President Donald Trump’s decision to brag in a tweet about the size of his “nuclear button” compared with North Korea’s was widely condemned as bellicose and reckless. The comments are also part of a larger pattern of odd and often alarming behavior for a person in the nation’s highest office.

Trump’s grandiosity and impulsivity has made him a constant subject of speculation among those concerned with his mental health. But after more than a year of talking to doctors and researchers about whether and how the cognitive sciences could offer a lens to explain Trump’s behavior, I’ve come to believe there should be a role for professional evaluation beyond speculating from afar.

I’m not alone. Viewers of Trump’s recent speeches have begun noticing minor abnormalities in his movements. In November, he used his free hand to steady a small Fiji bottle as he brought it to his mouth. Onlookers described the movement as “awkward” and made jokes about hand size. Some called out Trump for doing the exact thing he had mocked Senator Marco Rubio for during the presidential primary—conspicuously drinking water during a speech.

The Amazon HQ2 saga had all the hallmarks of the gaudiest reality TV. It was an absurd spectacle, concluding with a plot twist, which revealed a deep and dark truth about the modern world.

Fourteen months ago, Amazon announced a national beauty contest, in which North American cities could apply to win the honor of landing the retailer’s second headquarters. The prize: 50,000 employees and the glory of housing an international tech giant. The cost? Just several billion dollars in tax incentives and a potential face-lift to the host city. Then last week, in a classic late-episode shock, several news outlets reported that Amazon would split its second headquarters between Crystal City, a suburban neighborhood near Washington, D.C., and Long Island City, in Queens, New York.

Why, exactly, did Donald Trump not join Emmanuel Macron, Angela Merkel, and Justin Trudeau at Saturday’s commemoration of the 100th anniversary of the original Armistice Day? I don’t know, and I don’t think anyone outside the White House does at this point.

What I do know is that one hypothesis that has shown up in many stories about his no-show—that Marine One, the presidential helicopter, “can’t fly” in the rain—doesn’t make sense.

As you’re looking for explanations, you can dismiss this one. Helicopters can fly just fine in the rain, and in conditions way worse than prevailed in Paris on November 10.

First, about helicopters and weather. (What follows is based on my having held an instrument rating as an airplane pilot for the past 20 years, and having worked in the Carter-era White House and occasionally having been aboard the Marine One of that era.)

If you gauge the climate inside the Democratic Party merely by which candidates won its 2018 primaries, you might think reports of its leftward lurch are exaggerated. Despite the hoopla about Alexandria Ocasio-Cortez’s and Ayanna Pressley’s upset victories in congressional races in New York and Massachusetts, not a single incumbent Democratic governor or senator lost a primary to a left-leaning challenger.

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But who wins an election is often less important than who sets the agenda. And ideologically, the Democratic Party has veered so sharply that “establishment” or “centrist” Democrats now frequently support larger expansions of government, and more vehemently scorn Big Business and Big Finance, than most liberal Democrats did a few years ago. In 2016, Hillary Clinton said a single-payer health-care system “will never, ever come to pass.” In 2017, West Virginia’s Joe Manchin, by some measures the most conservative Democrat in the Senate, said the idea “should be explored.” During the 2013–14 election cycle, Senator Cory Booker of New Jersey received more money from Wall Street than any other member of Congress. This February, he announced that he would no longer accept donations from corporate political-action committees.

This is a story about what happens when you limit birthright citizenship and stir up hate against a certain class of immigrants. It takes place in the Dominican Republic. Like most countries in the Americas, for a century and a half the Caribbean nation’s constitution guaranteed birthright citizenship for anyone born on its soil, with a couple of exceptions: the children of diplomats and short-term travelers. And like most other peoples in the Americas, Dominicans have had a more complicated relationship with immigration than the framers of that constitution might have anticipated.

The Dominican Republic has long been dependent on a steady stream of cheap immigrant labor that cuts its sugar cane, builds its buildings, and staffs the beach resorts that draw in billions of foreign dollars a year. Almost all of that labor comes from the only country close enough, and poor enough, to have people who want to immigrate in large numbers to the Dominican Republic: its Hispaniolan twin, Haiti. Some working-class Dominicans without clear Haitian roots resent poorer neighbors willing to accept lower wages and tough conditions. Many wealthy Dominicans who profit wildly off the cheap labor supply are eager to have strict immigration laws in place, too—not because they want less immigration, but because they want a freer hand. Immigrants in the country illegally have no protection from workplace regulations and can be rounded up, deported, and replaced whenever convenient—including right before payday. (Sound familiar?)

With the United States starkly divided and with many Americans asking what kind of nation we are, it seems a good moment to look back to November 1863 in Gettysburg, Pennsylvania, when Abraham Lincoln tried to answer the same question. Consecrating a Civil War battlefield where thousands of young men and boys had died four months before, he spoke of a nation “conceived in liberty, and dedicated to the proposition that all men are created equal.” For most Americans since, and for much of the world, those words have at­tained the status of scripture. We draw our sense of collective identity from them. They were, however, not strictly true, and Lincoln knew it.

Updated on November 12 at 1:12 p.m.

It’s November 4, 2020. Across the United States—and across the globe—liberals and Donald Trump–opposing conservatives alike drag themselves from fitful sleep, red-eyed and exhausted, filled with dread, incomprehension, and déjà vu. How did he do it again?

The night before, Trump had won reelection as president—despite a chaotic and frustrating first term, multiple investigations, and a historically low approval rating. Of course, Trump had won in 2016 despite many of the same weaknesses, but that win was thought to be a fluke, a product of a weak Democratic candidate, Russian interference, and Trump’s novelty. His critics never imagined lightning could strike a second time.

This year will mark the passing of a full century since the end of World War I—a hundred years since the “War to End All Wars.” In that time, much of the battle-ravaged landscape along the Western Front has been reclaimed by nature or returned to farmland, and the scars of the war are disappearing. Some zones remain toxic a century later, and others are still littered with unexploded ordnance, closed off to the public. But across France and Belgium, significant battlefields and ruins were preserved as monuments, and farm fields that became battlegrounds ended up as vast cemeteries. In these places, the visible physical damage to the landscape remains as evidence of the phenomenal violence and destruction that took so many lives so long ago.

Editor’s Note: In the comic below, Stan Lee offers a powerful definition of the American idea, illustrated by Anthony Winn. This piece was first published in The Atlantic’s 150th anniversary issue in November 2007.

In September 1862, the future Supreme Court Justice Oliver Wendell Holmes Jr. was one of 22,717 men who fell during the Battle of Antietam. His father, Oliver Sr., set out on an epic journey to find him and, a couple of months later, wrote about it for The Atlantic.

“My Hunt After the Captain” is an incredible firsthand account of what Maryland looked and felt like just after the bloodiest battle of the Civil War. Holmes describes what he saw on the streets of Frederick: “Delicate boys, with more spirit than strength, flushed with fever or pale with exhaustion or haggard with suffering, dragged their weary limbs along as if each step would exhaust their slender store of strength.” He notes what the ground looked like after the battle, with “dark red patches where a pool of blood had curdled and caked, as some poor fellow poured his life out on the sod.”