience capture.

In the 1995 culture war black comedy The Last Supper, Ron Perlman plays obnoxious radio host Norman Arbuthnot, whom a group of liberal flatmates have invited over with the intention of murdering. They have already killed a climate sceptic, a Christian fundamentalist and a white nationalist, and now the shock jock is going to get it, too.

But Arbuthnot – clearly based on Rush Limbaugh – is so good at arguing with his progressive hosts that they waver in their intentions. He’s sharp, he’s intelligent, he’s sort of reasonable and, he admits, he doesn’t actually believe half of what he says, he just does it for effect, to please his audience.

I’ve heard that said a few times about Right-wing commentators; why would someone who was educated and not overtly stupid have all those obnoxious beliefs that could otherwise only stem from a lack of education?

Political debate is a status game, certainly, while hypocrisy is also universal, especially among journalists, but the chances are your opponents really do believe what they claim, and this applies even to areas that seem to defy logic. Just as the crusaders, and countless others involved in wars of religion, genuinely did believe they were carrying out God’s will, rather than, as so many historians would have it, it was all about power or some materialist explanation.

We should take people’s beliefs seriously – yet those beliefs are often arbitrary. No doubt many Norman crusaders had a good old laugh at Peter Bartholomew dying of his burns, and the southern idiots who believed him, but had the humble mystic hailed from closer to Caen than Cannes they most likely would have believed him, too.

People’s opinions tend to be tribal, and can change drastically to suit their partisan identity. New Conservative voters attracted by Brexit subsequently became more right-wing on welfare, for instance, while Republicans, formerly pro-free trade, shifted in large numbers under the influence of tribal leader Donald Trump.

In the US there is today a huge gap in vaccine uptake between white Democrats and Republicans, but could it have gone the other way? What would have happened had the vaccine been approved in October 2020, leading to a Trump victory? Although long forgotten, the politics of Covid realigned early in 2020, and vaccine politics could have gone the other way, with leading Democrats expressing scepticism about a ‘Trump vaccine’ before the election.

White Democrats tend to be more educated, but the highly-educated are also prone to irrational beliefs – they’re just better at articulating them. In Britain scepticism towards the MMR vaccine is most concentrated among highly-educated white urban neurotics, and ethnic minorities, the two core groups within the progressive voting block. Uptake is as low as two-thirds in Hackney, and not much more in Haringey, two areas with Labour super-majorities. It’s not impossible that large numbers of white Democrats would have refused the Trump vaccine.

In an alternative universe, somewhere, there are progressive media figures dying to make some idiotic point about Big Pharma, metaphorically jumping in the fire. Whether the issue is winning the Holy Land or the Covid culture wars, many people would rather be dead than be wrong.