Branko Milanović grew up in Yugoslavia, during the nineteen-sixties and seventies. He became an economist at the World Bank and then a professor at CUNY; on his blog, Globalinequality, he discusses economics and reminisces about the past. Recently, he published a post about his youth. He had been reading histories of the postwar decades, by Svetlana Alexievich, Tony Judt, and others. Faced with these grim accounts, Milanović felt protective of his past. “However hard I tried,” he wrote, “I just could not see anything in my memories that had to deal with collectivization, killings, political trials, endless bread lines, imprisoned free thinkers,” and so on. Instead, he had mainly good memories—of “long dinners discussing politics,” the “excitement of new books,” “languid sunsets, whole-night concerts, epic soccer games, girls in miniskirts.” He worried that, with the passage of time, it was becoming harder to imagine life under Communism as anything other than a desperate struggle with deprivation and repression. He titled his post “How I Lost My Past.”

Was the past good or bad? Are we on the right track or the wrong one? Is life getting better or worse? These questions are easy to ask—pollsters and politicians love asking them—but surprisingly hard to answer. Most historical and statistical evidence shows that life used to be shorter, sicker, poorer, more dangerous, and less free. Yet many people, like Milanović, have fond memories of bygone years, and wonder if reports of their awfulness have been exaggerated. Others concede that life used to be worse in some ways, but wonder if it wasn’t also better in others—simpler, more predictable, more spiritual. It’s common to appreciate modernity while fearing its destructive potential. (Life expectancy may be higher today, but it will be shorter after the nuclear-climate-bioterror apocalypse.) If being alive now doesn’t feel particularly great, perhaps living in the past might not have felt particularly bad. Maybe human existence in most times and places is a mixed bag.

Last year, the Pew Research Center asked people around the world whether life had been better or worse in their countries fifty years ago. A slim plurality of Americans said they thought life had been better. In 1967, the United States was embroiled in the Vietnam War. Protest marches were taking place around the country, crime was surging, and race riots were breaking out in Detroit, Newark, Milwaukee, and other cities. That spring, a wave of tornadoes injured thousands across the Midwest; members of the Black Panther Party, carrying shotguns and rifles, marched into the California statehouse to protest a racially motivated gun-control law. In June, the Six-Day War broke out. Americans lived in smaller houses, ate worse food, worked more hours, and died, on average, seven years earlier. On the other hand, NASA launched several moon probes and Jimi Hendrix’s “Are You Experienced” helped launch the Summer of Love. By an obscure retrospective calculus, the good appears to balance out the bad. Frightening events seem less so in retrospect. Memory is selective, history is partial, and youth is a golden age. For all these reasons, our intuitive comparisons between the past and the present are unreliable. Many Americans living in 1967 might well have thought that life had been better in 1917.

Nor is this just an American inclination. In “Enlightenment Now: The Case for Reason, Science, Humanism, and Progress,” the cognitive scientist Steven Pinker looks at recent studies and finds that majorities in fourteen countries—Australia, Denmark, Finland, France, Germany, Great Britain, Hong Kong, Malaysia, Norway, Singapore, Sweden, Thailand, the U.A.E., and the United States—believe that the world is getting worse rather than better. (China is the only large country in which a majority expresses optimism.) “This bleak assessment of the state of the world is wrong,” Pinker writes—and not just a little wrong but “wrong wrong, flat-earth wrong.”

Because our ideas about human progress are so vague, it’s tempting to think they don’t matter. But “Is life getting better or worse?” may be a dorm-room debate with consequences. It has affected our politics, Pinker says, encouraging voters to elect unproved leaders “with a dark vision of the current moment.” He quotes from Donald Trump’s Inaugural Address, in which the President bemoaned “mothers and children trapped in poverty . . . an education system which leaves our young and beautiful students deprived of all knowledge . . . and the crime, and the gangs, and the drugs.” In fact, poverty, crime, and drug abuse are declining in America, and our educational system, though flawed, is one of the best in the world. Pessimism can be a self-fulfilling prophecy. By believing that the world is getting worse, Pinker argues, we can make it so.

It’s also possible to take this reasoning to an extreme—to become radically pessimistic about the consequences of pessimism. In “Suicide of the West,” the conservative intellectual Jonah Goldberg argues that progressive activists—deluded by wokeness into the false belief that Western civilization has made the world worse—are systematically dismantling the institutions fundamental to an enlightened society, such as individualism, capitalism, and free speech. (“Sometimes ingratitude is enough to destroy a civilization,” Goldberg writes.) On the left, a parallel attitude holds sway. Progressives fear the stereotypical paranoid conservative—a nativist, arsenal-assembling prepper whose world view has been formed by Fox News, the N.R.A., and “The Walking Dead.” Militant progressives and pre-apocalyptic conservatives have an outsized presence in our imaginations; they are the bogeymen in narratives about our mounting nihilism. We’ve come to fear each other’s fear.

With “Enlightenment Now,” Pinker hopes to return us to reality. In the course of five hundred pages, he presents statistics and charts showing that, despite our dark imaginings, life has been getting better in pretty much every way. Around the globe, improved health care has dramatically reduced infant and maternal mortality, and children are now better fed, better educated, and less abused. Workers make more money, are injured less frequently, and retire earlier. In the United States, fewer people are poor, while elsewhere in the world, and especially in Asia, billions fewer live in extreme poverty, defined as an income of less than a dollar and ninety cents per day. Statistics show that the world is growing less polluted and has more parks and protected wilderness. “Carbon intensity”—the amount of carbon released per dollar of G.D.P.—has also been falling almost everywhere, a sign that we may be capable of addressing our two biggest challenges, poverty and climate change, simultaneously.

Pinker cites statistics showing that, globally, there are now fewer victims of murder, war, rape, and genocide. (In his previous book, “The Better Angels of Our Nature,” he attributed this development to a range of causes, such as democratization, pacifism, and better policing.) Life expectancy has been rising, and—thanks to regulations and design improvements—accidental deaths (car crashes, lightning strikes) are also in steep decline. Despite what we’re often told, students today report being less lonely than in the past, and, although Americans feel overscheduled, studies show that men and women alike have substantially more leisure time than their parents did (ten and six hours more per week, respectively).

“Enlightenment Now” seems designed to reassure both Republicans, who worry about increasing drug use and terrorism, and Democrats, who see racism and sexism as the crises of our time. Despite fears of resurgent racism, the number of hate crimes in America has been falling for decades, while analyses of Internet searches, which reveal searchers’ hidden interests, indicate that racist, sexist, and homophobic attitudes are also in retreat. What Pinker calls “emancipative values”—tolerance, feminism, and so on—are becoming more common even in old-fashioned societies. (Young people in the Middle East now hold social views comparable to the ones held by young Western Europeans in the nineteen-sixties.) Although there’s been a recent surge in drug overdoses in the U.S., most of those who die belong to “the druggy Baby Boomer cohort . . . born between 1953 and 1963.” Drug and alcohol use among teen-agers—with the exception of cannabis and vaping—is at its lowest level since 1976.