They called Abraham Bredius “The Pope”, a nickname that poked fun at his self-importance while acknowledging his authority. Bredius was the world’s leading scholar of Dutch painters and, particularly, of the mysterious Dutch master Johannes Vermeer.

When Bredius was younger, he’d made his name by spotting works wrongly attributed to Vermeer. Now, at the age of 82, he had just published a highly respected book and was enjoying a retirement swan song in Monaco.

It was at this moment in Bredius’s life, in 1937, that Gerard Boon paid a visit to his villa. Boon, a former Dutch MP, was an outspoken anti-fascist. He came to Bredius on behalf of dissidents in Mussolini’s Italy. They needed to raise money to fund their escape to the US, said Boon. And they had something which might be of value.

Boon unpacked the crate he had brought out of Italy. Inside it was a large canvas, still on its 17th-century wooden stretcher. The picture depicted Christ at Emmaus, when he appeared to some of his disciples after his resurrection, and in the top left-hand corner was the magical signature: IV Meer.

Johannes Vermeer himself! Was it genuine? Only Bredius had the expertise to judge.

The old man was spellbound. He delivered his verdict: “Christ at Emmaus” was not only a Vermeer, it was the Dutch master’s finest work. He penned an article for The Burlington Magazine for Connoisseurs announcing the discovery: “We have here — I am inclined to say — the masterpiece of Johannes Vermeer of Delft. Quite different from all his other paintings and yet every inch a Vermeer.”

He added, “When this masterpiece was shown to me, I had difficulty controlling my emotions.”

That was precisely the problem.

“Christ at Emmaus” was a rotten fraud, of course. But although the trickery was crude, Bredius wasn’t the only one to be fooled. Boon had been lied to as well: he was the unwitting accomplice of a master forger. Soon enough, the entire Dutch art world was sucked into the con. “Christ at Emmaus” sold to the Boijmans Museum in Rotterdam, which was desperate to establish itself on the world stage. Bredius urged the museum on and even contributed. The total cost was 520,000 guilders — compared to the wages of the time, well over $10m today.

“Emmaus” drew admiring crowds and rave reviews. Several other paintings in a similar style soon emerged. Once the first forgery had been accepted, it was easier to pass off these other fakes. They didn’t fool everyone but, like “Emmaus”, they fooled the people who mattered. Critics certified the forgeries; museums exhibited them; collectors paid vast sums for them — a total of more than $100m in today’s money. In financial terms alone, this was a monumental fraud.

It is also a puzzle. Vermeer is revered as one of the greatest painters who ever lived. He painted mostly in the 1660s, and no more than 40 of his paintings were thought to have survived. The discovery of half a dozen new Vermeers in just a few years should have strained credulity. But it did not. Why?

The paintings themselves provide no answer. If you compare a genuine Vermeer with the first forgery, it is hard to understand how anyone was fooled, let alone anyone as discerning as Bredius.

Even to the most casual art lover, Vermeer stands out as a master. Consider his “Woman Reading a Letter”. She stands in the soft light of an unseen window. Is she pregnant? She holds the letter close to her chest, eyes cast down as she reads. There’s a dramatic stillness about the image — we feel that she’s holding her breath as she scans the letter for news.

“Christ at Emmaus” is a drab, static image by comparison. The yellow-sleeved arm of a disciple seems more attached to a table than to his body, like a prank prosthetic. Christ’s eyelids are droopy and strange — distinctive markers of the forger’s style. And yet this picture fooled the world.

Why were people so gullible? And, as we gaze back through time at an entire community falling for an obvious con, is there a lesson we should learn today?

Those questions are why I find the “Emmaus” forgery so fascinating. In recent years, I have seen people believe that Donald Trump is the perfect person to clean up corruption in politics; that the British government “holds all the cards” in Brexit negotiations with the EU; that Covid-19 is no worse than flu and that if we only lifted lockdowns it would fade away. There are certain things that large numbers of people believe, despite the most straightforward evidence to the contrary. I wanted to understand why we work so hard to fool ourselves.

In 2011, Guy Mayraz, then a behavioural economist at the University of Oxford, conducted a test of wishful thinking. Mayraz showed his experimental subjects a graph of the price of wheat rising and falling over time. He asked each person to make a forecast of where the price would move next and offered them a small cash reward if their forecasts came true.

Mayraz had divided his experimental participants into two categories. Half of them were told that they were “farmers”, who would be paid extra if wheat prices were high. The rest were “bakers”, who would earn a bonus if wheat was cheap.

The subjects could earn two separate payments, then: the first for making an accurate forecast; the second, a random windfall if the price of wheat happened to move in their direction. Yet Mayraz found that people tended to forecast what they hoped would happen. The farmers hoped that the price of wheat would rise and they also predicted that the price of wheat would rise. The bakers both hoped and predicted the opposite. This is wishful thinking in its purest form: letting our reasoning be swayed by our dreams.

It’s one of many studies demonstrating what psychologists call “motivated reasoning”. Motivated reasoning is thinking through a topic with the aim of reaching a particular conclusion. Sometimes it’s a conscious process, as with a lawyer in the courtroom or a candidate in a political debate. Often it is as instinctive as the sports fan’s limitless capacity to blame the bias of the referee.

I could see wishful thinking in operation over and over again during the pandemic of 2020. To pick just one example, there was a moment in the summer when people started to realise that sometimes tests for Covid-19 had a false positive rate: they would flag the disease even when it wasn’t there. From that dangerous little piece of knowledge came a comforting theory: as the first wave passed in Europe, perhaps the virus was gone completely. A few commentators loudly declared that there would never be a second wave. When infections ticked up again, they claimed these were just false positives.

This story never really made much sense. False positives exist but why would they increase? And then hospitalisations rose too. Then deaths. A few people kept shouting about false positives. The rest of us could see the sad truth. It seems tragic and ridiculous with hindsight. But let’s not feel too smug.

If the truth is painful enough, we are all capable of clutching at comforting falsehoods. Political diehards find ways to ignore the painful experience of electoral defeat, from Jeremy Corbyn’s much-mocked claim after badly losing the 2019 general election in the UK that on many issues “we have won the arguments”, to Donald Trump’s far more malevolent assertion that the US presidential election was rigged. Tens of millions agree.

Wishful thinking isn’t the only form of motivated reasoning, but it is a common one. A “farmer” wants to be accurate in his forecast of wheat prices but he also wants to make money, so his forecasts are swayed by his avarice. A political activist wants the politicians she supports to be smart and witty and incorruptible. She’ll ignore or dismiss evidence to the contrary.

And an art critic who loves Vermeer is motivated to conclude that the painting in front of him is not a forgery but a masterpiece. It wasn’t “Christ at Emmaus” that fooled the world. It was wishful thinking. And we might continue to be fooled to this day had the forger not been caught out by a combination of recklessness and bad luck.

The unravelling began with a knock on the door. It was the evening of May 29 1945. The war in Europe was at an end.

The reckoning was just beginning. The door belonged to 321 Keizersgracht, one of Amsterdam’s most exclusive addresses. Outside stood two soldiers from the Allied Art Commission. The door swung open to reveal an artist and art dealer named Han van Meegeren. The Dutch had just endured the near starvation of what they called the “hunger winter” but the visiting soldiers could see that at 321 Keizersgracht there was plenty of everything.

And Van Meegeren owned more than 50 other properties scattered across the city. At 738 Keizersgracht, a 15-minute stroll away, he hosted regular orgies at which prostitutes, driven into his orbit, were offered the chance to grab a fistful of jewels in the hallway as they left. Where had the money come from for all this?

The soldiers thought they knew. A masterpiece by Johannes Vermeer, “The Woman Taken in Adultery”, had been found in the possession of a German Nazi. And not just any Nazi but Hermann Goering, Hitler’s right-hand man. The paper trail led back to Van Meegeren, as did several other transactions involving other Vermeer paintings. Where had he obtained these Dutch treasures?

Van Meegeren was in serious trouble: treason could carry the death penalty. He was arrested and marched at gunpoint across town to prison. After days of furious denials, he cracked.

“Idiots! You think I sold a Vermeer to that fat Goering? But it’s not a Vermeer. I painted it myself.”

He claimed the others, too — including “Christ at Emmaus”. The confession seemed absurd, a wild attempt to escape the firing squad. How did Van Meegeren propose to prove it?

I was just a boy when I first read about this tale. I was charmed by the idea that the despicable Goering had been duped by a master forger. I relished the irony of the situation Van Meegeren found himself in: to escape execution, he needed to prove that he’d committed a different crime.

I am not the only one to have been fascinated. Many biographies have been written about Van Meegeren — including authoritative accounts by Edward Dolnick and by Jonathan Lopez, on which I have relied in retelling the story. There is even a recent movie, The Last Vermeer. Van Meegeren is box office.

But the more I studied the story, the more I found my gaze drawn instead to Abraham Bredius, the art critic who first fell for the fraud. Van Meegeren is fascinating because he seems unique. But Bredius is compelling for the opposite reason: his mistake is all too typical.

Bredius’s stumble is much more than a footnote in the history of art. It can teach us why we buy things we don’t need or become infatuated with the wrong kind of romantic partner. It explains why we vote for politicians who betray our trust, fall for implausible theories about the coronavirus and repeat statistical claims that even a moment’s thought would tell us cannot be true.

I recently published a book about how to use numbers to think clearly about the world and had pondered what sort of technical advice I should dispense first. Then I realised I shouldn’t be offering technical advice at all. Instead, I began with the case of Abraham Bredius. Bredius knew more about his chosen subject than most of us will ever know about anything — and yet he was fooled.

Recall that Bredius wrote, “I had difficulty controlling my emotions.” That was a truer statement than he knew. When we are trying to interpret the world around us, we need to realise that our expertise can be drowned by our feelings.

Wishful thinking enabled Bredius’s seduction, but there was more to his error than the mere hope of finding one more Vermeer. He had published a number of conjectures about a mysterious gap in Vermeer’s painting career. Might Vermeer have been working on biblical paintings, perhaps? Bredius fondly speculated about a link with the Italian master Caravaggio. Van Meegeren was a forger who understood his victim all too well. He created “Emmaus” to confirm all Bredius’s theories. It was on the same theme, and even echoed the same composition, as a tense and understated “Emmaus” by Caravaggio himself. When Bredius saw the picture, he didn’t just see a painting. He saw proof that he had been right all along.

The French satirist Molière once wrote that “a learned fool is more foolish than an ignorant one”. Modern social science suggests that Molière was right. In 2006, the political scientists Charles Taber and Milton Lodge looked at motivated reasoning about gun control and affirmative action. They asked people to evaluate various arguments for and against each position — and they found, as you might expect, that their subjects’ political beliefs interfered with their ability to dissect the strengths and weaknesses of the arguments in front of them.

More surprising was that the process of reading the arguments pushed people further towards political extremes. This was because they grabbed on to arguments they liked and quickly dismissed the rest. Even more striking was that this polarising effect was stronger for people who already knew a lot about civics and politics. These well-informed people were better at cherry-picking the information they wanted. More information and more expertise produced more strongly motivated reasoning.

This effect is most apparent in views on climate change in the US: not only is there a huge gap between Democratic and Republican supporters over how concerned they are about climate change but the gap grows wider among Republicans and Democrats with higher levels of education and scientific literacy. Greater knowledge does not guarantee convergence on the truth; when coupled with motivated reasoning it can simply provide fuel for polarisation.

From his Monaco villa in 1937, Bredius offers us the perfect warning about the dangerous combination of wishful thinking and deep expertise. Bredius noticed details about the forgery that a less skilled observer would have missed. Those details led him astray.

The bright speckles on the bread seem a bit clumsy to the untrained eye but they reminded Bredius of the highlights on a tempting loaf of bread in Vermeer’s “The Milkmaid”. Bredius noted that “Emmaus” depicted a 17th-century water jug in a biblical scene, an anachronism that spoke of authenticity. Van Meegeren, of course, was one step ahead. He had obtained a 17th-century antique and used it as a prop.

Van Meegeren had bought years’ worth of rare lapis lazuli paint from a London supplier in order to produce an authentic Vermeer blue. And he had painted over a 17th-century canvas, carefully scrubbed of its surface pigments but retaining its distinctive pattern of cracking.

Then there was the simplest test of all: was the paint soft? The challenge for anyone who wants to forge an Old Master is that oil paints take half a century to dry completely. Yet the paint on Emmaus was hard, a sign that it was centuries old. Van Meegeren had figured out a way to mix 17th-century oil paints with a very 20th-century material: phenol formaldehyde, a resin that when gently cooked for two hours turned into Bakelite. No wonder the paint was unyielding: it was infused with industrial plastic.

Bredius had half a dozen subtle reasons to believe that “Emmaus” was a Vermeer. They were enough to dismiss one glaring reason to believe otherwise: that the picture doesn’t look like anything else Vermeer ever painted.

Think back to Bredius’s extraordinary rave review in The Burlington Magazine: “We have here — I am inclined to say — the masterpiece of Johannes Vermeer of Delft . . . quite different from all his other paintings and yet every inch a Vermeer.”

“Quite different from all his other paintings” — shouldn’t that be a warning? But the old man desperately wanted to believe that this painting was the Vermeer he’d been looking for all his life, the one that would provide the link back to Caravaggio himself. Van Meegeren set a trap into which only a true expert could stumble. Wishful thinking did the rest.

The authorities responsible for bringing Van Meegeren to justice unwittingly helped make his story world-famous. Forensic chemists quickly verified that, as Van Meegeren claimed, the paintings were hardened with Bakelite and aged with India ink. But in an absurd stunt, prosecutors challenged Van Meegeren to prove that he was the forger by painting a picture in the style of “Emmaus”. And of course he did, taking the opportunity to charm some journalists along the way. One breathless headline reported “He Paints for His Life”.

Newspapers in the Netherlands and around the world couldn’t tear their gaze away from the great showman. By the time the trial came, in 1947, the charge was forgery, not treason. When Van Meegeren himself took the stand, he explained that he had only forged the art to prove his worth as an artist and to unmask the art experts as fools.

“You sold these fakes for high prices,” admonished the judge.

“Had I sold them for low prices,” quipped Van Meegeren, “it would have been obvious they were fake.”

Peals of laughter rang out. In his closing statement, Van Meegeren claimed again that he hadn’t done it for the money, which had brought him nothing but trouble. It is a bold statement from a man who hosted wild sex parties while Amsterdam starved. But the newspapers and the public were just as spellbound as Bredius had been.

Found guilty of forgery, Van Meegeren was cheered as he left the courtroom. A Dutch opinion poll found that he was one of the most popular men in the country.

And that was the end of Van Meegeren’s adventure. A few days after being sentenced, he was admitted to hospital with heart trouble. He died shortly after, having never served a day of his prison term. For a while, there was even talk of putting up a statue.

Any of us is capable of falling for a lie. There is no guaranteed method of keeping ourselves safe — except to believe nothing at all, a corrosive cynicism which is even worse than gullibility. But I can offer a simple habit of mind that I have found helpful. When you are asked to believe something — a newspaper headline, a statistic, a claim on social media — stop for a moment and notice your own feelings. Are you feeling defensive, vindicated, angry, smug? Whatever the emotional reaction, take note of it. Having done so, you may be thinking more clearly already.

So what is your emotional reaction to the story of the clever forger who fooled the experts and scammed the Nazis? Van Meegeren’s early biographers fell in love with him. More recently we have learnt the truth.

Jonathan Lopez’s book The Man Who Made Vermeers is one of few to focus on the demonstrable fact that this likeable rogue was a Nazi. The circumstantial evidence is suggestive enough. Van Meegeren had prospered mightily under Nazi occupation, buying up a portfolio of expensive properties and holding decadent parties. You don’t get to act like that in German-occupied territory unless you’ve made friends with a few Nazis.

But it is the documentary evidence that is really telling. The most vivid is Teekeningen 1, a sinister and grotesque anti‑Semitic book illustrated and published by Van Meegeren. (Lopez hides his copy; he doesn’t want visitors to see it.) The book is packed with Nazi iconography and, despite the wartime privations of Amsterdam, lavishly produced.

No wonder, given whom Van Meegeren hoped might read it. A copy was hand-delivered to Adolf Hitler, with a handwritten dedication in artists’ charcoal: “To my beloved Führer in grateful tribute — Han van Meegeren.”

It was found in Adolf Hitler’s library.

What would have happened if this shocking discovery had emerged before Van Meegeren’s trial?

The discomfiting truth is that it did. A Dutch resistance newspaper published the news and Van Meegeren waved it away, claiming that he had signed hundreds of copies of the book and the dedication must have been added by someone else. It’s a ludicrous excuse. But people wanted to believe it. Wishful thinking is a powerful thing.

Caught in a scandal, a modern-day Van Meegeren would say, “That’s not my voice on the tape,” or call the story “fake news”. And their supporters would agree. It seems that if you show people a trickster with a sense of humour, a penchant for mocking experts and the capacity to land a few blows on a hated enemy, they will forgive a lot. What they cannot forgive they will find ways to ignore. Recent experience has only reinforced that lesson.

Han van Meegeren sensed that the Dutch people wanted a new story as desperately as Abraham Bredius had wanted to discover a new Vermeer. This tale would be upbeat, a light-hearted yarn of boldness and trickery in which a Dutchman had struck back against the Nazis. Han van Meegeren knew how to give people what they wanted.

In light of recent years, we shouldn’t be surprised. The facts about Van Meegeren seemed obvious enough. But facts are not the only thing that shape our thinking. Abraham Bredius was right all along when he wrote, “I had difficulty controlling my emotions.”

So do we all.

This essay draws on ideas explored in Tim Harford’s book ‘How to Make the World Add Up’ (UK)/‘The Data Detective’ (published this week in the US)

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