Representative Alexandria Ocasio-Cortez, one of the most prominent progressive politicians in the country, warned last week that her hometown is at high risk of having a decidedly moderate mayor. Standing in New York’s City Hall Park to deliver a last-minute endorsement of Maya Wiley, a civil-rights lawyer who’d previously struggled to crack the top tier, Ocasio-Cortez urged the left to come together. “We have the candidates in the field, and it’s time for us to make a choice,” she said. “We cannot afford to sit on the sidelines. We can’t afford to not engage because of what could have been. We engage in the world that we have.”

The forces driving a likely moderate outcome in the June 22 Democratic primary are varied; many are specific to New York and to this election. But the race also contains major warning signs for progressives across the country. If the left loses out in the city arguably leading the socialist revival in the United States, it will be, at least in part, because of dramatic infighting fueled by rigid positions on sexual and social-justice politics, as well as the generalized failure to unify behind one candidate alluded to by Ocasio-Cortez.

Nations, like individuals, tell stories in order to understand what they are, where they come from, and what they want to be. National narratives, like personal ones, are prone to sentimentality, grievance, pride, shame, self-blindness. There is never just one—they compete and constantly change. The most durable narratives are not the ones that stand up best to fact-checking. They’re the ones that address our deepest needs and desires. Americans know by now that democracy depends on a baseline of shared reality—when facts become fungible, we’re lost. But just as no one can live a happy and productive life in nonstop self-criticism, nations require more than facts—they need stories that convey a moral identity. The long gaze in the mirror has to end in self-respect or it will swallow us up.

Carl Schoonover and Andrew Fink are confused. As neuroscientists, they know that the brain must be flexible but not too flexible. It must rewire itself in the face of new experiences, but must also consistently represent the features of the external world. How? The relatively simple explanation found in neuroscience textbooks is that specific groups of neurons reliably fire when their owner smells a rose, sees a sunset, or hears a bell. These representations—these patterns of neural firing—presumably stay the same from one moment to the next. But as Schoonover, Fink, and others have found, they sometimes don’t. They change—and to a confusing and unexpected extent.

Schoonover, Fink, and their colleagues from Columbia University allowed mice to sniff the same odors over several days and weeks, and recorded the activity of neurons in the rodents’ piriform cortex—a brain region involved in identifying smells. At a given moment, each odor caused a distinctive group of neurons in this region to fire. But as time went on, the makeup of these groups slowly changed. Some neurons stopped responding to the smells; others started. After a month, each group was almost completely different. Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time.

In recent years, demographers and pundits have latched on to the idea that, within a generation, the United States will inevitably become a majority-minority nation, with nonwhite people outnumbering white people. In the minds of many Americans, this ethno-racial transition betokens political, cultural, and social upheaval, because a white majority has dominated the nation since its founding. But our research on immigration, public opinion, and racial demography reveals something quite different: By softening and blurring racial and ethnic lines, diversity is bringing Americans together more than it is tearing the country apart.

The majority-minority narrative contributes to our national polarization. Its depiction of a society fractured in two, with one side rising while the other subsides, is inherently divisive because it implies winners and losers. It has bolstered white anxiety and resentment of supposedly ascendant minority groups, and has turned people against democratic institutions that many conservative white Americans and politicians consider complicit in illegitimate minority empowerment. At the extreme, it nurtures conspiratorial beliefs in a racist “replacement” theory, which holds that elites are working to replace white people with minority immigrants in a “stolen America.”

Editor’s Note: Every Tuesday, Abby Freireich and Brian Platzer take questions from readers about their kids’ education. Have one? Email them at homeroom@theatlantic.com.

Dear Abby and Brian,

Everything feels untenable. I am so frustrated for my son, whom I’ll refer to as “Caleb,” who is in first grade. I’m frustrated for his teachers too, and for me and my wife. Caleb is on the verge of tears by the time online school ends at 2:30, and, to be honest, so am I. His schedule is different every day, and he can’t read well enough to follow all the directions, so even though I am working and ignoring him most of the time, he interrupts me just often enough to make me seem unprofessional. After his day is done, we let him watch TV until my wife or I can stop working, which is around 5 o’clock most days. This means that one of us has about an hour with Caleb before bath, dinner, and bedtime.

During a pandemic, no one’s health is fully in their own hands. No field should understand that more deeply than public health, a discipline distinct from medicine. Whereas doctors and nurses treat sick individuals in front of them, public-health practitioners work to prevent sickness in entire populations. They are expected to think big. They know that infectious diseases are always collective problems because they are infectious. An individual’s choices can ripple outward to affect cities, countries, and continents; one sick person can seed a hemisphere’s worth of cases. In turn, each person’s odds of falling ill depend on the choices of everyone around them—and on societal factors, such as poverty and discrimination, that lie beyond their control.

This article was published online on June 7, 2021.

“Nothing can go wrong!” Boris Johnson said, jumping into the driver’s seat of a tram he was about to take for a test ride. “Nothing. Can. Go. Wrong.”

The prime minister was visiting a factory outside Birmingham, campaigning on behalf of the local mayor ahead of “Super Thursday”—a spate of elections across England, Scotland, and Wales in early May. These elections would give voters a chance to have their say on Johnson’s two years in office, during which quite a lot did go wrong.

Johnson was, as usual, unkempt and amused, a tornado of bonhomie in a country where politicians tend to be phlegmatic and self-serious, if not dour and awkward. Walking in, he had launched into a limerick about a man named Dan who likes to ride trams. The mayor, Andy Street, looked horrified, tomorrow’s disastrous headlines seeming to flash before his eyes. (The limerick, I’m sorry to say, was not at all filthy.)

This article was published online on June 9, 2021.

Back when commuting was a requirement for going to work, I once passed through a subway tunnel so filthy and crowded that the poem inscribed on its ceiling seemed like a cruel joke. “Overslept, / so tired. / If late, / get fired. / Why bother? / Why the pain? / Just go home / do it again.” “The Commuter’s Lament,” which adorns a subterranean passage in New York City’s 42nd Street station, made the already grim ritual of getting to and from work positively Dante-esque. But no one questioned the gist of it. The commute, according to the Nobel Prize–winning economist Daniel Kahneman’s research, ranked as the single most miserable part of our day. A Swiss study held long commutes responsible for “systematically lower subjective well-being.”

“How to Build a Life” is a weekly column by Arthur Brooks, tackling questions of meaning and happiness.

For many people, the cruelest part of daily life is the transition between wakefulness and sleep. When you should be sleeping, you want to be awake; when you should be awake, you want to stay asleep. It is easy to regard sleep as a torment: hard to attain and then hard to give up, day after day after day.

According to the CDC, about 70 million Americans have chronic sleep problems. Insomnia affects between a third and a half of U.S. adults at one point or another. And we Americans are not unusually afflicted—one 2016 study reported that worldwide, 10 to 30 percent of the population experiences insomnia; some studies find rates as high as 50 to 60 percent.

Updated at 6:54 p.m. ET on June 28, 2019.

The numbers used to assess health are, for the most part, not helpful.

There are the vital signs: heart and respiratory rates and body temperature. Sometimes blood pressure. These are crucial in emergencies. If you’ve been stabbed in the chest, paramedics want to know no numbers more than these.

But in day-to-day life, the normalcy of those numbers is expected. It doesn’t so much grant you a clean bill of health as indicate that you are not in acute danger. What if you just generally want to know whether you’re on pace to live an average life or longer?

The most common numbers are age and body weight. The U.S. health-care system places tremendous value on the latter, in the form of body-mass index, or BMI, a simple ratio of weight over height. BMI is used to define obesity and “overweight,” and so to stratify risks in insurance and health-care industries. This number has come to be massively consequential in the lives of millions of people, and to influence the movement of billions of dollars.