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I.

London, 1665. The capital smelled of death in its last large outbreak of the Plague, the worst since the Black Death of the 14th century. The diarist Samuel Pepys mourned, “Every day sadder and sadder news of its increase. In the City died this week 7,496; and of all of them, 6,102 of the Plague. But it is feared that the true number of the dead this week is near 10,000 — partly from the poor that cannot be taken notice of through the greatness of the number.”

As the deaths mounted and the streets filled with waste, Londoners noticed that dogs and cats were everywhere in the city. And so the order went out from the Lord Mayor.

Kill the dogs and cats.

Our new global crises are so challenging because the bads are so tightly bound up with the goods.

The Chamberlain of the City paid the huntsmen, who slaughtered more than 4,000 animals. But the dogs and cats were chasing the rats that were feeding on the waste — and the rats were carrying the fleas that transmitted the Plague. Now spared from their predators, the rats spread the affliction even more fiercely. The medical advice from London’s College of Physicians — to press a hen hard on the swellings until the hen died — did not slow the disease. In the end, the Plague of 1665 is thought to have killed almost 20 percent of London’s population (the equivalent of a million and a half people today). A great fire then consumed a third of the city.

Many humans and animals died in this crisis of ignorance. Now that we understand the Plague bacterium, we know what procedures and medicines will keep the disease from becoming epidemic. Ignorance, we might say, no longer plagues us.

Today, pestilence threatens us not because of our ignorance but because of the success of our systems. Our transportation networks are now so fast and far-flung that they transmit diseases worldwide before cures can catch up. The next epidemics will play on our strengths, not our weaknesses — fighting them will mean canceling flights, not killing fleas. This Horseman of the Apocalypse has dismounted and now travels coach.

The 20th century marked an inflection point — the beginning of humanity’s transition from its ancient crises of ignorance to its modern crises of invention. Our science is now so penetrating, our systems are so robust, that we are mostly endangered by our own creations. Our bomb-making is now informed by particle physics; our computers are becoming ever-better informed about our private lives.

In 1665, half a billion humans sweated to sustain the species near subsistence with their crude implements. Now our global economy is so productive that 16 times that number — some 8 billion humans — will soon be alive, and most will never have known such poverty.

Indeed, our machines have multiplied so much that a new crisis looms because of the smoke coming off them as they combust. Future food crises, if they come, will be driven by anthropogenic climate change. Famine will descend not from the wrath of God but from the growth of gross domestic product. We ourselves are outfitting the Horsemen of the future, or perhaps it’s better to say that we are creating them.

Now in print The Stone Reader: Modern Philosophy in 133 Arguments An anthology of essays from The Times’s philosophy series, published by Liveright.

Our new crises of invention are so challenging because the bads are so tightly bound with the goods. Breaking the world’s slave chains was a moral triumph; breaking the world’s supply chains is not an option. Climate change is a crisis of invention. So many more people, living longer, eating better, traveling more to see the world and one another — is it not poignant that these human goods are engendering a mortal danger?

II.

Molecules are heavy and expensive; bits are fast and cheap. So if the past was about scarcity, the future should be about abundance — but the future may well be abundant with trouble. Whether humans can overcome their coming crises of invention will turn on the philosopher’s old question of whether individuals are essentially good or evil, which is a hard question — but recent news will tempt many thumbs to turn downward.

A more positive answer emerges if we switch to a systems perspective, evaluating humanity as a whole as we would an ecosystem or a complex machine. What happens when humanity “adds” energy to itself — what happens when humanity produces and consumes more energy, as it’s done massively in the transition from wood and muscle power to fossil fuels and alternatives?

The encouraging answer is that with more energy the species grows like crazy. And adding more energy has also activated some potentiality that has made humans generally more tolerant, more cooperative and more peaceful. Humans have, it’s true, developed energy weapons powerful enough to destroy the entire system. Yet so far, they have not used those weapons to do so. So far, at least, more energy = more humanity.

Something is happening to our species, and especially over the last 70 years. The years since 1945 have seen many horrors: the partition of India, China’s Great Leap Forward, the Vietnam War, the Biafran crisis, the Khmer Rouge and the Rwandan genocide, wars in Afghanistan, Iraq and Syria, mass slaughters, civilizational dictatorships, widespread famines and the grueling civil conflicts that have become watchwords for evil in our time. Today our screens overflow with chaos and hate, and today our screens follow us everywhere.

Yet this has also been the most prosperous time in human history by far. And by a long way the time with the greatest increase in democracy around the world. It has also been the most peaceful era in recorded human history. What Hegel called the slaughter-bench of history is becoming less bloody.

Humanity does learn, painfully and often only after thousands or even millions have died.

That thesis about “the most peaceful era in history” is naturally the hardest to believe, yet it’s true. As Joshua Goldstein puts it in “Winning the War on War,” “We have avoided nuclear wars, left behind world war, nearly extinguished interstate war, and reduced civil wars to fewer countries with fewer casualties.” Goldstein continues:

In the first half of the twentieth century, world wars killed tens of millions and left whole continents in ruins. In the second half of that century, during the Cold War, proxy wars killed millions, and the world feared a nuclear war that could have wiped out our species. Now, in the early twenty-first century, the worst wars, such as Iraq, kill hundreds of thousands. We fear terrorist attacks that could destroy a city, but not life on the planet. The fatalities still represent a large number and the impacts of wars are still catastrophic for those caught in them, but overall, war has diminished dramatically.

The percentage of states perpetrating mass killings of civilians is also well down since 1945, and fatalities from armed assaults on civilians (and from genocide) are down since reliable records have been kept. And while the numbers on deaths from terrorism vary according to the definition of that word, all agree that the numbers of terrorism deaths are quite small compared with those caused by (increasingly rare) wars.

These statistics definitely do not prove that animus or madness has ended. No decent person would deny that violence is still much too high everywhere. And there is no guarantee that any of these positive trends will continue.

Still, the big picture of postwar history shows significant improvements in nearly all indicators of lived human experience. The average life span of humans is today longer than it has ever been. A smaller proportion of women die in childbirth than ever before. Child malnutrition is at its lowest level ever, while literacy rates worldwide have never been higher. Most impressive has been the recent reduction in severe poverty — the reduction in the percentage of humans living each day on what a tall Starbucks coffee costs in America. During a recent 20-year stretch the mainstream estimate is that the percentage of the developing world living in such extreme poverty shrank by more than half, from 43 to 21 percent.

The real trick to understanding our world is to see it with both eyes at once. The world now is a thoroughly awful place — compared with what it should be. But not compared with what it was. Keeping both eyes open gives depth to our perception of our own time in history, and makes us better able to see where paths to more progress may be open.

III.

It would be ungenerous to be impatient with humanity, which — like each one of us — needs time to learn. It was quite a shock for humankind to wake one day with atomic weapons suddenly in its midst, especially as a world war was then ablaze. In 1945, humanity had little idea how to handle this novel existential threat. But it learned, through death and nightmares, and at least so far, it has done better than many first feared. With ever more crises of invention emerging, humanity will need to learn again, and it will need to learn quicker and better.

Humanity does learn, painfully and often only after thousands or even millions have died — like a giant starfish hurrying over a jagged reef, with only primitive vision, slicing off spines on its way, yet regenerating as it grows and slowly adapting its motion. The currents are pushing the starfish faster, the reefs ahead are sharper — humanity must become sharper, too. Mainly, humanity learns as identities alter to become less aggressive and more open, so that networks can connect individual capacities more effectively and join our resources together.

Many people are still beyond ruthless in pursuing their own interests, yet interests are now more pacific than they once were. Most people around you now do not want to kill you to get your phone, torture you until you profess their religion, or prey on your credulity until you join a racist gang. Some may — but not many. If these profound changes for the better remain unseen, it is likely because of what we now take for granted.

What we take for granted frames the size of our concerns. We’ve come to expect that mayors and police chiefs will not endorse, much less order, the lynching of minorities. Within that frame, racial profiling and deaths in police custody are top priorities. After decades, we’ve come to expect enduring peace among the great powers. Within that frame any military action by a major power, or a civil war in a resource-rich state, rightly becomes top news.

We can’t relax; the upward trends in time’s graphs may crest at any point. Yet batting away the positive facts is lazy, and requires only a lower form of intelligence. There are immense challenges: climate change, resource scarcity, overpopulation, and more. Still, these are the follow-on problems of species achievement, as the world gets more crowded and productivity grows. These are the burdens of our success. Something is happening — especially since World War II — as we add more energy to our species. What future generations might marvel at most will be if we, in the midst of it, do not see it.

Leif Wenar holds the chair of philosophy and law at King’s College London. He is the author of “Blood Oil: Tyrants, Violence, and the Rules that Run the World,” from which this essay was adapted.

Now in print: “The Stone Reader: Modern Philosophy in 133 Arguments,” An anthology of essays from The Times’s philosophy series, edited by Peter Catapano and Simon Critchley, published by Liveright Books.

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