Just about everyone agrees that the post-World-War-II order of institutions and alliances that the United States built and guided over seven decades is under siege and threatened.

It’s a system of economic and security ties that expanded global prosperity and spread Western values of democratic governance and human rights around the world.

But this weekend in Canada, at the annual summit of the Group of Seven advanced economies – part of the constellation of organizations making up the US-led order – there is less unity over who and what forces are responsible for the weakening of that system.

For President Trump – who just last week slapped tariffs on steel and aluminum imports on five of the other six countries whose leaders he’ll be sitting down with in Quebec (the US already hit the sixth, Japan, with tariffs earlier this year) – the fault lies largely with the allies and partners who have profited from the economic and security order at America’s expense.

To this way of thinking, American taxpayers have paid for European and Asian allies’ security, while American workers have paid dearly for the world’s economic prosperity through their exported jobs.

But for America’s closest partners, and for many analysts who specialize in the challenges facing the US-led order, the responsible party is Mr. Trump himself – and more broadly a retreat of American leadership into nationalist economics and protectionism, and away from the international leadership role the US has played for 70 years.

Even before boarding his early morning flight to Canada, Trump, via remarks to reporters, fired off a proposal sure to further antagonize American allies: his recommendation that Russia, ousted from what was then the G8 four years ago over its annexation of the Crimea, should be readmitted.

Trump's off-the-cuff proposal may especially rile Europeans – perhaps its purpose – who have stuck with costly sanctions on Russia largely at America's behest. More broadly, Trump's call to re-admit Vladimir Putin's Russia to the Western leaders' club will raise doubts about Trump's understanding of the role the G7 has played and about US leadership of the international system.

The leaders Trump will meet in Quebec were already dismayed by his withdrawal of the US from the Paris Climate Accords and the Joint Comprehensive Plan of Action, known better as the Iran nuclear deal, and by his threats to weaken US participation in NATO and Asian security alliances.

Andrew Vaughan/The Canadian Press/AP

President Trump salutes as he arrives for the G7 Summit June 8, 2018, at Canadian Forces Base, Bagotville, Canada.

But it was the Trump administration’s imposing of tariffs against European countries, Canada, and Mexico, last week on national security grounds that most sharply stung some allied leaders.

Trump’s decision represented a shift away from the more traditional postwar interpretation of allies like NATO partners as “reliable” sources of essential materials like steel for defense industries, to more of a go-it-alone reliance on domestic producers.

That action also raised the specter not just of a trade war among friends but of a waning Western order weakened from within – and more immediately of what some are fearing will unfold as the “G6 + 1” summit, with Trump’s America the odd man out.

“I do think we have reached a little bit of a Rubicon moment over whether the United States is going to turn its back on this economic order,” says Thomas Wright, director of the Brookings Institution’s Center on the United States and Europe in Washington.

Issues ‘can be worked out’

At the same time, no one expects the G7 summit ending Saturday to mark a watershed moment for the Western alliance – with either a resolution of the trade frictions or with a full-blown falling-out between the US and its allies.

Larry Kudlow, Trump’s top economic adviser, told reporters this week that the discord the president is likely to encounter among G7 leaders would be akin to a “family quarrel” over issues that “can be worked out.”

For one thing, Trump is likely to be preoccupied with his historic summit just days away with North Korean leader Kim Jong-un, some experts say. Trump has reportedly told aides that he feels the G7 meeting will be a distraction before the Singapore summit with Kim.

Moreover, the G7 host, Canadian Prime Minister Justin Trudeau, can be expected to try to downplay the elite club’s rifts and focus on common interests, analysts add. As Canada’s leader, Mr. Trudeau has been blunt in his criticism of Trump’s “national security” tariffs. But some see him redirecting to messages of unity as he greets his guests.

“Justin Trudeau would clearly like to avoid a G6 + 1,” says Samantha Gross, a fellow in climate and energy policy at Brookings. Still, she worries that the deep divisions, including over tariffs and broader trade policy, could sideline the more unifying topics Trudeau might wish to highlight.

The falling out between the US and its allies ratcheted up a few notches Thursday, when French President Emmanuel Macron – received at the White House in late April as Trump’s BFF – threatened to isolate Trump at the G7 by pushing for a rebuke of the US over the tariffs.

Trump’s response? Bring it on. Hurling back accusations that Mr. Macron and Trudeau are “charging the US massive tariffs” and “keeping our farmers out,” Trump tweeted, “Look forward to seeing them tomorrow.”

What’s good for America

Administration officials say that, even if the president and his national security advisers seem focused on North Korea’s denuclearization right now, the challenges facing the West and the US-led global order have been at the top of the Trump administration’s agenda from Day 1.

They point to documents like Trump’s first National Security Strategy and National Defense Strategy, which zero in on the aggressive challenges that non-Western “big powers” – namely Russia and China – are ramping up to undermine and supplant the US-led order of private-enterprise-based economies and liberal democracies.

But the US cannot continue to lead this international order if its outcome is greater global prosperity at America’s expense, these officials add – thus the Trump argument that Western allies and partners who have benefited from the postwar system need to step up and pay more as America refortifies itself at home.

“A strong America is good for Americans, but it is also good for our allies and for the world,” the State Department’s top Europe diplomat, Wess Mitchell, said in a speech at Washington’s Heritage Foundation this week.

“American strength is the foundation upon which the world as we know it rests,” Secretary Mitchell said, “and if that foundation is vulnerable, all we believe in, all that we ground our strength upon – democracy, markets, deterrence – all of that is vulnerable as well.”

Moreover, Mitchell suggested that the actions Trump has taken that have separated the US from its chief allies – whether exiting the Iran deal or imposing steel tariffs – are aimed at strengthening America so it can better defend the West against common enemies.

“In taking strong positions, we are not targeting our allies,” he said, underscoring “not.” Calling out Russia, China, and Iran, as the real threats “putting our collective security at risk,” he added, “We urge our allies to take these and other threats to Western security more seriously than they have in the past.”

Allies vs. adversaries

One problem some see with the Trump approach to rescuing (and leading) the West and the postwar order is that it mixes tough measures toward allies with outreach to adversaries like North Korea and Russia, Trump’s pre-flight comments Friday being a case in point.

“It’s this split-screen image where it’s growing tensions with our closest partners and allies and then … juxtapose that … with the White House seeking a summit with President Putin and looking to the good meeting with Kim Jong-un,” says Heather Conley, director of the Europe program at the Center for Strategic and International Studies in Washington. “It feels like we are treating our allies with contempt, while we are feting our adversaries.”

To be sure, there have been “family quarrels” before, as Mr. Kudlow, the economic adviser, suggests – within the G7 over US monetary policy, among NATO allies over the installation of US nuclear weapons in Europe, and more recently the Iraq war.

But those were disagreements over issues, Ms. Conley says, whereas now she says it’s the basis of the international order – American leadership of a community of like-minded nations – that is in question.

At each instance of squabbling until now “it was [over] an issue. It was not the fundamental underpinnings of the international system that the US created in the post-World War II environment. That is now what feels at stake,” she says, “and that’s what is different.”

Tony Gentile/Reuters

Five Star Movement leader Luigi Di Maio claps for the new Chamber of Deputies president Roberto Fico, also of Five Star, in Rome on March 24.

Maybe it’s because of Donald Trump, but when most people say “populist” they think right-wing nationalist, with a splash of authoritarianism. There are plenty of other political leaders around the world who fit that mold, from Indian Prime Minister Narendra Modi to Hungarian Prime Minister Viktor Orbán.

But the new Italian government, installed this week, shows that populism comes in other flavors too. Parties like the League and the Five Star Movement, the Italian ruling pair, may both wear the populist label, sharing a distrust of elites and a claim to embody “the people.” But that’s about where their similarities end.

Populism is in fact a broad category, ranging from the radical right to the revolutionary left, which takes nations in very different directions. While often spoken of in one breath, the disparate types of populists around the world have conflicting agendas – and similarly varying levels of success at carrying those agendas out.

And in Italy's case, the two populist parties' priority goals are so far apart that they they may end up achieving neither of them.

The League is a standard radical right-wing populist party that campaigns against Italy’s traditional political and cultural elites and against immigrants. It is popular among small businessmen and has much in common with Marine Le Pen’s National Front party in France.

But it has much less in common with its ally, the Five Star Movement founded by activist-comedian Beppe Grillo as a shout of rage against a corrupt and stagnant political class, which quickly found an echo among voters.

“At the beginning, Five Star had a very, very strong left-wing, Green [party] soul,” says Daniele Albertazzi, an Italian expert on populism at the University of Birmingham in Britain. “It was big on direct democracy and new technology empowering the people.”

Using the internet to do politics differently, Five Star has refused to be boxed into a traditional political category, even as it has adopted a harder line against immigration. “It is a cross-cutting, catch-all party that draws voters from the left, the right, and the center,” says Roberto D’Alimonte, a political analyst and pollster at LUISS, a university in Rome.

Its main policy planks would not be out of place in a European socialist program: environmental issues, and a sort of universal basic income that is extremely popular in Italy’s poor south, where Five Star won 42 percent of the vote in March’s elections.

But the idea of handing out money to poor southerners is not popular at all in the prosperous north, the League’s stronghold, where anti-immigrant sentiment extends to Italians living south of Rome. The League’s top priority is a flat tax of 10 percent.

Beyond the awkward math of raising welfare spending while slashing tax revenues, there is a matter of principle. The League was founded on the frustration that northern businessmen felt at being made to subsidize southerners. Now Five Star is asking the League to do just that.

“I have my doubts about how long this partnership will last,” says Professor D’Alimonte. “Their constituencies are so different.”

It's difficult, speaking for the people

Five Star’s hybrid appeal may be unique, but other populist movements have sprung up that promote left-wing agendas. More common in Latin America than elsewhere, Hugo Chávez’s Bolivarian Revolution in Venezuela is a prime example.

Like right-wing populists, left wingers focus their ire on the elites that they accuse of betraying “the people.” But, says Duncan McDonnell, a professor at Griffith University in Nathan, Australia who has written extensively on populism, leftists “do not argue that the people are threatened by dangerous ‘others’ such as immigrants or Roma” in the way their right-wing counterparts do.

Instead, they are more inclusive, says Dr. Albertazzi, using standard socialist policies “to bring people at the bottom of society into the community, by investing in health, education, and jobs.”

For a while that worked in Venezuela. While Mr. Chavez was president – until his death in 2013 – absolute poverty levels fell by two-thirds, unemployment halved, and infant mortality fell from 20 to 13 per 1,000 live births. But profligate spending and falling oil prices punctured the model, and Venezuela is now mired in economic chaos, with poverty levels rising again.

In Greece, the left-wing firebrand Alexis Tsipras has scarcely been more successful in keeping his promises to the poor. He won office at the head of the populist Syriza party, campaigning against the old-style politicians who had led Greece into economic ruin, and against the austerity policies that the European Union and International Monetary Fund were urging as a remedy.

In the end, in return for bailouts, Mr. Tsipras was obliged to cave to EU reform demands. Though he resolved the debt crisis, the reforms have not led to a significant recovery in an economy that has lost a quarter of its size.

Though leftists rarely adopt right wingers’ anti-foreign stance, left- and right-wing populists do share key attributes, says Professor McDonnell. “Populism posits a good homogenous people against a set of corrupt and distant elites who are oppressing them undemocratically so that their rights and prosperity are threatened,” he says.

And populists of all stripes “dislike the constraints that liberal democracy puts on them,” McDonnell adds, often showing little patience for the checks and balances that the separation of powers is meant to guarantee.

When you've won power, try to keep it

Chavez gave the most dramatic expression to that attitude, setting up a Constituent Assembly that he controlled to sideline the existing parliament and to pack the judiciary with his allies.

In Bolivia, President Evo Morales last year persuaded the country’s top court to strike down constitutional limits on re-election, thus allowing him to stand for a fourth term next year, and as often as he likes thereafter.

Such stories are not unfamiliar to voters in Hungary and Poland, where populist governments have instituted judicial reforms that appear to undermine the independence of the judiciary. Last November the deputy head of the European Commission, Frans Timmermans, warned that legislation passed by the Law and Justice party in Poland posed “a systemic threat to the rule of law” there.

In Hungary, Prime Minister Orbán has also pushed through reforms that weaken the Constitutional Court, putting his government on a collision course with the European Union. [Editor's note: The original version misidentified Mr. Orbán's office.]

“Populists say ‘if I’m speaking on behalf of the people, how can an unelected judge tell me what to do?’ ” explains Albertazzi. “They don’t have much time for liberal democratic procedures.”

Leftist populist governments have had a mixed record: Venezuela has collapsed into political and economic unrest under Chavez’s successor, Nicolás Maduro, while Bolivia under President Morales has enjoyed spectacular economic growth, slashing poverty and inequality. In Greece, the Syriza government’s failure to stand up to outside pressure “has tainted the broader model,” argues Cas Mudde, who studies populist movements at the University of Georgia in Athens.

Populists on the right, meanwhile, have the wind in their sails in Europe and beyond. It remains to be seen which direction the new Italian government, torn between different priorities, will take, says Franco Pavoncello, president of John Cabot University in Rome.

In Italy, he warns, “one of the worst things for a populist is to win the elections.”

Rogan Ward/Reuters

Former South African president Jacob Zuma waves to supporters outside the high court in Durban, South Africa, June 8, 2018.

There wasn’t much to it. In a cramped courtroom Friday morning, former South African president Jacob Zuma sat in the dock and listened quietly as the teams of lawyers in front of him asked to postpone his corruption trial for six more weeks to finish preparing their cases.

The judge said yes. The court adjourned. And not 20 minutes after he had shuffled into the courtroom, Mr. Zuma was walking back out into the bright winter sunlight, a smile cracking across his creased, round face.

For many South Africans, however, this simple moment was also a deeply symbolic one.

But exactly what it symbolizes is far less clear cut.  

For some, watching their former president appear in court to answer to charges of corruption, money-laundering, and racketeering is proof positive that their young democracy is capable of holding its leaders responsible for their misdeeds. On a continent where impunity for the powerful and well-connected has often been the norm, they say Zuma’s trial will offer a stern warning to would-be crooked politicians of the future.

“This is holding a very powerful person to account in an environment where that hasn’t often happened before, and that means a lot,” says David Lewis, the executive director of the South African nongovernmental organization Corruption Watch.

But for others, the fact that Mr. Zuma has been put on trial is a symbol of just how broken that system has become. They say that instead of focusing on flushing out the insidious and grinding forms of corruption that many South Africans face on a daily basis – like having to bribe police officers and doctors, or watching public money for their roads, schools, and hospitals disappear into the pockets of local officials – the country’s political leadership is using the former president’s prosecution as a smokescreen.

“There are all kinds of corruption in this country that we need to deal with, but instead we’re spending all this money and energy pinning the label on one man,” says Bishop Timothy Bheki Ngcobo, the provincial secretary of the National Interfaith Council of South Africa, who helped organize a vigil of Zuma’s supporters in Durban the night before the court case. (The government has spent more than $1.8 million on his legal fees, according to South Africa’s justice ministry.) “Corruption is becoming a word you use when you want to destroy someone’s image – it’s said without proof or interrogation.”

'Does it matter if he stole that money?'

That image of Zuma – as an underdog being victimized by a scheming political elite – is one the former president himself has long cultivated, says Sithembile Mbete, a political science lecturer at the University of Pretoria.

In fact, she says, it’s the very image that brought him to power in the first place.

In 2005, when Zuma was deputy president, his friend and business associate Schabir Shaik was convicted of funneling 4 million rand (more than a quarter million dollars by today’s exchange rate) from the French arm manufacturer Thales (formerly Thomson-CSF) to Zuma in exchange for facilitating a lucrative contract for the company to provide ships to the South African navy. The contract was part of a larger, scandal-ridden set of military purchases known collectively here as the “arms deal.”

Zuma was fired, and the country’s National Prosecuting Authority quickly moved to bring corruption charges against him as well.

But Zuma fought back, arguing the charges were politically motivated, a way for the then-president Thabo Mbeki and his allies to tarnish his name and destroy his career. Eventually, the charges were dropped, and soon after, Zuma became president.

“In a sense, it was these charges that helped bring Zuma to prominence and power,” Ms. Mbete says. “They made his reputation as a victim of the system.”

That reputation helped carry Zuma through nearly two terms of a presidency dogged by scandals and charges of economic mismanagement. But in February of this year, his party, the African National Congress, asked the president to step down, 14 months before the end of his term.

Many analysts believe the move was designed to help clean up the party’s image before general elections next year, which are expected to be the closest since the party first came to power 25 years ago. And reinstating the president’s corruption charges, both supporters and critics of Zuma say, was a way for the new administration of Cyril Ramaphosa to make a point about how serious it was about rooting out graft in government.

Both sides caught a glimpse of their version of Zuma Friday. In court, he appeared chastised and subdued, nodding politely as the judge addressed him sternly as “accused number 1.” But as soon as he stepped outside to greet the thousand or so supporters who had gathered in the road outside the courthouse, his mood flipped.  

“For many years, people have been saying, ‘Zuma is corrupt,’ but have they ever proved it?” he asked the crowd in Zulu, to loud cheers. Many in the audience wore t-shirts and carried posters reading “Hands off our president” and “Wenzeni uZuma” – What did Zuma do?”

Some were emphatic that Zuma was innocent. But for others, that wasn’t the point.

“There’s been corruption in South Africa since before Jacob Zuma was president, since before he was even born – why do people think they’ll get rid of it just by getting rid of him?” says Nellie, a hairdresser and nail artist from Durban who asked that her full name not be used because she says she is distrustful of how media has portrayed “the people’s president” and his supporters.

“Does it matter if he stole that money? Everyone in power steals money,” says Khethiwe Zulu, who runs a small construction company. “What matters is that he also did good things for poor people in this country. What matters is that he cares about us.”

Amanda Santizo sits on the edge of a foam mattress where her elderly mother is sleeping on Tuesday afternoon.

She says her mother is trying her best to accept the family’s new reality, following the eruption of the volcano Fuego on Sunday. They lost their home, livestock, and way of life.

“We had to leave everything behind when the Army evacuated the village,” Ms. Santizo says inside the crowded, noisy refuge in a Catholic church in the city of Escuintla, about nine miles from their village. 

The volcano’s sudden eruption left an estimated 109 people dead and another 200 or more are still missing. The death toll is likely to keep rising, authorities say.

The day after the eruption, as communities at the foot of Fuego searched and hoped for signs of life, President Jimmy Morales held a press conference in an affected town. 

“We would like to take this opportunity to ask people living in high risk areas to help us to prevent these situations,” he said. “There are many homes located close to rivers, close to ravines, on mountain slopes. We need everyone to cooperate.” 

To many, his words implied that the victims of the disaster were to blame for their fate. But that assumes a level of choice in housing and living environment that experts say rarely exists. Access to land in Guatemala has long been fraught: It was at the root of the 36-year civil war, and more recently, with the introduction of monoculture farming, land has become even more scarce.

The poor are frequently hardest hit by disasters around the world, often owing to factors as simple as the availability of quality housing, access to credit, and access to land. Tackling basic challenges like affordable housing, particularly within a few hours of urban areas where jobs are most prevalent, can have crucial effects on who suffers in a disaster, experts say.

“Poor people trade livability for economic opportunity,” says Sameh Wahba, the global director for urban and territorial development, disaster risk management, and resilience at the World Bank. “Housing and land markets are dysfunctional. And [the poor] are unable to find affordable housing and land” within a reasonable commute to large job markets, like cities.

Carlos Jasso/Reuters

Residents pause during a search in an area affected by the eruption of the Fuego volcano, in San Miguel Los Lotes, Guatemala, June 7, 2018.

Santizo says her parents moved to their village when she was eight years old. “My father was a peasant and he bought land [in the village of Santa Rosa] because it was cheap,” she says. 

Eufenia Garcia, who lived in San Miguel Los Lotes, the village closest to the volcano, lost 20 family members in the deadly avalanche of mud and volcanic matter on Sunday. Her family lived there for 32 years. 

Both women say they knew the volcano was active, but were so used to seeing a cloud above the crater that they didn’t fear an eruption.

High-risk homes

According to official statistics, 52.8 percent of Guatemalans live below the poverty line, and almost half of all Guatemalans living in urban areas live in informally-built slums. In Escuintla, the department where the Fuego volcano is located, half of the population are poor, and poverty increased by nearly 12 percent between 2006 and 2014.

Nationwide, 1.2 million Guatemalans don’t have access to safe housing. About 61 percent of that number live in sub-standard housing: tiny shacks with tin roofs located on mountain slopes, ravines, or urban slums, and with no running water or electricity.  

“Many farm workers are forced to [move] due to a lack of opportunities and land tenure issues. They don’t have title deeds and lack access to credit, among other limitations,” says Víctor Velásquez, director of the Guatemalan chapter of Habitat for Humanity, an international nongovernmental organization that seeks to provide decent and affordable housing for the poor. He says people don’t live at the foot of a volcano or in a river gulley or other risky zones by choice. 

Fuego’s eruption was the latest in a long series of deadly natural disasters that have claimed the lives of Guatemalans living on at-risk land. 

In October 2015, a landslide in El Cambray Dos, a working-class neighborhood outside of Guatemala City, left 280 people dead and 70 disappeared. Former Mayors Antonio Coro and Víctor Alvarizaes face criminal charges for ignoring reports from Guatemala’s disaster agency that said there was an imminent threat to families living in the area due to erosion. A year later, survivors were still living in an overcrowded shelter, searching for permanent housing. 

Marcel Arévalo, coordinator of the poverty and migration studies department of the Latin American Social Sciences Institute, blames the rapid expansion of single-crop agriculture for the displacement of peasants such as Santizo and her family.  

“Throughout the country’s history, the rural and indigenous population has been continuously dispossessed of its land and pushed to the mountain slopes and other high risk areas by an economic model based on agricultural exports,” says Mr. Arévalo.

He says it dates back to colonial times, starting with coffee, then bananas. “Now, it’s sugarcane and African palm” that are taking over land, because of their lucrative export price, he says. 

According to the National Institute of Statistics, the total surface area taken up by African palm monocultures increased by 33 percent from 2013 to 2014, whereas beans, a dietary staple for the rural poor, decreased by 70 percent. 

Mr. Wahba from the World Bank says that as climate change continues, along with a rise in the frequency of natural disasters; governments, civil society, and local communities are trying to find solutions. His team, for example, used to work more in disaster recovery, but today are focusing largely on risk identification, mapping, and risk reduction. 

But “risk management will only be effective if it’s operating at various levels of society,” Wahba says. “Community-level work is increasing significantly,” such as programs in Colombia and Brazil where community members are “hired” by local governments to keep tabs on at-risk land, like steep cliffs or dried riverbeds, near where they live. They’re charged with protecting the environmental resources in their community and preventing informal housing from going up on precarious land, Wahba says.

Rescue efforts are still active but have been hampered by sudden evacuations, as it is feared the volcano could erupt again any minute. Although the ground in the villages surrounding the volcano is still covered in hot ash, the air has a overpowering sulfurous odor, and the crater is still giving off thick, black smoke. Some evacuees are risking their lives to return in search for loved ones or to retrieve their animals and belongings. 

Faustino Pachac, a seasonal farmer, and his wife, Carmen Corado, returned to hard-hit San Miguel Los Lotes this week after hearing rumors that homes were being looted after the evacuation. 

“If no one helps us, we have to stay where we are,” Ms. Corado says, adding that she feels she has no other choice but to return to the village. “Where else are we supposed to go?”

Whitney Eulich contributed reporting from Mexico City.   

Greg Gibson/AP/File

President Clinton sits in the Map Room of the White House in Washington on August 17, 1998, before confessing to the American people about his relationship with former intern Monica Lewinsky.

If you’ve ever held a political conviction, you’ve probably found yourself asking, “How on Earth can those people be so gullible?”

Not your people, of course, the reasonable and well-informed ones who share your politics. No, we mean the millions on the other side, the ones who have chosen to stick their tinfoil-covered heads in the sand to swallow the tripe-flavored Kool-Aid. Those people. 

Except it turns out that, under the right conditions, any of us can be played. Behavioral scientists say that many of our beliefs about the world, true as they may be, are more likely to be determined by something other than our power to discriminate truth from fiction. And that’s not necessarily a bad thing.

“There's significant evidence that we evolved as a cooperative species, and trust is central to that,” says Pamela Paxton, a sociologist at the University of Texas at Austin who studies social capital. “There are a lot of benefits that we get, even in terms of efficiency, from high levels of trust.”

A bias toward belief

It all has to do with the way we process information. Until relatively recently, most psychologists implicitly adopted a model of thought developed in the 17th century by French philosopher René Descartes, who, in his “Fourth Meditation,” divided the process of believing into two distinct faculties. First, what he called the “intellect” comprehends an idea. Next, the intellect presents the idea to the “will,” which then attempts to determine whether the idea is true or not.

Descartes’s model makes intuitive sense, but beginning in the late 1980s and early 1990s, psychologists began to see flaws with it. A series of experiments, led by psychologist Daniel Gilbert, that distracted participants while asking them to identify sets of true and false sentences found that the distraction interfered with the participants’ ability to identify the false statements, but not the true ones.

Dr. Gilbert proposed a different model of believing, one consistent with that of Descartes’s rival, the Dutch philosopher Baruch (Benedict) Spinoza, who proposed that comprehending an idea and believing it to be true are actually the same process. Rejecting an idea, Spinoza said, requires an additional step that uses up additional mental resources.

Put another way, a belief is like an automatic email newsletter: you have to go out of your way to figure out how to unsubscribe.

From an efficiency standpoint, this arrangement makes sense. “If you're trying to determine whether something you heard is true or false,” says Lisa Fazio, a psychologist at Vanderbilt University in Nashville, Tenn., “you can do this kind of labor-intensive search through your long-term memory to see what you know about the topic and whether or not it seems reasonable, or you can just go with this kind of gut-level feeling of, ‘That seems true.’ ”

And your gut works just fine, in most cases. “Most of the time, most humans are trying to tell each other things that are true and useful to them,” says Gus Cooney a researcher at Harvard University in Cambridge, Mass., who studies the psychology of conversations. Dr. Cooney says he suspects that this was even more true in our distant evolutionary past, when humans lived in small, stable groups and there was no advertising.

In the modern world, however, our natural credulity can be hacked. “The problem comes when we when we take that rule that's useful in one domain and then we misapply in a domain where people are trying to intentionally mislead us,” says Cooney.

Say it again

The top three most common hacks, exploited by politicians for centuries, are repetition, repetition, and repetition. The more times we hear an assertion, say psychologists, the less effort it takes to wrap our minds around it, and humans, for some reason, confuse that ease with truthfulness.

“If you just repeat things,” says Professor Fazio, “you can make them gain this processing fluency while not actually changing the truth of the statement.”

So does this mean that the solution to political misinformation is for people to become less trusting of each other? Probably not. “Trust eases interactions between people,” says Professor Paxton, “so you don't have to rely on third parties to ensure or watch or regulate.”

Indeed, in 2010 economists found that places that rank high in interpersonal trust, such as the Nordic countries, generally have fewer barriers to starting a business than low-trusting countries, such as Brazil and Uganda. More importantly, people living in more trusting societies generally say they are happier.

In the United States, trust has been steadily declining over the past 40 years, a phenomenon that Paxton attributes in part to headline-grabbing scandals. “I suspect it may just be that, with more and more news,” she says, “we're just more aware constantly of negative information about institutions.”

Instead of harboring mistrust, Fazio suggests that, when you’re presented with a statement, you can “pause and think about it.”

“The one thing that we found that helps people to notice these errors, is to really slow down and read the article, like a fact checker where they have to circle the errors in the story,” she says. “And those things work.”

But even this method, says Fazio, won’t catch every factual error. There’s no perfect solution, which means that we’ll have to learn to live with some of us being wrong sometimes.

“Of course I'd love people to be more skeptical, and approach the world like empiricists and scientists,” says Cooney. “But I think being a little more humble and a little more tolerant might be the right answer.”

Spinoza, who lived through the end of a bloody religious war that consumed most of Europe, likely would have agreed. In his “Ethics,” written in 1664 or 1665, he wrote that his doctrine that seeing and believing are one and the same ”teaches us to hate no man, neither to despise, to deride, to envy, or to be angry with any.”

AP Photo

Political prisoners wave in jubilation prior to their release June 1 from Helicoide prison in Caracas, Venezuela. Venezuelan officials said they are releasing 39 jailed activists in a gesture aimed at uniting a fractured nation.

A majority of nations in Latin America took an extraordinary step this week to solve a crisis in Venezuela that is literally spilling across their borders. At a meeting of the Organization of American States (OAS), they stated that a May 20 presidential election in Venezuela lacked legitimacy because it violated so many democratic norms.

In effect, countries representing most of Latin America’s population declared that President Nicolás Maduro is not the legitimate leader of Venezuela. The vote was a neighborly rebuke of a country drifting toward total dictatorship and economic ruin.

In the past two years, more than 2 million people have fled Venezuela to other parts of Latin America. The exodus has reinforced the idea that the region cannot ignore a loss of liberties in nearby countries. Mr. Maduro has jailed his main opponents and created a migration crisis out of his mangled management of a once-wealthy economy.

The vote against Maduro was made easier by the fact that the Lima Group, a body of 13 Latin American and Caribbean governments, plus Canada, was negotiating with him last year to hold off on an election until a free and fair process could be ensured. He ignored the request and called the election in May. Even though the election lacked “the necessary guarantees for a free, fair, transparent and democratic process,” as the OAS stated, Maduro claimed he won another six-year term.

The OAS vote on June 5 was not only a moral statement. It could now embolden a few Latin American countries to follow the United States and European Union in placing financial sanctions on top Venezuelan leaders. The EU, too, might stiffen its sanctions.

Latin America’s response is another example of how regional bodies – rather than the West or United Nations – can exert pressure on one of their own to follow democratic norms. Groupings in Africa and Southeast Asia, not to mention the EU, have sometimes shown the backbone to coax a neighbor away from an authoritarian path.

Calling out Maduro on his legitimacy as a ruler may also embolden his domestic opponents. While the regime holds the guns, the political opposition needs moral ammunition. With so many Venezuelans flooding the region, the OAS finally had to act. Telling the truth about a sham election may help puncture a big lie that keeps Maduro in power.