Human Extinction: A Brief Guided Tour of the Book

200,000 words condensed into 20,000

You can also listen to this article on YouTube at the linke above. A PDF version is on my website here. Follow me on Twitter: @xriskology, and support my work, if you’d like, here.

Introduction

The main text of my new book, Human Extinction: A History of the Science and Ethics of Annihilation, is 457 pages long, or around 200,000 words. That’s a lot to read. So, I thought it might be useful to outline some of the key ideas of Part I and Part II. In brief:

Part I is an intellectual history of thinking about human extinction (mostly) within the Western tradition. When did our forebears first imagine humanity ceasing to exist? Have people always believed that human extinction is a real possibility, or were some convinced that this could never happen? How has our thinking about extinction evolved over time? Why do so many notable figures today believe that the probability of extinction this century is higher than ever before in our 300,000-year history on Earth? Exploring these questions takes us from the ancient Greeks, Persians, and Egyptians, through the 18th-century Enlightenment, past scientific breakthroughs of the 19th century like thermodynamics and evolutionary theory, up to the Atomic Age, the rise of modern environmentalism in the 1970s, and contemporary fears about climate change, global pandemics, and artificial general intelligence (AGI).

Part II is a history of Western thinking about the ethical and evaluative implications of human extinction. Would causing or allowing our extinction be morally right or wrong? Would our extinction be good or bad, better or worse compared to continuing to exist? For what reasons? Under which conditions? Do we have a moral obligation to create future people? Would past “progress” be rendered meaningless if humanity were to die out? Does the fact that we might be unique in the universe—the only “rational” and “moral” creatures—give us extra reason to ensure our survival? I place these questions under the umbrella of Existential Ethics, tracing the development of this field from the early 1700s through Mary Shelley’s 1826 novel The Last Man, the gloomy German pessimists of the latter 19th century, and post-World War II reflections on nuclear “omnicide,” up to current-day thinkers associated with “longtermism” and “antinatalism.”

In the book, I call the first history “History #1” and the second “History #2.” For the most part, History #1 shaped the trajectory of History #2, although I argue that this relationality reversed, in a momentous way, at the turn of the 21st century, when ethical considerations about the extreme “badness” of extinction influenced how a number of quite influential people came to think about our collective existential predicament in the universe.

As you can see in this Google Ngram Viewer graph, the frequency of references to “human extinction” increased after World War II, spiked in the 1980s, and since the 1990s has more or less exponentially risen. One of the central aims of the book is to explain why this is the case.

Both histories are dominated by white men. This is largely due to the fact that the overwhelming majority of people who have written about human extinction have been white men; indeed, there are perhaps only 30 or so Western philosophers—that’s it—who have offered anything close to a systematic analysis of the ethics of extinction. Why it is that privileged white men have dominated Existential Ethics is a question that I hope to address in subsequent papers. The most obvious answer is that an extinction-causing catastrophe would directly affect them, whereas non-extinction catastrophes like global poverty and localized famines, and social injustices like racism and sexism, do not. Worrying about human extinction and occupying a privileged position in society have been intimately connected.

Let’s take a closer look at History #1 and History #2. In order to make sense of History #2, though, we will need to examine a number of theoretical issues. Hence, the following document is divided into three main sections. The first summarizes History #1. The second lays the theoretical groundwork for Existential Ethics. And the third summarizes History #2. I conclude with a short summary of some key ideas. Although I will pass over quite a bit of important detail provided in the book, this will give readers a good overview of the territory that I cover.

Section 1. History #1—Existential Moods

1.1 The Five Existential Moods

Since virtually nothing has been written about the history of thinking about human extinction within the West, I had no obvious point of departure. (The image below shows an early attempt to make sense of this history, from 2019.) So, I voraciously read everything that I thought might be even slightly relevant, hoping to discover some kind of historical patterns.¹ To my surprise, this is exactly what I found: four major shifts in how people within the West have understood our existential predicament in the universe. These shifts are clearly defined, and each unfolded very abruptly. They are sudden revolutions in our thinking about human extinction, each accompanied by figurative and often literal gasps.

I characterize the five periods—separated by four shifts—in terms of the prevailing “existential mood.” This is a type of “public mood,” as in the “mood of the times,” whereby large numbers of people are oriented in the same general direction, toward a particular outlook on humanity’s future—indeed, on whether we will even have a future at all. An existential mood arises from a particular set of answers to fundamental questions about our existential predicament, such as: Is our extinction even possible? One might believe that it is not, perhaps because one thinks that God would never allow it. If it is possible, though, a second question arises: could it actually happen? Perhaps we happen to live in a universe that is completely safe—not on an individual level, of course, but on the level of our species: there just aren’t any ways that humanity itself could disappear. I call a “way that humanity could disappear” a kill mechanism, examples being nuclear war and a global pandemic. Additional questions include: if there are kill mechanisms stalking humanity, how many? Are they natural or anthropogenic? How likely is it that a kill mechanism catapults us into the collective grave? Is this probability rising or falling? Could extinction happen in the near term? Is our extinction inevitable in the long run? And so on.

Hence, an existential mood is defined by how credible figures at some point in time answered these questions. As noted above, the shift from one set of answers to another has in every case been extremely rapid, while the answers given between each shift in mood have been remarkably stable, with very little change. That said, although the shifts in existential mood were abrupt, it is useful to distinguish between when a mood first emerged and when it fully solidified. The five existential moods are:

(1) The ubiquitous assumption that humanity is fundamentally indestructible. This mood dominated from ancient times until the mid-19th century. Throughout most of Western history, nearly everyone would have said that human extinction is impossible, in principle. It just isn’t something that could happen. The result was a reassuring sense of “Comfort” and “perfect security” about humanity’s future, to quote two notable figures writing toward the end of this period. Even if a global catastrophe were to befall our planet, humanity’s survival is ultimately guaranteed by the loving God who created us or the impersonal cosmic order that governs the universe.

(2) The startling realization that our extinction is not only possible in principle but inevitable in the long run—a double trauma that left many wallowing in a state of “unyielding despair,” as the philosopher Bertrand Russell wrote in 1903. The heart of this mood was a dual sense of existential vulnerability and cosmic doom: not only are we susceptible to going extinct just like every other species, but the fundamental laws of physics imply that we cannot escape this fate in the coming millions of years. This disheartening mood reverberated for roughly a century, from the 1850s up to the mid-20th century.

(3) The shocking recognition that humanity had created the means to destroy itself quite literally tomorrow. The essence of this mood, which percolated throughout Western societies in the postwar era, was a sense of impending self-annihilation. Throughout the previous mood, almost no one fretted about humanity going extinct anytime soon. Once this new mood descended, fears that we could disappear in the near future became widespread—in newspaper articles, films, scientific declarations, and bestselling books. Some people even chose not to have children because they believed that the end could be near. This mood emerged in 1945 but didn’t solidify until the mid-1950s, when one event in particular led a large number of leading intellectuals to believe that total self-annihilation had become a real possibility in the near term.

(4) The surprising realization that natural phenomena could obliterate humanity in the near term, without much or any prior warning. From at least the 1850s up to the beginning of this mood, scientists almost universally agreed that we live on a very safe planet in a very safe universe—not on an individual level, once again, but on the level of our species. Though humanity might destroy itself, the natural world poses no serious threats to our collective existence, at least not for many millions of years, due to the Second Law of thermodynamics. Nature is on our side. This belief was demolished when scientists realized that, in fact, the natural world is an obstacle course of death traps that will sooner or later try to hurtle us into the eternal grave. Hence, the essence of this mood was a disquieting sense that we are not, in fact, safe.

(5) The most recent existential mood—our current mood—is marked by a disturbing suspicion that however perilous the 20th century was, the 21st century will be even more so. Thanks to climate change, biodiversity loss, the sixth major mass extinction event, and emerging technologies, the worst is yet to come. Evidence of this mood is everywhere: in news headlines declaring that artificial general intelligence (AGI) could annihilate humanity, and the apocalyptic rhetoric of environmentalists. As we will discuss more below, surveys of the public show that a majority or near-majority of people in countries like the US believe that extinction this century is quite probable, while many leading intellectuals have expressed the same dire outlook. The threat environment is overflowing with risks, and it appears to be growing more perilous by the year. Can we survive the mess that we’ve created?

A close examination of the historical record, I argue, reveals these five existential moods. I consider this to be a discovery rather than invention: Western history really does consist of five distinct periods, each corresponding to a different set of answers about fundamental questions concerning our existential predicament. The more I looked into this, searching for disconfirming evidence, the more incontrovertible the periodization became.

I should add a nuance about the first existential mood: there were some early thinkers who envisioned humanity dying out, such as the ancient Greek philosophers Xenophanes, Empedocles, and the Stoics. All believed not just that our extinction is possible, but that it is unavoidable. However, they also believed that, after disappearing entirely, humanity would always reappear. In Xenophanes’ account, the cosmos cycles through two stages: wetness and dryness. During the stage of wetness, all life vanishes, though it returns during the stage of dryness; this happens over and over again for eternity. Using terminology that I introduce later on in the book, Xenophanes and the other ancient philosophers believed that we would undergo “demographic extinction” (we disappear entirely) but not “terminal extinction” (we disappear entirely and forever). The view that humanity is indestructible is thus compatible with belief in our extinction.²

Hence, the notion of human extinction dates back to the ancient world, even though the very same individuals who posited “demographic” extinction as a future inevitability also accepted our indestructibility in a broader cosmic sense. Yet this idea that we are fundamentally indestructible took on a much more radical form with the rise of Christianity, which saw our extinction in even the most minimal sense as impossible. Indeed, Christians would have argued that the concept of human extinction is quite literally unintelligible, incoherent, or self-contradictory, not unlike the concepts of married bachelor and circles with corners, for reasons discussed below. Historically speaking, Christianity became widespread in the Roman Empire around the 4th or 5th centuries CE, and maintained a stranglehold on the Western worldview until the 19th century, when it declined significantly among the intelligentsia. It was this century that Friedrich Nietzsche famously declared that “God is dead” and Karl Marx described religion as the “opium of the masses.” The 19th century is when atheism became popular among the educated classes, though it wasn’t until the 1960s that, to borrow a phrase from the theologian Gerhard Ebeling, the “Age of Atheism” commenced and a secular outlook spread throughout society more generally.

1.2 Enabling Conditions

The periodization above is a story of psycho-cultural trauma—of realizing that we are not a permanent feature of the universe, and in fact nature or humanity itself could nudge us over the precipice of extinction in the very near future, maybe within our own lifetimes. But what explains this periodization? Why did these shifts occur? Why did they occur when they did, rather than some other time? How did this all happen?

This is where I introduce an explanatory hypothesis, which I argue could also be used to predict how the idea of human extinction might evolve in the future. It consists of two parts: enabling conditions and triggering factors. Let’s consider these in turn:

As the term “enabling conditions” suggests, this refers to conditions that enabled the idea of human extinction to no longer be an unintelligible impossibility to many people in the West. Since Christianity is what rendered human extinction an unintelligible impossibility after its rise in the 4th or 5th centuries CE, it was the secularization of Western civilization—i.e., the decline of Christianity—that made human extinction look like a real possibility. In particular, it was the dissolution of two clusters of beliefs, both central to the Christian worldview for roughly 1,500 years, that opened up the conceptual space needed to see our extinction as something that could, at least in principle, happen.

The first cluster is the Great Chain of Being. I call this a “cluster” because it consists of three component ideas: the principle of plenitude, principle of continuity, and principle of unilinear gradation, which we needn’t go into detail about here. The Great Chain is a model of reality according to which everything that exists can be ordered into a linear hierarchy: God is at the top, followed by angelic beings, humans, animals, zoophytes (transitional species), plants, and minerals at the bottom. Crucially, the model assumed that it is impossible for any links in the chain to go missing, even temporarily. This might sound strange to contemporary ears, but the Great Chain was hugely influential for a millennium and a half. Its influence was absolutely pervasive, as Arthur Lovejoy explores in his magisterial book The Great Chain of Being (1936). Since the extinction of anything is fundamentally impossible, the Great Chain implies that our own extinction is impossible, too. Hence, this first cluster of beliefs made a general point about extinction.

The second cluster consists of what I call the ontological and eschatological theses. These make a specific point about humanity, and hence if one accepts them, one will believe that our own extinction is impossible even if one believes that the extinction of other species can happen. The ontological thesis states that humanity is immortal, because each member of humanity is immortal. We are immortal because, according to standard Christian anthropology, we consist of an immortal soul that, once created, will never cease to exist. This explains why the idea of human extinction would have seemed incoherent or self-contradictory to believers. To say that “humanity can go extinct” would be to say that “an immortal type of thing can undergo a process that only mortal kinds of things can undergo,” which is an obvious logical contradiction. As I write in a footnote, “immortal human” is a pleonasm whereas “human extinction” is a contradiction.

The eschatological thesis states that humanity cannot go extinct because our extinction, in a naturalistic sense, isn’t part of God’s grand plan for humanity and the cosmos. Eschatology is the “study of last things,” and a key aspect of Christian eschatology is balancing the scales of cosmic justice when the world ends. In our world, the wicked are often rewarded, while the righteous sometimes finish last. That is unjust. At the end of time, though, God will rectify this problem. But how can the scales of cosmic justice be balanced if humanity were to cease existing entirely? The show cannot go on without us, and since the show must go on, we cannot go extinct. Human extinction just isn’t on the cards for us; it isn’t how our story ends.

That’s not to say that Christians don’t anticipate an “end to the world.” On the Christian view, however, the world’s end coincides with the beginning of eternity, which contrasts with the idea that extinction would entail our complete and permanent non-existence. Roughly speaking, Christians anticipate a future transformation, while human extinction constitutes our termination.

It was these two clusters of beliefs that rendered human extinction an unintelligible impossibility for roughly 1,500 years. Our extinction, in other words, would have been simply unthinkable. In the very early 19th century, a brilliant French anatomist named Georges Cuvier dealt a mortal blow to the Great Chain: he proved that some species have in fact gone extinct. This was a revolutionary idea that exploded the Great Chain model of reality.³ The eschatological thesis was weakened the previous century, during the Enlightenment, because of the rise of deism. Generally speaking, deists do not accept special revelation—the “truths” supposedly delivered by supernatural deities, such as God or angels, to prophets like John of Patmos, who supposedly wrote the Book of Revelation. Consequently, many Enlightenment deists did not accept the eschatological (end-times) narrative of Christianity. Nonetheless, the influence of the eschatological thesis declined most resolutely with the general fall of Christianity throughout the 19th century, at least among the intelligentsia. This is also when the ontological thesis became untenable, due partly to the theory of evolution proposed by Charles Darwin in his 1859 book On the Origin of Species. Although Darwin avoided the topic of human evolution in his book, the theory he put forward clearly implies that Homo sapiens, our species, evolved in a gradualistic manner from various “lesser” forms. It was difficult to square this with the idea that we are ontologically unique compared to all other creatures, because we have immortal souls and they don’t. If we are different from the rest of life in degree rather than kind, there is no more reason to believe that we are immortal than to believe that chimpanzees are.

Note that the eschatological thesis and, especially, the ontological thesis persisted after the Great Chain collapsed. Hence, it was still widely believed that humanity could not go extinct, even if other species can. The decline of these two theses is what finally enabled human extinction to become an intelligible possibility. This was a shocking realization.

1.3 Triggering Factors

This brings us to “triggering factors.” Consider this: have you ever worried about walking past an outlet in the wall and being shocked by a bolt of electricity leaping out from it? What about a car that’s currently on the other side of the country running you over on the sidewalk right now? We don’t worry about such things because we know they cannot happen: it just isn’t the way our world works. If there isn’t good reason to believe that something could actually happen, we probably don’t give it much thought. The same goes for extinction. Even if this is possible in principle, if there are no actual kill mechanisms—means of elimination—lurking in the shadows, there may be no particular reason to think much about human extinction. Hence, the discovery of kill mechanisms played an integral role in shaping History #1. In many cases, this is what triggered shifts to new existential moods, which is why I call them “triggering factors.”

Although Western history is full of speculations about global-scale catastrophes, dating back at least to the mid-17th century BCE with the epic poem of Atrahasis, it wasn’t until the 1850s that the first scientifically credible kill mechanism was identified. This was the Second Law of thermodynamics, which states that the entropy (basically, disorder) of an isolated system will tend toward a maximum. Physicists, followed by everyone else, immediately recognized the dismal implications of this: Earth will become increasingly inhospitable to life, until no life at all is possible. Our days are numbered, even if we were to somehow escape Earth: the universe as a whole will ultimately sink into a frozen pond of eternal lifelessness—a state of thermodynamic equilibrium called the “heat death.”⁴ Since there is no escaping the dictatorship of entropy, many came to despair that human existence may be meaningless. What does anything matter if, in the end, all will be lost?

It is remarkable to see that, prior to the 1850s, almost no one fretted about or even considered the possibility of human extinction. After this decade, anxieties about the long-term fate of humanity in an atheistic universe governed by the Second Law were common.⁵ This is what catalyzed the first, abrupt, traumatic shift in existential mood. Before this shift, questions like “Is our extinction possible?,” “Could our extinction actually happen?,” and “Is our extinction inevitable” were all answered with “no.” Not long after, most educated secular people answered them in the affirmative. Hence, it was the decline of Christianity in the 19th century along with the discovery of the Second Law that, together, introduced a new existential mood, which descended on the West with a heavy, heart-wrenching thump.⁶

Since human extinction was no longer seen by everyone as impossible, this period also witnessed a flurry of novel speculations about how we might die out. Some suggested a planetary conflagration, sunspots that blot out the sun, cometary impacts, global pandemics, large boilers (high-tech of the day) that obliterate Earth by exploding, and even evolutionary forces causing humanity to “degenerate” into one or more lesser species, as explored by H. G. Wells’ 1895 novel The Time Machine. Especially after World War I, with its horrors of tanks, poison gas, and flamethrowers, many feared that technological advancements could yield terrible new weapons that kill everyone on the planet. Yet none of these proposed kill mechanisms was widely accepted at the time. The only kill mechanism that scientists agreed on was the Second Law of thermodynamics.

As alluded to above, this changed with the invention of nuclear weapons in 1945. Surprisingly, the atomic bombings of Hiroshima and Nagasaki did not lead to widespread discussions of anthropogenic extinction, although many media outlets reported on these attacks using rather apocalyptic language. But virtually no one linked atomic bombs with human extinction. The focus was instead on the possibility of civilizational destruction, with atomic bombs being seen as (much) bigger hammers that states could use to smash each other to bits. This is captured by a line from a US lieutenant that, if World War III is fought using nuclear weapons, the war after that one will be fought “using spears,” which is often attributed to Einstein, who may have read the news article containing the original statement. In other words, the worry wasn’t that we will annihilate ourselves, but that atomic bombs could slingshot humanity back into the Paleolithic.

It wasn’t until 1954 that people began to explicitly worry about our extinction, and indeed the shift in language from before and after this year is astounding. What happened in 1954? This is when the US tested a thermonuclear weapon—a “hydrogen” rather than “atomic” bomb—in the Marshall Islands of the Pacific, which produced an explosive yield 2.5 times larger than expected. Thermonuclear weapons are much more powerful than atomic weapons, and this event—the Castle Bravo test—catapulted large quantities of radioactive particles into the atmosphere. The result was an international incident with Japan, as a number of Japanese fishermen came down with radiation sickness. More important for our story is that the particles from the Castle Bravo test were detected around the world. Suddenly, it became terrifyingly obvious that even a small-scale thermonuclear conflict between the US and the Soviet Union could blanket our globe with lethal amounts of radioactivity. Radio addresses listened to by millions of people warned that self-annihilation is now a real possibility, and statements signed by world-renowned physicists, including Einstein, declared that a war between the US and Soviet Union could turn Earth into a radioactive hellscape that no human could endure. This was the second credible kill mechanism—global thermonuclear fallout—and it’s what triggered the shift to a horrifying new existential mood, marked by a sense of impending self-annihilation.

Yet this was just one of several kill mechanisms proposed during the postwar era. In 1962, the marine biologist Rachel Carson argued that synthetic chemicals released into the environment could have mutagenic effects, degrading our germ plasm—the genetic material passed down to all future generations—and potentially ending humanity. Others warned about overpopulation and ozone depletion, followed by the discovery of a new type of kill mechanism associated with nuclear weapons: the nuclear winter scenario. Still others, channeling the general anxieties of the time, speculated about genetically engineered pathogens, artificial intelligence systems that self-improve until they are far “smarter” than humans, and even advanced nanotechnology that could convert the biosphere into what one theorist called “gray goo.” Over the course of just a few decades, people went from believing that the only actual kill mechanism was the Second Law to believing that we face a multiplicity of near-term threats to our collective survival. Whereas the Second Law wasn’t scheduled to end humanity for many millions of years, thermonuclear war, environmental degradation, and other such human-caused threats could bring this about on timescales relevant to contemporary people. This was a very frightening transition to a new, darker, more menacing world.

Yet for almost the entire Cold War era, virtually no scientists believed that nature itself—aside from the Second Law—poses any real threats to our existence. This was because of a paradigm in the Earth sciences called uniformitarianism, which essentially states that sudden, catastrophic events can occur on the local level (we know this, of course, because we witness volcanoes, tornadoes, floods, and the like), but never on a planetary scale. Global catastrophes just don’t happen, even if some people, in earlier times, had speculated about things like cometary impacts. This just isn’t the way our universe is. Uniformitarianism became influential in the 1830s, and by the 1850s was widely accepted. It maintained a stranglehold on the Earth sciences until the 1980s and early 1990s, when a series of revolutionary discoveries caused its spectacular implosion.

It all started in 1980, when a team of scientists proposed that the dinosaurs died out 66 million years ago because a giant asteroid struck Earth. Throughout the 1980s, this was hotly debated, with most paleontologists rejecting the idea. Of note is that the hypothesis lacked a smoking gun: if a massive impactor hit Earth, it should have left behind a huge crater. But where is this crater? No one had a clue—that is, until a graduate student discovered the Chicxulub crater buried underground, beneath the Yucatan Peninsula. This discovery was published in 1991, and over the course of just a few months, virtually the entire scientific community came to the shocking realization that uniformitarianism is wrong and global catastrophes caused by natural phenomena can happen. The ominous implications of this were immediately recognized: if global catastrophes have happened in the past, they can happen again in the future. We are not, in fact, living on a very safe planet in a very safe universe. At some point in the future, nature is going to try to commit filicide—the killing of one’s children.

This bombshell triggered yet another shift in existential mood, corresponding to a different set of answers to the questions mentioned earlier. The threat environment was getting more and more crowded, not just by anthropogenic risks but by natural dangers as well. Indeed, once Earth scientists were extricated from the uniformitarian paradigm, they began to speculate about other natural risks, such as volcanic supereruptions, which some linked to a near-extinction event for humanity some 75,000 years ago, after a supereruption in Indonesia spewed huge quantities of sulfate aerosols into the stratosphere, blocking out the sun for many years. It turns out that nature is an obstacle course of existential hazards—not just threats from above, like asteroids and comets, but risks from below, associated with geophysical phenomena on our terrestrial home.

Our most recent existential mood emerged in the late 1990s and early 2000s. The shift to this mood was a little bit different than previous shifts, because it wasn’t triggered by the discovery of any new kill mechanisms. Rather, it resulted from two important developments that unfolded in parallel. The first is rather complicated. In the 1980s and 1990s, a number of philosophers began to think seriously about the ethical implications of our extinction. They concluded that human extinction would constitute a moral tragedy of quite literally cosmic proportions, not so much because a catastrophe that wipes out Homo sapiens tomorrow would kill billions of people on Earth, but because no longer existing would prevent humanity from realizing vast amounts of “value” in the future.⁷ This means that avoiding extinction is really, really important. But how can we avoid our extinction? The obvious answer is to neutralize all the known threats to our survival: nuclear war, asteroidal assassins, volcanic supereruptions, and so on. What if there are risks that we don’t yet know about? What if something leaps out from the shadows of our collective ignorance and buries us alive, before we even know what’s happened?

These questions launched a number of philosophers on a mission to catalogue every possible risk to our survival, however speculative, hypothetical, improbable, or exotic. This includes dangers that don’t currently exist but might later on this century, a shift toward thinking about potential 21st-century risks that I call the “futurological pivot.” By mapping out the entire threat environment, stretched across the diachronic dimension of time, we will optimally position ourselves to neutralize all these risks, thereby ensuring our safe passage through the obstacle course ahead.

This was the first triggering factor: ethical considerations, associated with History #2, spurred a radical remapping of the threat environment, foregrounding what the futurist Ray Kurzweil called in 1999 “clear and future dangers.” Once an exhaustive list of all the present, emerging, and anticipated future threats was compiled, it became apparent that the 21st century will be far more perilous than the 20th century, due largely to “GNR” technologies, where “GNR” stands for “genetics, nanotech, and robotics,” the last of which includes artificial intelligence. What lies ahead should make us shudder, though many of the same figures who became anxious about the future—I call them “riskologists”—also believed that if advanced technologies do not destroy us, they will usher in a techno-utopian world of endless abundance, immortality, and unfathomable pleasure.

The second triggering factor arose from new research on anthropogenic climate change, biodiversity loss, and the sixth mass extinction, which showed that these are far more catastrophic than previously understood. It might be surprising to know that it wasn’t really until the 2000s that climatologists and environmentalists saw such threats as dire. Some climate scientists had, of course, warned about carbon dioxide altering Earth’s thermostat decades earlier—and it would have been wise to listen to them. But as the historian Spencer Weart notes, the “discovery” of global warming wasn’t “complete” until the very early 2000s, at which point scientific debate about the matter effectively ceased. Since then, the overwhelming consensus has been that climate change is real and anthropogenic, and the window for meaningful action to prevent a climate catastrophe is rapidly closing. Along similar lines, it wasn’t until the year 2000 that the concept of the “Anthropocene” was added to our shared lexicon of ideas. While climate change and the Anthropocene loom large in the environmental movement today, they were largely or entirely off the radar of environmentalists throughout the 20th century.

Together, these two developments paint a dismal picture of the future. The dangers are enormous and almost certainly growing, as the climate crisis worsens and the march of scientific and technological “progress” accelerates. This is our current existential mood: the worst is yet to come. Evidence of this mood is everywhere, as noted above: one recent survey found that roughly 40% of Americans believe that climate change will cause our extinction. Another reports that 54% of people in the US, UK, Canada, and Australia rate “the risk of our way of life ending within the next 100 years at 50% or greater.” Earlier this year, a survey from Monmouth found that 55% of Americans are “very” or “somewhat worried” that advanced artificial intelligence will annihilate us.

Many prominent scholars agree with the public. Noam Chomsky declared in 2016 that the risk of human extinction is “unprecedented in the history of Homo sapiens,” while Stephen Hawking warned the same year that “we are at the most dangerous moment in the development of humanity.” Even pro-technology TESCREALists like Nick Bostrom put the probability of extinction before 2100 at 20%. The direness of our existential predicament is perhaps best encapsulated by the Doomsday Clock, which is currently set to 90 seconds before midnight, which represents doom. By comparison, the closest the Doomsday Clock came to midnight during the Cold War was in 1953, after the US detonated the first thermonuclear weapon. That year, the minute hand was placed at a “mere” 2 minutes before doom. According to the Doomsday Clock, our current situation is more perilous than anytime during the 20th century. And there is every reason to believe that the minute hand will inch forward in the years to come.

1.4 Existential Hermeneutics

The backdrop to the most recent shifts in existential mood has been, of course, the enabling condition of secularization. Without a secular worldview, few people would believe that human extinction, in a naturalistic sense, is even possible. This points to another important idea in Part I of the book, which I call an “existential hermeneutics.” By this I just mean a lens through which to interpret the dangers surrounding us. The key idea is that the threat environment isn’t a given—the world must be interpreted, and it’s this interpretation that yields the threat environment. Existential hermeneutics are lenses through which to interpret dangers, and they can be religious or secular to varying degrees. Two people with radically different hermeneutics might look at the very same dangers and come to opposite conclusions about the riskiness or significance of those dangers—about whether to be frightened or not. Put differently, how one maps the threat environment depends on two things: first, a particular model of the world, which may be more or less empirically accurate. And second, the hermeneutical lens through which this model is filtered, thus yielding the threat environment. The threat environment, as one sees it, can therefore change if either of these two variables is altered.

Consider the case of nuclear weapons. While secularization in the West accelerated greatly during the 1960s, there were still plenty of people in the latter 20th century who embraced the ontological and eschatological theses. They believed that humanity is immortal, and that we play an integral role in God’s grand plan for the cosmos. Consequently, they did not believe that thermonuclear war could cause our extinction, and hence were not worried about this outcome. Instead, they integrated the new threat of nukes into the end-times narrative of the Bible. As I write in the book, end-times prophesies are both rigid and highly elastic, often able to accommodate unforeseen developments as if the Bible predicted them all along. Ronald Reagan provides an example. In 1971, while he was governor of California, he declared that,

for the first time ever, everything is in place for the battle of Armageddon and the Second Coming of Christ. … It can’t be long now. Ezekiel [38:22] says that fire and brimstone will be rained upon the enemies of God’s people. That must mean that they’ll be destroyed by nuclear weapons. They exist now, and they never did in the past.

For Reagan and other evangelicals, the possibility of a nuclear holocaust was filtered through the lens of a religious hermeneutics. Consequently, their mapping of the threat environment was completely different than the mapping of atheists like Carl Sagan and Bertrand Russell. The latter two did not see nuclear weapons as part of God’s grand plan to defeat evil. Rather, a thermonuclear Armageddon would simply be the last, pitiful paragraph of our species’ autobiography. Whereas for Christians, the other side of the apocalypse is paradise, for atheistic individuals it is nothing but oblivion. In this way, secularization played an integral part in enabling the discovery and creation of new kill mechanisms to alter the threat environment and, with these alterations, to induce shifts from one existential mood to another.

1.5 Looking Forward to the Future

I claimed above that the combination of enabling conditions and triggering factors yields not just an explanation of the five existential moods, but could also allow us to make predictions about how our thinking about human extinction might evolve in the future. I’ll give two quick examples to illustrate the predictive component of this hypothesis.

First, is there any reason to believe that we’ve discovered or created every possible kill mechanism? Just four decades ago, nearly all scientists believed that asteroids and volcanoes cannot cause global catastrophes. What other natural phenomena, deadly dangers lurking in the cosmic shadows, might haunt us? What might we discover in the future? Alternatively, what new technologies might we create that could pose unprecedented threats to our collective survival? Just as Charles Darwin’s mind would have been boggled by the thought of nuclear weapons and genetic engineering, perhaps there are inventions that we cannot now even begin to anticipate. If there are new kill mechanisms discovered or created in the future, these could initiate yet another shift in existential mood. We should anticipate this possibility with a high degree of trepidation.

Second, is there any reason to assume that the trends of secularization will continue in the future? History is full of religious revivals. Although these trends appear robust—one study even argues that religion is racing toward “extinction” (their word) in nine Western countries—it’s not impossible that they reverse. If that were to happen, we could return to the first existential mood, with many people coming to believe that humanity is, in fact, fundamentally indestructible. For atheists, this might be quite frightening, since a world run by extinction denialists that is simultaneously full of catastrophically dangerous technologies looks like a highly combustible situation. It could even hasten a global disaster, as religious extremists take it upon themselves to use these technologies to bring about the apocalypse. During the Cold War, some evangelical Christians argued that the US shouldn’t try to make peace with the Soviet Union, since a nuclear Armageddon with the “Evil Empire” is all part of God’s plan for the world. As the televangelist Jim Robins said during the 1984 Republican National Convention: “There’ll be no peace until Jesus comes. Any preaching of peace prior to this return is heresy; it’s against the word of God.” Similarly, when Reagan’s Secretary of the Interior, James Watt, was asked about “preserving natural resources for future generations,” he dismissively responded: “I do not know how many future generations we can count on before the Lord returns.”

Not all religious people hold such extreme beliefs, of course. Many religions have a very good track record with respect to, say, taking climate change seriously. And, of course, one need not believe that human extinction is possible to worry about global-scale catastrophes from climate change, pandemics, and artificial intelligence. The point is that if Christianity reemerges in the West, there will likely be some who adopt radical views. If the past is any indication, these people could rise to the highest levels of political power, which may be disconcerting.

In sum, there have been five distinct existential moods in Western history. All four shifts in mood were enabled by the decline of Christianity, which continues up to the present. The first three of these shifts were triggered by the discovery of new kill mechanisms, while the forth was triggered by a combination of ethical considerations and novel research in the environmental sciences. One can think of these existential moods as a palimpsest, with each mood layered on top of previous ones, the only exception being the first mood, which was replaced by the second. Our current existential mood is marked by a fairly pervasive sense that the worst is yet to come, due largely to the dangers associated with emerging technologies and the catastrophic failure of our political leaders to address the environmental crisis.

Section 2. Existential Ethics—The Basics

[Content Warning: The next two sections contain a reference to suicide.]

2.1 Types of Human Extinction

Questions about whether our extinction is possible, how it could happen, what its probability is, and so on, are distinct from questions about whether it would be right or wrong to bring about (ethical questions) and whether it would be good or bad, better or worse if it were to happen (evaluative questions). I call the study of these ethical and evaluative questions “Existential Ethics.” Part II of the book traces the historical development of Existential Ethics from its birth in the 19th century up to the present.

However, to understand this history, it is necessary to disambiguate some terms and sketch the general topography of positions that one could accept within Existential Ethics. The most important term to disambiguate is “human extinction.” It may seem odd that I wait until Part II to address this issue. I do so because, first of all, understanding the different definitions of “human extinction” is rather complicated, and Part I is convoluted enough as it is. Second, the primary subject of History #1 is “human extinction” in what I call the prototypical sense, which is the most intuitive conception of extinction. This means that it wasn’t, strictly speaking, necessary to delve into such detail. I’ll say more about the prototypical conception in a moment. Third, distinguishing between different types of human extinction is a prerequisite for making sense of Existential Ethics. Many ethical theories about our extinction don’t just concern the prototypical sense, but other types of human extinction as well. This is why disambiguating the term is crucial for Part II of the book.

2.2 What Is Humanity?

The term “human extinction” is ambiguous because both “human” and “extinction” are ambiguous. The most obvious definition of “human” equates it with Homo sapiens, our species. Yet if you were to ask an anthropologist, they would say that “human” means our genus Homo, which includes a range of species from Homo habilis, the very first humans, to Homo erectus, Homo heidelbergensis, Homo neanderthalensis (Neanderthals), and Homo sapiens, the only surviving human species today.

Whereas this provides a backward-looking perspective, there are also future-looking definitions, which are especially relevant to Existential Ethics. The futurist Jason Matheny uses “‘humanity’ and ‘humans’ to mean our species and/or its descendants.” I take this to encompass all populations of future beings that are genealogically or causally related to us. Another futurist writes that “by ‘humanity’ and ‘our descendants’ I don’t just mean the species [Homo] sapiens. I mean to include any valuable successors we might have,” later describing these as “sentient beings that matter.” This adds a normative dimension to the definition: it’s not just future beings that are genealogically or causally related to us, but beings that are valuable or matter in a moral sense. If they don’t matter in this sense, they won’t count as “human.”

Along similar lines, the longtermists Hilary Greaves and William MacAskill stipulate that “human” refers “both to Homo sapiens and to whatever descendants with at least comparable moral status we may have, even if those descendants are a different species, and even if they are non-biological.” In other words, future beings that are genealogically or causally related to us—our descendants—will count as human only if they possess a certain moral status. The most capacious definition comes from the neo-eugenicist Nick Bostrom, who defines “humanity” as “Earth-originating intelligent life.” This would include “intelligent” creatures that might evolve entirely separate from us, on a completely different lineage. If Homo sapiens were to die out tomorrow but these beings were to emerge 1 million years from now, then “human extinction” wouldn’t have happened.

It is worth noting that we do not yet have good terminology for these ideas. Consider that Bostrom and others would classify radically “enhanced” future people as “posthumans.” Yet on most of the definitions given above, these posthumans could also count as “humans.” Hence, the same being could be both posthuman and human, which is obviously confusing. I explore this problem in the book, but do not propose any new terms to clarify the issue.

In what follows, I will assume as a default that “human” means Homo sapiens, deviating from this definition when necessary.

2.3 What Is Extinction?

These are a few ways that “human” or “humanity” can be defined. But what about “extinction”? If you ask an evolutionary biologist, they’ll say that there are many different kinds of extinction that species can undergo: demographic, phyletic, functional, ecological, and so on. Some of these are relevant to the case of humanity, although I believe there are other extinction types that are unique to us. In the book, I argue that there are six distinct human extinction scenarios that are ethically, evaluatively, and historically important. All of these build upon a “minimal definition” of extinction, which is pretty straightforward:

Minimal Definition: Something S has gone extinct if and only if there were instances of S at some point in time, but at some later point in time, this is no longer the case.

This is meant to be a general definition, which could apply no less to cultures and languages than to biological species. With respect to humanity, the minimal definition could be satisfied in at least the following six ways:

(1) Demographic extinction: the population of Homo sapiens dwindles to zero, thus disappearing entirely. This could happen suddenly or gradually, as the image below illustrates. Theoretically, demographic extinction could occur almost instantaneously, if a high-powered particle accelerator were to “nucleate” a vacuum bubble. This bubble would expand in all directions at close to the speed of light, destroying everything in its path. Most extinction-causing catastrophes, though, would unfold over years or decades, as in the case of thermonuclear war and global pandemics. There could also be infertility scenarios that cause the human population to drop over centuries, until no one is left.

(2) Phyletic extinction: this would occur if our species disappears entirely because it evolves into one or more “posthuman” species. One way this could happen is through cyborgization, whereby we integrate technology into our bodies, reengineering ourselves in the process. The result could be a new species of posthuman cyborgs. Or we might replace our biological substrate entirely with something artificial, as would happen if we “uploaded” our minds to computers. If either scenario were to obtain and Homo sapiens were to disappear, we would have undergone phyletic extinction. However, even if we choose not to reengineer ourselves, natural evolutionary mechanisms like natural selection, genetic drift, random mutation, and recombination will eventually shape us into a new species, though this will take tens or hundreds of thousands of years.

(3) Terminal extinction: this would happen if Homo sapiens were to disappear entirely and forever, which could occur as a result of either demographic or phyletic extinction. The crucial idea behind terminal extinction is that it adds a condition of permanence: never again are there any instances of our kind in the universe. Why is this distinction important? There are many reasons. I’ll give two: first, it’s necessary to make sense of past thinking about human extinction. Recall from earlier that Xenophanes posited a theory in which humanity disappears for one stage of the cosmic cycle, but this is only ever a temporary state of affairs. Hence, according to Xenophanes, we will someday become demographically extinct, but we will never become terminally extinct. In fact, we have undergone demographic extinction an infinite number of times in the past, and will undergo this an infinite number of times in the future. Humanity always reappears, though.

Another example is futurological rather than historical: some scholars have argued that technologically advanced civilizations choose to “aestivate,” which refers to a state of dormancy during a warm period. (Hence, some animals aestivate in the summer, while others hibernate in the winter.) Because the universe will be cooler in the future, in accordance with the Second Law, computational costs will be lower. If a civilization values computation, it may decide to become dormant. One way of becoming dormant would be to intentionally cause its own demographic extinction, so long as there was some way of reviving the civilization later on, thereby avoiding terminal extinction. The distinction between demographic and terminal extinction could thus become very important to our own civilization in the future, depending on what it values.⁸ Which brings us to:

(4) Final extinction: this would happen if Homo sapiens were to disappear entirely and forever without leaving behind any successors. What motivates this category is the idea that what happens after we disappear could make a huge difference to how one assesses our disappearance. If Homo sapiens disappears but we leave behind a population of intelligent machines that carry on our civilization, scientific projects, and “values,” some would not see this as bad. Many futurists have argued that we should want this to happen. On their view, terminal extinction might very well be desirable, so long as we avoid final extinction. Others would say that terminal extinction might be bad, but it would be much less bad if it didn’t coincide with final extinction, meaning that having successors would mitigate the badness of our species no longer existing.

Notice that, while final extinction assumes terminal extinction, it is incompatible with phyletic extinction, since becoming phyletically extinct would entail that we have had successors. Also note that I used the phrase “genealogically or causally related to us” earlier to make room for the scenario above, in which we create successors that aren’t clearly part of our evolutionary lineage itself, such as intelligent machines. If we were to evolve through cyborgization or natural selection into a new posthuman species, then we would be genealogically related to these future beings. But if we were to create an entirely new lineage, we wouldn’t be related to them in this way, although the entities in this new lineage would be causally connected to us, by virtue of us having created them. By using the phrase “genealogically or causally,” I’m leaving open the possibility that our descendants belong to a distinct lineage, one that we bring into existence.

(5) Normative extinction: this would happen if we have successors, but these beings were to lack something—a capacity, attribute, or property—that is normatively necessary for them to count as “human.” This is where the normative definitions of “human” and “humanity” become very important. Imagine a scenario in which we evolve into a new posthuman species, or replace Homo sapiens with a population of intelligent machines, but over time these descendants of ours lose the capacity for conscious experience. Perhaps they continue to develop science, create works of art, and debate philosophy, yet there is nothing it is like to be them. They are philosophical zombies with no inner qualitative mental life. Since consciousness is necessary for sentience, these future beings wouldn’t count as human, if “human” is defined as “sentient beings that matter.” Consequently, humanity would no longer exist, which is enough to satisfy the minimal definition of extinction.

The same goes for definitions of “humanity” that emphasize moral status, since many philosophers believe that having moral status requires, at minimum, the capacity for conscious experience.⁹ Or imagine a scenario in which our descendants become much less “intelligent” than us. On the most capacious definition above, where “humanity” denotes “Earth-originating intelligent life,” these future beings wouldn’t be human, even if they were conscious. If one believes that the continued existence of “humanity” is important, this outcome might constitute a tragedy on par with final human extinction.

The key idea behind normative extinction is that it matters not just that we have successors, but what these successors are like.

(6) Premature extinction: this introduces the idea that the timing of our extinction, in any of the senses above, matters. If one holds a teleological vision of the human enterprise as striving toward some treasured goal, then one might claim that disappearing before we reach this goal would be worse than disappearing after it. Perhaps the goal is to create a techno-utopian world among the stars, or to construct a complete scientific theory of everything. One might argue that extinction after achieving these goals would still be very bad, but extinction before would be a much greater tragedy. On this account, what matters isn’t just whether our extinction happens, but when.

Distinguishing between these extinction scenarios is important because some positions within Existential Ethics see certain types of extinction as very bad, while assessing others as neutral or even good under certain circumstances.¹⁰ Other positions evaluate all the scenarios the exact same way, while still others point to just a single type of extinction as important. Failing to recognize that “human extinction” is highly polysemous—that it can have many different meanings—is a recipe for confusion and merely verbal debates, in which people appear to have a substantive disagreement, when in fact they’re using the same words to denote quite different things. For existential ethicists to make progress in the field, it is crucial for them to understand these different scenarios and the complex ways that different definitions of “human” fit with each.

So, whenever someone asks you: “Would human extinction be bad?,” the first thing you should do is huff back: “What do you mean by ‘human’?” and “What do you mean by ‘extinction’?” Only once you’re clear about the question can you begin to answer it coherently.

2.4 The Prototypical Conception

If “human extinction” can mean so many different things, what do most people have in mind when they think of this happening? What is the “prototypical conception” of human extinction? My hypothesis in the book is that this conception consists of three components.

First, most people naturally assume that “human” means “Homo sapiens,” rather than “future conscious beings with a certain moral status that are genealogically or causally related to us.” Second, in my experience, if someone is asked to define “extinction,” they will typically give the definition of “demographic extinction.” This is, in fact, the standard dictionary definition. If I follow-up with a question about whether our extinction might be temporary, they respond that it would surely be permanent (terminal extinction), and if pressed further, they tend to converge on the notion of final extinction: our extinction would be a complete and final end to the entire human story, an exclamation point at the end of this whole journey we are on, with nothing after it. Hence, most people take “human extinction” to mean “the final extinction of Homo sapiens.” But there is also an etiological, or causal, component of this conception, as most people automatically picture the final extinction of Homo sapiens happening as the result of some catastrophe. In other words, few if any of us imagine everyone on Earth choosing not to have children when we think of human extinction. Rather, we visualize a nuclear war, global pandemic, or asteroid impact when the idea comes to mind.

This is the prototypical conception, the primary focus of History #1. To be clear, there were people who addressed other types of extinction—Xenophanes was concerned with demographic extinction, and some writers after Darwin considered phyletic extinction—but in general, most thoughts about the possibility, probability, and so on, of human extinction involved the prototypical conception. Whether I am right about this being the most common conception today is not clear. Perhaps psychologists or sociologists will conduct a survey to test the hypothesis.

2.5 Going Extinct Versus Being Extinct

There is one last set of distinctions that are just as important as the six extinction scenarios. Consider the question: Are you afraid of death? Some people will say that the only reason they fear death is the suffering that dying might involve. Others will say that they’re afraid of not just the suffering but the subsequent state of no longer existing. For them, non-existence is a source of death’s terror in addition to the harms of dying. Moving from the level of individuals to the level of our species—from death to extinction—one can make an identical distinction between the process or event of Going Extinct and the state or condition of Being Extinct. This is an absolutely crucial distinction for Existential Ethics, which is orthogonal to every type of extinction outlined above. That is to say, there is Going Extinct and Being Extinct in the demographic sense; Going Extinct and Being Extinct in the phyletic sense; and so on. Whether one sees Being Extinct as ethically and evaluatively important, or whether one believes that the details of Going Extinct are all that matter, makes all the difference when it comes to which position one accepts within Existential Ethics.

What sorts of “details” about Going Extinct might be important? There are several. The most obvious is whether human extinction, however defined, is the result of natural or anthropogenic causes. There is nothing immoral about an asteroid hitting Earth and killing every human, since asteroids are not moral agents: they cannot be held morally responsible for anything. Ethics only cares about the actions of moral agents—creatures capable of being held morally responsible for their choices—and hence asteroid impacts fall outside the purview of ethics. However, if astronomers were to see this asteroid heading toward Earth, but instead of sending a spacecraft to redirect it they keep their discovery a secret, then this might well be an ethical issue, as we might count it as “anthropogenic” rather than “natural,” even though the asteroid itself is a natural phenomenon. Hence, where one draws the line between natural and anthropogenic is very important. I explore this in chapter 7 of the book, but won’t say anything else about it here.

Another distinction is whether Going Extinct is voluntary or not. Some philosophers argue that if causing or allowing our extinction were entirely voluntary, without any coercion at all, then it would not be wrong. Others claim that it would be wrong—perhaps very wrong—even if everyone on Earth voluntarily gave it a big thumbs up. For them, the voluntariness of extinction is morally irrelevant. A final distinction concerns how quickly Going Extinct happens. According to some philosophers, if our extinction were to happen in a flash without any prior warning, it wouldn’t be bad, because no one would suffer. (I mentioned above that this could theoretically happen. One could even imagine an omnicidal billionaire in the future building a particle accelerator in hopes of “nucleating” a vacuum bubble to destroy all life in an instant.) However, some of these very same philosophers argue that if Going Extinct were to cause suffering, then it would indeed be very bad.

In sum, it’s absolutely vital to distinguish between Going Extinct and Being Extinct. And there are many ways that Going Extinct could unfold that are ethically and evaluatively relevant, such as whether it is anthropogenic or natural, voluntary or involuntary, and instantaneous or drawn-out.

2.6 Positions Within Existential Ethics

We have now established a theoretical framework for making sense of Existential Ethics. Before turning to the historical development of this field, though, it may be worth engaging in one last abstract philosophical task: sketching the different positions that one could take on the subject, based on the distinctions made above.

There are three main classes of views within Existential Ethics. I call these equivalence views, further-loss views, and pro-extinctionist views. There are two additional positions that are also important: the default view and the no-ordinary-catastrophe thesis. Let’s examine these in turn, skipping over the no-ordinary-catastrophe thesis for now. To keep the conversation manageable, I will assume that we are talking about final extinction unless otherwise noted.

(1) The default view simply states that human extinction would be bad if the process or event of Going Extinct were to cause suffering and/or cut lives short. I call this the “default view” because virtually everyone accepts it, even most philosophers who are for extinction. The only people who might reject it are sadists and ghouls who derive pleasure from the thought of 8 billion people—including themselves—dying. The default view is mostly uncontroversial.

(2) Equivalence views claim that the default view is the entire story. Those who accept the equivalence view would argue that the badness or wrongness of our extinction is entirely reducible to the badness or wrongness of Going Extinct. If there is nothing bad or wrong about Going Extinct, then there is nothing bad or wrong about extinction, period.¹¹ Put yet another way, the badness/wrongness of human extinction is equivalent to the badness/wrongness of how Going Extinct unfolds, which is why I call these “equivalence views.”

To illustrate, imagine two worlds: in World A, there are 11 billion people, while in World B, there are 10 billion. An identical catastrophe happens in each, causing exactly 10 billion people to perish. At a high level of abstraction, we can say that one event happens in World A—the death of 10 billion people, leaving 1 billion survivors—while two events happen in World B—the death of 10 billion people and the extinction of humanity. The important question is: does this second event in World B make any ethical or evaluative difference? Is the catastrophe in World B worse than the catastrophe in World A because it eliminates humanity? If a homicidal maniac named Joe kills 10 billion people in each world, does he do something extra wrong in World B compared to World A?

An equivalence theorist will say that the catastrophe in World B is no worse than the one in World A, and that Joe does not do anything extra wrong in World B compared to World A. Why would someone hold this view? One popular answer is that if there’s no one around to bemoan the non-existence of humanity, then Being Extinct cannot be bad or wrong to cause—it harms no one.¹² The process or event of Going Extinct may very well be bad or wrong, and hence the equivalence theorist would say that, by killing 10 billion people, Joe did something unimaginably awful. But once the deed is done and humanity is no more, who exactly is harmed by Being Extinct? No one, which is why all that matters for equivalence theorists are the details of Going Extinct.

An interesting implication of this view is that there is no unique moral problem posed by our extinction. Everything one might say about the badness or wrongness of extinction can be said in ordinary moral language: 10 billion people suffering and dying in World B is very bad because human suffering is bad. Killing 10 billion people in World B is very wrong because murder is very wrong. The fact that humanity itself disappears in World B is just not morally relevant. Many philosophers throughout history have held equivalence views, and I myself am most sympathetic with it.

(3) Further-loss views strongly disagree with these claims. Advocates of such views would argue that, when assessing the badness/wrongness of human extinction, one needs to examine two things: first, the details of Going Extinct. Did the process of dying out cause suffering or cut lives short? And second, certain additional losses or “opportunity costs” associated with Being Extinct. What might these additional losses be? Some would point to all the happiness that could have otherwise existed, if humanity had survived. On one count, there could be at least 10^58—that’s a 1 followed by 58 zeros—people in the future. If these people were happy on average, then the total amount of happiness lost by not existing would be astronomically large. Others would point to goods like the further development of the sciences, the arts, and even morality itself. Being Extinct would erase future accomplishments in these domains before we have a chance to draw them.

Further-loss theorists thus argue that the badness or wrongness of extinction goes above and beyond whatever harms Going Extinct might entail: there are also various further losses, associated with Being Extinct, that are ethically and evaluatively important. An interesting implication of this is that our extinction could still be very bad or wrong even if there is nothing bad or wrong about Going Extinct. Imagine that everyone around the world voluntarily chooses not to have children. Over the course of 100 years or so, the human population dwindles to zero. Would this be bad or wrong? Equivalence theorists would say “no,” since there is nothing bad or wrong about not having kids. Further-loss theorists would say “yes,” because dying out would foreclose the realization of all future goods and happiness.

Returning to the Two Worlds thought experiment above, further-loss theorists would say that the catastrophe of World B is much worse than the catastrophe of World A, and that Joe does something extra wrong in World B compared to World A. How much worse or more unethical is the catastrophe of World B? It depends on one’s assessment of the further losses: the greater the losses arising from Being Extinct, the more tragic World B will appear.¹³

(4) The last position within Existential Ethics is what I call pro-extinctionism. This states that Being Extinct would in some way be better than Being Extant, or continuing to exist. As alluded to earlier, nearly all pro-extinctionists accept the default view: they believe that if Going Extinct involves harms, it would be bad or wrong. They simply add that the subsequent state of no longer existing would be better. Notice that “better” does not imply “good.” One could hold that Being Extinct is bad—even very, very bad—and still believe that Being Extant is worse.

The main problem for pro-extinctionism concerns how to get from here to there, from Being Extant to Being Extinct. There are three main items on the menu of options: antinatalism, whereby enough people around the world stop having children; pro-mortalism, whereby enough people around the world take their own lives; and omnicide, whereby someone or some group kills everyone on Earth. The large majority of pro-extinctionists have held that antinatalism is the only morally acceptable means of transitioning to the state of Being Extinct, although a very small number have advocated for pro-mortalism and even omnicide.

Returning once again to the Two Worlds thought experiment, pro-extinctionists would claim that if they were forced to choose between World A and World B, they would pick World B. Why? One answer is that by causing our extinction, this would prevent a potentially large amount of future human suffering from existing. Others would point to environmentalist reasons, arguing that humanity has been a hugely destructive force in the biosphere, and hence without us, the natural world would be better off.

2.7 Which Type of Extinction Matters?

We can see from this brief survey just how important the distinction between Going Extinct and Being Extinct is for Existential Ethics. But what about the different types of human extinction? How do they fit into this picture? Let me illustrate with a few examples.

First, let’s say that you hold a further-loss view according to which what matters is that the future contains maximum value. You also believe this value cannot be created if our descendants lack a certain moral status, are incapable of conscious experiences, and so on—properties that some of the normative definitions of “humanity” attempt to capture. Does it matter whether Homo sapiens persists? No. So long as we have successors with the right properties, the future could still contain large amounts of value. In other words, the terminal extinction of Homo sapiens would not be inherently bad or wrong to bring about. The only types of extinction that must be avoided, on this view, are final and normative extinction.¹⁴

We may still have practical reasons to avoid demographic extinction in the near future, since if this were to happen tomorrow, it would almost certainly coincide with final extinction, by way of terminal extinction.¹⁵ But if we are, as some claim, on the cusp of creating sentient, intelligent machines that could replace us, then demographic extinction would only be important to avoid if it were to happen before these machinic replacements arrive. Our disappearance after they arrive wouldn’t be any great tragedy, since these posthuman beings could create maximum value in the universe even if we no longer exist—indeed, they may be much better positioned to do this than we are.¹⁶ This is why some further-loss views will identify final and normative extinction as the only two scenarios that must be prevented at all costs.

What about equivalence theorists? Since they do not see extinction as posing any unique moral problem, their view applies to every type of human extinction equally. Would demographic, phyletic, terminal, and so on, extinction be bad or wrong? It depends on how these come about. If there is nothing bad or wrong with Going Extinct in any of these senses, then there is nothing bad or wrong, period.

As for pro-extinctionists, if the aim is to prevent future human suffering or the harms that we cause to the biosphere, then one should hope not just that our species dies out but that we don’t have any successors. If Homo sapiens disappears while leaving behind successors who are capable of suffering or destroying the biosphere even more, the problem that pro-extinctionism aims to solve will remain. Hence, when most pro-extinctionists talk about “human extinction,” they are referring to “final human extinction.” This is the one type of extinction that would guarantee no more human suffering or environmental destruction in the future. There are some interesting nuances here, but I will pass over them for now.

We can now see why disambiguating the term “human extinction” is so important. The fact that so many disparate scenarios are referred to by the same term can easily lead to confusion and merely verbal debates. The types of extinction that the three main positions within Existential Ethics target may be very different. Understanding this is necessary for the field to progress.

Section 3. History #2—Existential Ethics

3.1 The Four Waves

Having established a theoretical framework for making sense of Existential Ethics, we can now turn to its historical development. In Part II of the book, I suggest that History #2 can be partitioned into four vaguely defined “waves,” which align with the five-part periodization of History #1 in a somewhat complicated way. Whereas the existential moods of History #1 are a real feature of the Western historical record, I take these waves to be nothing more than a useful way of organizing History #2. Let’s consider them in turn:

3.2 The First Wave

The first wave began with the birth of Existential Ethics in the 19th century. This makes sense, since there’s no especially good reason to reflect on the ethics of something that no one believes is possible or could actually happen. In particular, it was the second half of the 19th century that witnessed more than a few philosophers addressing the core questions of Existential Ethics. However, there were earlier writers who touched upon the topic, all of whom held either non-traditional religious views or rejected religion altogether.

One was the Enlightenment deist Montesquieu. In his 1727 epistolary novel Persian Letters, he argues that the human population is declining, and that if this continues, humanity will cease to exist. Of note is that he—speaking through a character in the novel—describes this event as “the most terrible calamity that can ever happen in the world.” What I find interesting about this is that Montesquieu seems to point at Being Extinct as a source of badness, rather than the harms that Going Extinct might cause, although he did not elaborate on why. Perhaps he believed the answer was obvious: a world without us would be missing something important. As the philosopher Immanuel Kant expressed this very idea in 1790, “without men the whole creation would be a mere waste, in vain, and without final purpose.”

The first writer to elaborate a further-loss view in print was probably Mary Shelley. In her 1826 novel The Last Man, she made two interesting claims: first, she foregrounded the possibility that Going Extinct could introduce extra suffering to the last generation on Earth, because it’s the last generation. A common response to someone going through a difficult time is to say that “it’s not the end of the world.” But if it is the end of the world, this source of comfort won’t work. The final generations, and the last remaining people of those generations, may experience feelings of dread, hopelessness, and loneliness that other catastrophes might not induce. This is the central thrust of the “no-ordinary-catastrophe thesis,” mentioned in the previous section. Although one might find this thesis a bit peculiar at first, many existential ethicists have referenced it.¹⁷ Shelley was among the first.

But Shelley also suggested that our extinction—which she seemed to understand in a naturalistic sense—would be bad independent of all the suffering caused by Going Extinct. At one point in the novel, she lists “adornments” of humanity like knowledge, science, technology, poetry, philosophy, sculpture, painting, music, theater, and laughter as further losses that would make our disappearance extra tragic. Without humanity, none of these would exist, which points to Being Extinct as a source of badness, too.

Another figure who defended a further-loss view was the philosopher Henry Sidgwick, although not until half a century later. In his 1874 tome The Methods of Ethics, Sidgwick considered acts that may be morally permissible for individuals to do on the assumption that they won’t be widely imitated. The example he used was celibacy: there is nothing wrong with people choosing not to have sex, but if a very large number were to do this, the result would be extinction, and that would be very bad. Hence, he declared that “a universal refusal to propagate the human species would be the greatest of conceivable crimes from a Utilitarian point of view.”

As this indicates, Sidgwick was a utilitarian—in particular, a totalist utilitarian, where “totalism” is the idea that the more total happiness that exists in the universe as a whole, the better the universe will become. Since one way for there to be more total happiness is for there to be more happy people, totalist utilitarianism instructs us to increase the human population. There are two ways to do this: synchronically, meaning that we increase the number of people right now by having more children, and diachronically, meaning that we make sure that people exist in the future, extended across time. Since human extinction would prevent us from doing the latter, Sidgwick concluded that even if Going Extinct were entirely voluntary, it would still be a great moral crime. This is the heart of his further-loss view: the badness of extinction arises at least in part from the opportunity costs of Being Extinct—all the lost happiness if there are no future people.

Around the same time that Sidgwick was writing, a group of philosophers in Germany were outlining a diametrically opposed view. These philosophers were “pessimists” in the sense that they believed that the world is very bad and life is full of suffering, a position famously defended by Arthur Schopenhauer. (A very similar view is found in Buddhism, as the First Noble Truth states that life is “duḥkha,” or dissatisfaction, often translated as “suffering.”) Consequently, some pessimists contended that Being Extinct would be better than Being Extant, and hence we should try to bring about the former—a state marked by the “blessed calm of non-existence,” borrowing a line from Schopenhauer.¹⁸

How? According to Philipp Mainländer, we should refuse to have children by choosing virginity; if we are not virgins, we should become celibate. But Mainländer also endorsed suicide, to an extent, and in fact when he received the first copies of his magnum opus, The Philosophy of Redemption, he placed them on the floor, stood on top of them, and hanged himself.

The pessimist Eduard von Hartmann, a contemporary of Mainländer, proposed something different. He argued that we should strive to end not just humanity, but all life in the universe. He never specified a means of doing this, arguing instead that as culture and technology progress, the right method will come into view. This is why some have described his position as “optimistic pessimism.” Our lives have a purpose; we have a reason to live, prosper, and create new generations. By contributing to the further development of our culture and consciousness, we will eventually reach a point at which the horror show of existence can be terminated once and for all. Since Hartmann was a metaphysical idealist, he believed that the universe cannot exist if it contains no subjects—beings like you and I. Hence, by eliminating all subjectivity, the universe itself would cease to be.

Hartmann attained a celebrity status in his time, though German pessimism declined in popularity around World War I, and few people today know who Hartmann is. Nonetheless, there were still some pessimists in the early 20th century who shared the pro-extinctionist views of Hartmann and Mainländer.

An example is the Norwegian philosopher Peter Wessel Zapffe. In a rather moving essay titled “The Last Messiah,” Zapffe argued that humans have become over-evolved. He compared us to the Irish elk, a species that some believed went extinct because it evolved antlers so large that males could no longer hold their heads up. Zapffe claimed that the same thing has happened to humans with respect to our consciousness. Our unique capacity to contemplate the suffering and evils of the world has become maladaptive. Whereas all animals “know angst, under the roll of thunder and the claw of the lion,” the human being “feels angst for life itself—indeed, for his own being.” The result is a kind of “cosmic panic” that we cannot escape, although we have devised defense mechanisms to help us deal with this. These mechanisms are the only way that we’ve avoided “great, raging epidemics of insanity.” The solution, Zapffe argues, is to stop replacing ourselves—to refuse to have children. If humanity disappears, so does the cosmic panic that grips us whenever our defense mechanisms fail, forcing us to look the terrors of existence straight in the eyes.

Yet there were also philosophers during this first wave to address Existential Ethics from a rather different perspective. These reflections do not clearly fit into the categories of equivalence, further-loss, or pro-extinctionists views, as they focused on questions of life’s meaningfulness given the scientific eschatology of the Second Law. What does anything matter if, in the end, all will be lost? Bertrand Russell provides a poignant example. In his 1903 essay “A Free Man’s Worship,” he channeled the prevailing existential mood in writing that our dismal fate in the universe conjures up a sense of “unyielding despair,” given that

all the labours of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast death of the solar system, and that the whole temple of Man’s achievement must inevitably be buried beneath the debris of a universe in ruins.

This essay was widely circulated in the early 20th century, but it echoes—sometimes using almost the same words—an earlier article by the British statesman Arthur Balfour, who made a similar point about the implications of thermodynamics. However, Balfour used this as an argument against atheism: without a belief in our immortality or a sense of eschatological hope for the future, one is left despondent. Despite Balfour’s pleas, the tides of secularization continued to rise.

These are among the very few instances of anyone addressing the central questions of Existential Ethics during the first wave.

3.3 The Second Wave

The second wave arose shortly after the third existential mood solidified, following the Castle Bravo debacle of 1954. It witnessed a veritable explosion of new ideas about the ethical and evaluative implications of our extinction, and witnessed the first vigorous defenses of the equivalence view. The chapter that discusses this wave is the longest in the book, so I cannot do it justice in this short document. I’ll focus on a few key contributions.

We begin with the German philosopher Günther Anders, the earliest postwar philosopher to seriously address the ethics of nuclear omnicide. In my book, I provide the first extended analysis of Anders’ views on the matter, which have been almost entirely ignored by Anglophone philosophers until quite recently. Anders argued that the Atomic Age, especially after the invention of thermonuclear weapons, has inaugurated a new epoch in human history. Whereas the past is characterized by the fact that “all human beings are mortal,” nuclear weapons have irreversibly transformed our existential predicament. Now, “humankind as a whole is killable.”

The significance of this transformation, he claimed, is beyond our comprehension. Consequently, we have become “inverted Utopians.” Whereas “ordinary Utopians are unable to actually produce what they are able to visualize, we are unable to visualize what we are actually producing,” namely, a situation in which total human annihilation has become feasible. The result is a “widespread and disastrous ailment” that he called—in dated language—“apocalyptic blindness,” by which he meant an inability to grasp just how dire our predicament may be. If a nuclear holocaust were to destroy humanity, not only would billions of current-day people die horrible deaths, but our disappearance would delete the memories of all those who came before us. “We would make them die, too—a second time, so to speak,” such that “after this second death everything would be as if they had never been.” Human extinction would also erase all future generations, which Anders described as our “neighbors in time,” since the act of “setting fire to our house … cannot help but make the flames leap over into the cities of the future, and the not-yet-built homes of the not-yet-born generations will fall to ashes together with our homes.”

Anders thus held a further-loss view according to which the further losses include the memories of past people and all the future generations that could exist. Hans Jonas, another German-Jewish philosopher, also defended a further-loss view. On his account, since humans are the only creatures capable of being held morally responsible for our actions, we are “the foothold for a moral universe in the physical world.” Without us, the moral universe would evaporate, which Jonas believed would be very bad. Consequently, he proposed a new moral imperative, which says: “Act so that the effects of your action are compatible with the permanence of genuine human life.” This is the essence of Jonas’ view, although the theoretical edifice that he builds around it is quite intricate and nuanced.

About the same time—in the late 1960s and early 1970s—a number of philosophers articulated an equivalence view of human extinction. Jan Narveson, for example, proposed a version of utilitarianism that rejects Sidgwick’s claim about maximizing happiness in the universe as a whole. Rather, he argued that our only duty is to maximize the happiness of those who already exist. This means that there is no moral obligation to create more happy people, and indeed if everyone were to decide to stop having children, that would not be wrong. As Narveson wrote, “is there any moral point in the existence of a human race, as such? That is to say, would a universe containing people be morally better off than one containing no people? It seems to me that it would not be.” Although Narveson was clear that he does “want to keep the human race going,” he described this as “purely a matter of taste,” rather than an ethical stance.

Other philosophers at the time agreed, such as Jonathan Bennett. Bennett was also the first to propose what’s called the “argument from unfinished business,” which states that our extinction would be worse if it were to occur before attaining some valued end-goal. This was probably the first reference in the Existential Ethics literature to premature extinction, although Bennett never used the term. That said, he considered the failure to “finish” certain “business” to be bad in an aesthetic rather than moral sense, not unlike Narveson’s preference for humanity to persist.¹⁹ This matters because moral claims tend to have much more force than aesthetic ones, as I explain in a recent article about Existential Ethics for Aeon.

Still others argued that Being Extinct might be desirable, and that the only reasons a nuclear catastrophe would be bad arise from the harms that Going Extinct would involve. Hermann Vetter declared in 1968 that “if mankind were extinguished by a nuclear war, the real evil … would be the way the extinction would take place: there would be so much terrible suffering for so many people before they die that this is a tremendous evil.” However, “if mankind were completely extinguished in a millionth of a second without any suffering imposed on anybody, I should not consider this as an evil, but rather as the attainment of Nirvana.”

The late 1970s and early 1980s saw a resurgence in further-loss views associated with totalist utilitarianism. One philosopher who defended this position was Jonathan Glover, who wrote that “to end the human race would be about the worst thing it would be possible to do.” Another was Derek Parfit, one of the most influential moral philosophers of the 20th century. In the final paragraphs of his 1984 book Reasons and Persons, Parfit asked his readers to imagine three scenarios: (1) peace, (2) a nuclear war that kills 99% of humanity, and (3) a nuclear war that kills 100% of humanity. He then asked whether the greater difference in badness is between (1) and (2) or (2) and (3). Equivalence theorists would say it’s between (1) and (2), but Parfit contended that it’s between (2) and (3), since that last 1% of humanity dying out would foreclose a potentially vast amount of future human happiness.

But Parfit also endorsed a further-loss view that Sidgwick would have rejected: whereas for Sidgwick, all that mattered was happiness, Parfit also pointed to science, the arts, and even further developments in ethics as additional losses that would make our extinction bad. He concluded, using almost the very same language as Sidgwick, that “the destruction of mankind would be by far the greatest of all conceivable crimes.”

An important part of Parfit’s argument comes from a branch of cosmology called “physical eschatology,” which studies the future evolution of the cosmos, including our solar system. This field emerged in the 1970s, and early research suggested that Earth could “remain inhabitable for at least another billion years,” to quote Parfit. By contrast, human civilization is only about 6,000 years old, and our species emerged roughly 300,000 years ago. It follows that there could be many orders of magnitude more people in the future than have so far existed—about 117 billion. The first person to give an estimate of how many future people there could be, so far as I know, was Carl Sagan in 1983. He calculated that if humanity persists for just another 10 million years, some 500 trillion people could be born, which is more than 4,000 times the number of past people. All these future people would be lost if humanity were to die out. Similarly, this vast expanse of future time could enable our descendants to advance science, create works of art, and so on, so marvelous that we cannot even begin to imagine them. These wonders would also be lost with extinction. Hence, for these two reasons, Parfit rejected the view of Narveson and Bennett, claiming instead that the tragedy of human extinction would go far beyond whatever harms Going Extinct might cause.

A final contribution to this second wave that’s worth examining comes from the journalist Jonathan Schell. In his brilliant 1982 book The Fate of the Earth, Schell defended a number of arguments for why our extinction would be very bad. One of these is the “argument from impoverishment,” as I call it. This states that the threat of total annihilation seriously undermines the value or meaningfulness of our lives in the present. “Because the unborn generations will never experience their cancellation by us,” he wrote, “we have to look for the consequences of extinction before it occurs, in our own lives, where it takes the form of a spiritual sickness that corrupts life at the invisible, innermost starting points of our thoughts, moods, and actions.” Without the assurance that posterity will exist, “nothing else that we undertake together can make any practical or moral sense,” to which he adds that “all human activities that assume the future are undermined directly” by the prospect of extinction. Hence, it is only “by acting to save the species, and repopulating the future, [that] we [can]] break out of the cramped, claustrophobic isolation of a doomed present, and open a path to the greater space—the only space fit for human habitation.”

Although Schell did not cite Anders, and probably never read Anders’ writings, he labeled the expungement of humanity the “Second Death.” Tying this to claims from section 2, whereas equivalence theorists do not see the Second Death as morally significant, further-loss theorists very much do. In the Two Worlds thought experiment, what makes World B worse than World A, on the further-loss account, is precisely that it entails the Second Death of humanity. Even more, some further-loss theorists like Schell would argue that the Second Death is the worst aspect of our extinction, even if Going Extinct causes loads of suffering.²⁰ The Second Death would be an “even huger” catastrophe than “the untimely death of everyone in the world,” in Schell’s words. This idea has become very popular over the past decade, as we’ll explore just below.

The second wave in Existential Ethics thus covers a wide range of different views. All three major positions within the field—equivalence, further-loss, and pro-extinctionist views—were defended by notable philosophers, and novel arguments like those from unfinished business and impoverishment were proposed. This wave also saw the rise of pro-extinctionists who advocated for our non-existence based on environmentalist considerations: humanity has been a profoundly destructive force within the biosphere, and hence it would be best if we followed the dodo into oblivion. Environmental pro-extinctionism is what inspired a deep ecologist named Les U. Knight to found the Voluntary Human Extinction Movement in 1991. Its aim was to catalyze our extinction by persuading people not to have children, for the sake of the environment. There were also some radical environmentalist groups that endorsed omnicide—the murder of everyone—like the Gaia Liberation Front. The book goes into detail about these ideas, groups, and movements, although we will skip over them for now.

3.4 The Third Wave

The third wave covers two major developments: the rise of “longtermism,” and the first systematic defense of antinatalism in 2006. Let’s examine these in order.

The genealogy of longtermism stretches back to Sidgwick and runs through the work of 20th-century philosophers like Glover and Parfit. But it was developed most significantly by Nick Bostrom and others in the TESCREAL community over the past two decades. I regret that I treat Bostrom as a legitimate contributor to Existential Ethics in my book, given Bostrom’s recently uncovered history of racist remarks (including the N-word) and his long-time advocacy of eugenics. (The most egregious remark from Bostrom wasn’t discovered until after a final draft of my book was submitted.²¹) Nonetheless, Bostrom’s publications have been very influential, shaping the worldviews of some of the most powerful people in the world, including Elon Musk, and hence History #2 would be incomplete without discussing them.

At the core of longtermism is the recognition, drawn from physical eschatology, that our potential future in the cosmos could be enormous. Although Earth will become uninhabitable in a billion years or so, if we spread into space and colonize other galaxies, we could persist for at least another 10^40 years, at which point protons might decay. However, physicists are unsure if protons will decay. If they don’t, our spacefaring descendants might stick around for another 10^100 years, the estimated time of the heat death. Even more, the universe is huge, and consequently the future human population could become far larger. This is especially true if future people are digital rather than biological, since we can cram more digital people per volumetric unit of space than biological people. In 2003, Bostrom estimated that there could be 10^38 digital beings—that’s a 1 followed by 38 zeros—per century in the Virgo Supercluster alone, a cluster of clusters of galaxies that includes the Milky Way. Roughly 10 years later, he calculated that some 10^58 digital beings could exist in the universe as a whole.

This means that the further losses associated with Being Extinct would be quite literally astronomical. Bostrom called any event that would prevent us from creating astronomical amounts of value in the utopian future that awaits us an “existential risk.” Of note is that human extinction—specifically, in the final or normative senses—is not the only way that an existential catastrophe could happen. Drawing from others at the time, Bostrom realized that there could be various survivable scenarios that also keep this value from existing. For example, scientific and technological “progress” could stagnate, thus making it impossible for us to fulfill our “longterm potential” in the universe. If future humans decide not to develop the technologies needed to colonize space or become posthuman, an existential catastrophe would occur even though extinction has not.

A central aim of longtermism, therefore, is to mitigate existential risks, including the risk of total extinction. We can distinguish between two versions of this ideology: according to “moderate” longtermism, ensuring that the long-term future of humanity goes well is a key moral priority of our time. On a “radical” interpretation, this is the key priority. The longtermist worldview has become quite widespread in Silicon Valley and among the tech elite, and is shaping the policies of major governing bodies. As a UN Dispatch article reports, “the foreign policy community in general and [the] United Nations in particular are beginning to embrace longtermism.” Musk has tweeted that longtermism is “a close match for my philosophy,” and much of the rhetoric about AGI existential risks comes from the longtermist—or, more generally, the TESCREAList—community. Due to the power and influence of this ideology within certain slices of society, further-loss views have become arguably the most widely accepted position in Existential Ethics today.

Historically, the further-loss view associated with longtermism played an integral role in inspiring novel efforts in the late 1990s and early 2000s to catalogue every possible threat to our collective survival.²² It’s what drove the futurological pivot, which shifted attention toward the various emerging and anticipated future threats that humanity might encounter this century, before we’ve spread to other planets. This is where the causal relations between History #1 and History #2 reversed in a momentous way: rather than the discovery of new kill mechanisms provoking thoughts about our extinction, thoughts about our extinction—about its unfathomable badness—spurred efforts to discover new kill mechanisms. Only by mapping out the entire threat environment can we ensure our march toward astronomical value in the far future. Whereas History #1 shaped key features of History #2 across the first two waves, this flipped at the turn of the 21st century, with the emergence of the third wave and the fifth existential mood.

Yet, at the very same time that Bostrom and others were developing the longtermist ideology, a South African philosopher named David Benatar published the first comprehensive defense of antinatalism. In fact, it was his 2006 book Better Never to Have Been that introduced the word “antinatalism” to the philosophical lexicon. (My use of this word to describe earlier views is thus anachronistic, although still accurate.) As with Bostrom, Benatar has a checkered past, which leads me to regret giving him so much space in the book. But his views have also been influential among philosophers, sparking a small but lively debate in academic journals.

According to Benatar, birth is always a net harm. There are two reasons for this: first, he observes that existence involves both pleasures and pains. The presence of pleasure is good, while the presence of pain is bad. In contrast, non-existence involves neither pains nor pleasures. The absence of pain is good, while the absence of pleasure is not bad. Hence, if we compare existence with non-existence, we see that the former is a good/bad situation whereas the latter is a good/not-bad one. Since a good/not-bad situation is better than a good/bad one, non-existence is better than existence. Coming into existence thus causes net harm.

Why is the absence of pain, with respect to someone who’s never born, good rather than just neutral? Who exactly is it good for? Benatar does not provide a compelling answer. He insists that it’s good even though the person doesn’t exist to experience this absence. On the flip side, why is the absence of pleasure not bad? His response echoes the central insight of some equivalence views: if no one exists to be deprived of that pleasure, where is the harm? This makes his position look inconsistent: on the one hand, the absence of pain is good for the non-existent person, while on the other hand, the fact that this person doesn’t exist is what makes the absence of pleasure not bad. Some philosophers have argued that this is incoherent.

However, Benatar proposes a second reason that being born is harmful. This draws from and elaborates the claims of 19th-century German pessimists, especially Schopenhauer, who believed that life is very bad. There is chronic pain but no chronic pleasure; time tends to slow down when we experience pain, while it tends to speed up when we experience pleasure; the worst pains that we can experience are much greater than the best pleasures. For example, who would trade 10 years of extreme happiness for 24 hours of the most horrific torture? Most would say, after a moment’s reflection, that they would not take the offer.

Benatar thus concludes that it is wrong to bring people into the world. The implication is that humanity should go extinct by refusing to procreate. There are three main components to Benatar’s pro-extinctionist view: first, given the asymmetry between pains and pleasures mentioned above, Being Extinct wouldn’t just be better than Being Extant, it would be positively good. That is to say, Being Extinct would be a good/not-bad situation, since it would entail the absence of pain (good) and pleasure (not bad). Second, we should strive to bring about our extinction as soon as possible. There is a certain moral urgency to the situation, since the longer humanity exists, the more harms there will be, due to there being more births and more lives full of suffering. And finally, the only acceptable means of Going Extinct is by voluntarily choosing not to procreate. Benatar calls extinction through voluntary antinatalism a “dying-extinction,” which he contrasts with a “killing-extinction,” whereby humanity is involuntarily destroyed due to anthropogenic or natural phenomena. Hence, as with nearly all pro-extinctionists, Benatar is emphatic that omnicide is morally impermissible, although he leaves the door ajar to pro-mortalism, arguing that suicide can be more rational than most of us usually believe.

These were the two most important developments of the 21st century, at least until the past 6 years or so. This leads us to the final wave within Existential Ethics.

3.5 The Fourth Wave

I trace the origins of this fourth wave to a series of papers published since 2017. This wave is partly a response to the rise of longtermism, and a common feature that binds many of these contributions together is an approach to thinking about the ethical and evaluative implications of our extinction from a non-utilitarian or non-consequentialist perspective.

One such perspective comes from “contractualism.” This ethical theory states that an act is wrong if it were to violate a moral principle—specifically, a moral principle that no one could reasonably reject, after reflecting on it. Contractualism is ultimately about respecting the interests of other people, about ensuring that we can justify our actions to them. Unlike utilitarianism, it isn’t concerned with maximizing value. In a 2017 article, the philosopher Elizabeth Finneron-Burns notes that there are four main reasons that one might believe that causing or allowing our extinction is wrong: first, because it would prevent future people from existing. Second, because it would remove “the only known form of intelligent life” in the universe, and “all civilization and intellectual progress would be lost.” Third, because it could inflict physical harms on those living at the time of the extinction event, or cut their lives short. And fourth, because it could cause psychological anguish to those who experience the event.

On a contractualist view, only the third and fourth reasons are morally important; the first two are not. In other words, contractualism entails the equivalence view. It focuses entirely on the details of Going Extinct, while seeing the outcome of Being Extinct as morally irrelevant. Consequently, Finneron-Burns concludes that if Going Extinct were universally voluntary, there probably wouldn’t be anything wrong with it.

A different view was put forward the same year by the philosopher Johann Frick. His argument is based on the idea of “final value,” or the value that something has as an end in itself. This contrasts with “instrumental value,” or the value that something has as a means to an end. A hammer has instrumental value, whereas one could argue that a beautiful work of art has final value: it’s not valuable simply because looking at it gives you pleasure, or selling it gets you a few million dollars. It matters for its own sake, and the world would be impoverished without it. We commonly attribute final value to a range of things, such as cultures, languages, artwork, knowledge, and other species. So why not humanity, too? If humanity has final value, then we should want it to continue existing rather than dying out, because “what would it mean to value things, but in general, to see no reason of any kind to sustain them or retain them or preserve them or extend them into the future?” If I value a pocket watch passed down from my great-grandfather, I would be devastated if it were accidentally dropped on the street and run over by a passing vehicle. Valuing something in the “final” sense just is to want the valued thing to persist in good condition. Frick thus proposes what he calls the “argument from final value,” which states that the appropriate response to humanity itself being finally valuable is to ensure our continued survival—in other words, to prevent our extinction.

Not everyone over the past few years has held a pro-survival view. The Oxford philosopher Roger Crisp argues that there may be certain types of suffering that no amount of happiness or pleasure in the world could possibly counterbalance. Think of child abuse, torture, or violent genocides. Is there some quantity of goodness that can somehow make-up for these atrocities? Many people would say “no.” Consequently, if we have reason to expect them to exist in the future, then it might be better if humanity were to cease existing. Even though there could be lots of happiness in the future as well, this happiness wouldn’t counterbalance these terrible evils. Crisp thus asks us to imagine a large asteroid barreling toward Earth. Assuming that once it strikes, it would kill everyone immediately, he suggests that if it were in your power to safely redirect the asteroid away from Earth, you should seriously consider not doing this. Although Crisp does not claim that “extinction would be good,” he suggests that it might be.

Finally, I outline my own tentative views on the core questions of Existential Ethics. The position that I defend combines elements of all three positions that we’ve discussed, although it most closely aligns with the equivalence view. Here’s a brief overview:

When I imagine the human story ending, I’m struck by a sense of great sadness. As Shelley pointed out, there would be no more laughter, music, poetry, and knowledge. There would be no more tender moments between friends, no more expressions of human love and kindness. The memories of all those laid to rest would be lost forever, and the whole human drama of striving for a better world would be as if it had never been. The moral universe itself would evaporate, as Jonas noted, and the transgenerational projects of science and philosophy would come to an unsatisfactory conclusion. When I picture all the rich diversity of human cultures, languages, and traditions being erased, the badness of extinction does appear to extend above and beyond whatever harms Going Extinct might entail.

But two further considerations pull in the opposite direction. The first concerns the claim that if Being Extinct does not cause anyone harm, then where exactly is the wrong? Where is the badness? Who exactly would suffer the loss of everything listed above? Being Extinct is a victimless crime, and therefore no crime at all, contra philosophers like Sidgwick and Parfit. Even more, when I contemplate all the pain, heartache, misery, and loneliness in the world, all the tears shed and dreams unfulfilled, the loves lost and evils rewarded, it’s hard not to admit that the philosophical pessimists have a point. The world really is saturated with suffering, and some of this suffering might be of a kind that no amount of happiness could ever compensate for. Imagine being offered the chance to live the life of every human over the past 100 years. Would you do it? This would take you through all sorts of wonderful times—moments of intense felicity and joy—but it would also place you under the claw of indescribable anguish, trauma, and injury. Most people, after reflecting on this for a moment, would decline the offer. The good experiences would be enormous, but the bad experiences would be even greater—perhaps insurmountably so. If the future is like the past, then maybe there’s a sliver of truth to the claim that Being Extinct would be best.

However, by far the most probable ways of Going Extinct, of getting from here to that state of non-existence, would involve untold suffering and death. While it’s not obvious to me that voluntary human extinction by not replacing ourselves would be wrong, the probability of this happening is virtually zero. This means that if humanity goes extinct, it will almost certainly be the result of a terrible worldwide catastrophe. In the book, I foreground the fact that our minds, pieced together over millions of years by contingent evolution, are simply unable to comprehend just how bad an extinction-causing catastrophe would be. Ask yourself which of these two scenarios strikes you as worse: one innocent person dying instead of no one dying, or 43,985,542 innocent people dying instead of 43,985,541? In both cases, the difference is only one death, yet the extra death in the second scenario seems almost insignificant. As the mass murderer Joseph Stalin once quipped, one death is a tragedy, while a million deaths are a statistic. Applying this to the case of catastrophic human extinction, we simply cannot imagine the awfulness of 8,000,000,000 people—the global population right now—being involuntarily catapulted into the grave by a catastrophe that sweeps across the globe. Nor can we muster the appropriate emotional response to such a monstrous event. Recognizing this fact, though, can help us gain some perspective on the matter.

The practical component of my position, therefore, is that we should do everything in our power to prevent an extinction-causing catastrophe from occurring. Whether or not the badness of extinction goes beyond the details of Going Extinct (I’m inclined to say that it doesn’t, all things considered), the badness of an extinction-causing catastrophe would be inconceivably huge. This means that if you were to see an asteroid racing toward Earth and could do something to prevent a collision, you should, without hesitation, redirect the celestial body! Omnicide, even if passively allowed through inaction, and even if instantaneous, would be a profound and unequivocal evil. I do not think this could be overstated. Hence, I disagree with philosophers like Crisp and Vetter.²³

On the other hand, the equivalence view that I accept does not see extinction as a qualitatively unique sort of tragedy. Catastrophes that cause our extinction are different in degree rather than kind from ones that kill “only” millions or billions of people. Consequently, there is no reason to strongly prioritize mitigating extinction risks over all other problems that society is facing. This is where I vehemently object to further-loss views like totalist utilitarianism and longtermism. They see extinction as many orders of magnitude worse than non-extinction scenarios, which naturally inclines adherents to minimize or trivialize problems that don’t threaten to foreclose the potentially vast amounts of “value” that might exist if we don’t go extinct. Bostrom exemplifies this attitude when he describes the worst disasters of the 20th century, including the two world wars and AIDS pandemic, as follows: “Tragic as such events are to the people immediately affected, in the big picture of things—from the perspective of humankind as a whole—even the worst of these catastrophes are mere ripples on the surface of the great sea of life.” Why? Because “they haven’t significantly affected the total amount of human suffering or happiness or determined the long-term fate of our species.” When measured across the trillions and trillions of years that Earth-originating intelligent life could persist if we spread beyond Earth and colonize the accessible universe, disasters that strike but don’t destroy us fade into nearly imperceptible blips.

To illustrate the reasoning behind this, consider the figure below. The diagonal line indicates that, as the number of deaths increases, the badness of the catastrophe rises. Both equivalence and further-loss theorists can agree about this. However, the moment at which 100% of humanity disappears marks a critical moral threshold, at which point these views diverge in a very big way. For equivalence theorists, the badness of the situation plateaus once we transition to Being Extinct, since there are no more people around to be harmed by this state. For further-loss theorists, the badness suddenly increases, given the additional losses associated with no longer existing. How high the vertical arrow rises will depend, once again, on how substantial and significant one sees these losses. A longtermist who anticipates 10^58 happy digital people being lost forever might extend the arrow billions or trillions of times higher than its length in the figure.

This is why avoiding human extinction is disproportionately important to further-loss theorists. It’s why mitigating extinction risks should be strongly prioritized, even if this means shifting attention away from non-extinction-threatening problems like global poverty and social injustices. Hence, an advantage of my position is that it allows one to take extinction risks very seriously, but not at the cost of minimizing or trivializing other problems in the world.

Let’s close by returning to a point made in the introduction. The majority of people who’ve written about human extinction in the Western tradition have been white men. Why is this? One answer is that an extinction-causing catastrophe would directly affect the most privileged people in society, whereas things like global poverty and social injustices don’t. By adopting a further-loss view, these privileged people give themselves a “moral excuse” to prioritize a class of catastrophes that just so happen to threaten them, while simultaneously adopting a dismissive or insouciant attitude toward problems that don’t endanger our “vast and glorious” future among the stars, to quote the longtermist Toby Ord. Further-loss views like longtermism can be self-serving. This does not necessarily mean that they are wrong, only that one should be suspicious when the most privileged and powerful people declare that reducing the risks of extinction, however speculative or improbable, should be prioritized over all else.

Conclusion

This is a very brief overview of Human Extinction. I’ve passed over a lot of important details, but hope that this offers a useful guide to some of the main ideas. Key concepts from Part I include: existential moods, enabling conditions, triggering factors, and existential hermeneutics. I argue that Western history can be divided into five well-defined periods, each corresponding to a different existential mood. Important ideas from Part II include: the six extinction scenarios, the distinction between Going Extinct and Being Extinct, the three major positions within Existential Ethics, and the four historical waves. Here’s the very last paragraph of the book, which captures my sense of futurological hope and dread, as well as my uncertainty about the right course of action:

This is a long book that has offered only the briefest glimpse of its topics. The story is not over yet, and its ending is ultimately up to us. May we have the wisdom to do whatever we should.

Appendix 1

Consider another thought experiment that highlights the differences between the three main positions in Existential Ethics. As shown, more people exist right now in World X than World Y, although more people would exist in World Y than World X if not for a global catastrophe that annihilates humanity, indicated by the gray line. Which catastrophe scenario would be worse? For equivalence theorists, World X would be worse, since Going Extinct causes a greater number of people to suffer and die. For further-loss theorists like totalist utilitarians and longtermists, World Y would be worse, since the opportunity costs of World Y are greater—all the future lives that could have existed and all the value they could have created. If you find yourself agreeing that World X would be worse, then you probably aren’t a totalist utilitarian or longtermist.

However, there’s an important nuance: not all further-loss views would agree that World Y would be worse. Consider the particular view defended by Hans Jonas. One who adopts this position would point out that in both World X and World Y, and identical loss occurs—the loss of the moral universe. Hence, with respect to this particular tragedy, these worlds are equally bad. One thus needs to find some other difference between the two worlds to assess their relative badness, and the most obvious place to look is how many people perish in each. Since more deaths occur in World X than World Y, someone who accepts Jonas’ position might claim that, in fact, the scenario of World X is worse. Consequently, they would concur with equivalence theorists about this, even while maintaining that the badness of what happens in World X goes above and beyond all the suffering and lives cut short by the catastrophe.

As for pro-extinctionists, most would also identify World X as worse, because the catastrophe causes more human suffering, and pro-extinctionists are generally opposed to human suffering. The silver lining of both scenarios, they would add, is that humanity stops existing in each.

If you’d like to support my work, you can do so via Patreon here, or via PayPal using this email address: phillip.torres@philos.uni-hannover.de. Financial support is greatly appreciated!

Additional Reading:

“The Ethics of Human Extinction,” Aeon, here.

“Against Longtermism,” Aeon, here.

“AI and the Threat of Human Extinction,” Salon, here.

“Nick Bostrom, Longtermism, and the Eternal Return of Eugenics,” Truthdig, here.

“The Bright Side of Extinction,” Truthdig, here.²⁴

“The Acronym Behind Our Wildest AI Dreams and Nightmares,” Truthdig, here.²⁵

---

1. This was made possible by the fact that I almost never read anything. Rather, I use a text-to-speech app to listen to books and papers at a very high speed. I mention this because my methodology might be useful to young scholars who find reading a large stack of books rather daunting. By listening and taking notes along the way, usually via speech-to-text or screenshots of the text being read by my app, I was able to devour a huge number of digitized books from Google Books and the Internet Archive. My notes for Part I of the book ended up being about 150,000 words (which I would then listen to again, iteratively, until I’d whittled down these notes to a manageable list of key ideas). Note also that I’m not naturally an auditory learner—I find lectures in realtime rather soporific! The rapidity of listening at such a fast pace actually grabs my attention more than listening at the normal rate. Hence, if you aren’t an auditory learner, this might still work for you.

2. A more complicated example comes from the ancient Greek atomists. As I write in the book (quoting a few paragraphs in what follows), the atomists held that everything in the universe is composed of “atoms” (literally, “uncuttable” or “indivisible”). Too small to see with the naked eye, they collide with each other while moving about the void, sometimes sticking together due to hooks and barbs on their surface. All macroscopic objects are the result of different configurations of atoms: one configuration yields a tree, another the moon, and yet another the human organism. Cosmologically, the atomists believed space and time to be infinite, like the number of atoms, and consequently an endless procession of worlds, or kosmoi, are formed through the random interaction of these particles. As Hippolytus of Rome describes the idea in his Refutation of All Heresies, Democritus, who founded the atomist school along with his teacher Leucippus, maintains that

in some [kosmoi] there is neither sun nor moon, while in others that they are larger than with us, and with others more numerous. And that [some] attain their full size, while others dwindle away and that in one quarter they are coming into existence, whilst in another they are failing; and that they are destroyed by clashing one with another.

On this view, the ultimate destiny of all kosmoi is complete dissolution. Hence, it is only a matter of time before our own world disappears and, along with it, the human race. Although I am not aware of any ancient atomists elaborating on this idea, total human extinction is a straightforward implication of their cosmological theory. However, this theory also implies that another world exactly like ours will eventually arise somewhere within the infinite corridors of space and time. What makes this view unique is that the growth and collapse of our world is not part of a serial sequence of events—that is to say, it is not our particular kosmos that perishes and reappears, as with Xenophanes, but rather different kosmoi arising and collapsing throughout the void. Consequently, there is a sense in which the atomists’ view implies that our species is not indestructible, since our lineage here on Earth will eventually cease to exist forever, although from a cosmic perspective, “humanity” may indeed be ineradicable, as creatures just like us will always exist.

3. Nonetheless, I show in the book (chapter 8) that a version of one of the central components of the Great Chain—a “spatialized” interpretation of the principle of plenitude—persisted for another century, into the early 1900s. When combined with a Copernican model of the universe, it implied that there is an infinite or near-infinite number of other “worlds” (solar systems) out there, complete with their own intelligent beings. Consequently, there were many authors who argued that our own world could be completely annihilated, yet in the grandness of the cosmos, “humanity” would persist. This “plurality of worlds” view was, surprising as it may seem to modern readers, the consensus view among educated people: just about everyone believed that the universe is overflowing with extraterrestrial intelligences. At first glance, then, it may appear that these writers were referencing human extinction in talking about the annihilation of our world and, with it, humanity, but in fact they were, in most cases, making a point about extirpation, whereby a population of some species disappears without that species itself dying out.

4. Note that some physicists did not believe that the heat death would occur because they thought the universe is infinite. However, they did believe that Earth itself would become uninhabitable as the sun burns through its reservoir of hydrogen, and hence that humanity’s days are numbered. In the book, I call this more localized eschatology the “solar death,” in contrast to the “heat death.”

5. A search through the archive of digitized texts from several centuries ago suggests, prima facie, that some people did worry about human extinction. However, this is misleading, because the term “human extinction” was used to mean the death of individuals before it commonly referred to the death of humanity itself. The same goes for terms like “human annihilation,” which was also sometimes a reference to a theological view called annihilationism, whereby the souls of unbelievers are simply annihilated after the Last Judgement rather than cast into hell forever. See appendix 1 of the book for discussion.

6. Although the mood took hold mostly among the educated elite, the bleak implications of the Second Law were popularized among the general public by novels like Camille Flammarion’s 1893 book La Fin du Monde (published in English the following year) and H. G. Wells’ 1895 The Time Machine.

7. This utilitarian idea is what motivated John Leslie’s 1996 book The End of the World, as well as subsequent publications by Milan Ćirković and Nick Bostrom. However, another key idea that motivated the futurological pivot was transhumanism, which both Ćirković and Bostrom subscribed to. For utilitarians, what awaits humanity if we avoid extinction—or, more generally, an “existential” catastrophe—is a posthuman paradise, a utopian world full of immortality, superintelligence, and “surpassing bliss and delight.” Kurzweil held a very similar view, although emphasizing the technological “Singularity,” which he believed would lead us to colonize space and, in doing this, enable the universe to “wake up.” Nonetheless, from both utilitarian and transhumanist perspectives, the value of the future could be enormous. This is why compiling an exhaustive list of every possible kill mechanism, however improbable or speculative, is of paramount moral importance.

8. This scenario makes the most sense if we become a posthuman species of some sort, since the far future may be much less hospitable to biological beings than, say, wholly artificial beings. Hence, a broader definition of “humanity” that includes artificial beings is especially relevant here.

9. Bostrom gestures at this type of extinction scenario in asking us to imagine a future “in which machine intelligence replaces biological intelligence but the machines are constructed in such a way that they lack consciousness (in the sense of phenomenal experience) … The future might then be very wealthy and capable, yet in a relevant sense uninhabited: There would (arguably) be no morally relevant beings there to enjoy the wealth.” In other words, the future would be uninhabited by anything we might call “humanity,” and hence normative extinction will have occurred.

10. An example is phyletic extinction. Transhumanists would argue that final extinction would be very bad, since it would preclude the realization of a posthuman utopia. However, if Homo sapiens were to undergo phyletic extinction by radically “enhancing” itself to become a new posthuman species, that would be very good—a major step toward realizing this utopia.

11. A note for philosophers: as this suggests, there are both deontic and evaluative interpretations of this view. The same goes for the further-loss and pro-extinctionist views discussed momentarily.

12. To borrow a line from Jonathan Schell, who we will discuss shortly: “Although extinction might appear to be the largest misfortune that mankind could ever suffer, it doesn’t seem to happen to anybody.” The reason is that “we, the living, will not suffer it; we will be dead. Nor will the unborn shed any tears over their lost chance to exist; to do so they would have to exist already.”

13. To be clear, this applies just as much to a parallel case in which, rather than a violent catastrophe, there are 10 billion people in each world who voluntarily decide not to have children. Since the details of Going Extinct are only part of the equation for further-loss theorists, they would see 10 billion people refusing to procreate in World B as wrong, even if they believe that 10 billion people remaining childless in World A is just fine. In World A, humanity persists, while in World B, it doesn’t—and that’s morally important, they would argue.

14. Note that some further-loss theorists might only care about final extinction, not normative extinction. An example is Larry Page, the cofounder of Google. He seems to believe that it doesn’t matter whether our successors count as human, or even whether they carry on our “values.” Machines replacing humans is simply the next step in cosmic evolution. Robin Hanson appears to hold a similar view. However, if they were to adopt Bostrom’s definition of “humanity,” then normative extinction might still matter to them, as they envision these future beings as intelligent or superintelligent. How one defines “humanity” matters.

15. I say “almost certainly” because, theoretically speaking, demographic extinction might not entail final extinction if it were to happen in the near future. An alien civilization could discover Earth and resurrect us, or our universe could be a giant simulation that the simulators restart so that we exist once more. These are fun to think about, but not realistic. If the human population falls to zero in the next few decades, this would—with a probability close to 1—mark a complete and final end to the entire human story.

16. Why? Because colonizing space will be much easier for digital creatures than biological ones. See my forthcoming chapter “Colonization, Consciousness, and Longtermism” in the book Outer Space and Philosophy.

17. An example is David Benatar, in his book Better Never to Have Been. The no-ordinary-catastrophe thesis is what motivates his notion of “phased extinction.”

18. Note that Schopenhauer himself did not explicitly endorse pro-extinctionism.

19. A variation of this argument focuses not on attaining specific goals, but on continuing the process of scientific, artistic, philosophical, and so on, development. I call this the “argument from persistent progress.” Although Bennett is widely interpreted as defending the argument from unfinished business, he clarified to me in an email that he intended only to defend the idea of “persistent progress.”

20. This finds expression in the following statement from Peter Singer, Nick Beckstead, and Matthew Wage:

One very bad thing about human extinction would be that billions of people would likely die painful deaths. But in our view, this is, by far, not the worst thing about human extinction. The worst thing about human extinction is that there would be no future generations.

We believe that future generations matter just as much as our generation does. Since there could be so many generations in our future, the value of all those generations together greatly exceeds the value of the current generation.

21. I am referring to an old email written by Bostrom in which he uses the N-word and declares that “Blacks are more stupid than whites.” Timnit Gebru and I first discovered this email in December, 2022. Bostrom then issued an “apology” in which he denounced his use of a racial slur but did not walk back his claim about race and “intelligence.”

22. Note that the word “longtermism” wasn’t coined until 2017. The idea predates this, however.

23. If our extinction were instantaneous, I would still consider this very bad, because I accept the anti-Epicurean view that death can harm the one who dies by depriving them of good experiences, fulfilled desires, and so on, which they could have otherwise had. The book goes into some detail about this view.

24. Once again, I regret giving David Benatar so much air-time in my publications, including this article, given his history of deeply problematic views on race and disability, which I only became aware of recently. Around 2016, Benatar was accused by a student of racism, ableism, and sexism. He has vocally opposed affirmative action in post-apartheid South Africa, published a grievance-filled article about social justice activists for the rightwing outlet Quillette, and released a book titled The Second Sexism, which argues that men and boys face discrimination in society. In the 2006 book that I reference about antinatalism, he also makes a number of ableist claims that I’d missed when reading it some years ago.

25. See also “Eugenics and the Promise of Utopia through AGI,” by Timnit Gebru, here.