What We Owe the Future


By William MacAskill

Formats and Prices




$24.99 CAD



  1. Trade Paperback $19.99 $24.99 CAD
  2. ebook $14.99 $19.99 CAD
  3. Hardcover $32.00 $40.00 CAD

This item is a preorder. Your payment method will be charged immediately, and the product is expected to ship on or around September 12, 2023. This date is subject to change due to shipping delays beyond our control.

In this instant New York Times bestseller, a renowned philosopher puts forth the case for longtermism 

The fate of the world – and the future – is in our hands. Now with a new foreword, What We Owe the Future argues for longtermism: that positively influencing the distant future is our time’s key moral priority. It’s not enough to reverse climate change or avert a pandemic. We must ensure that civilization would rebound if it collapsed; counter the end of moral progress; and prepare for a planet where the smartest beings are digital. 

If we make wise choices now, our grandchildren will thrive, knowing we did everything we could to give them a world full of justice, hope and beauty. 

“To take these ideas seriously is a truly radical endeavor — one with the power to change the world and even your life.”—Ezra Klein, New York Times 

“An intellectually thrilling exploration of moral philosophy and human history in the hands of a very skilled thinker and clear writer.”—Kevin J. Delaney, The Charter 





Imagine living, in order of birth, through the life of every human being who has ever lived.1 Your first life begins about three hundred thousand years ago in Africa.2 After living that life and dying, you travel back in time and are reincarnated as the second-ever person, born slightly later than the first. Once that second person dies, you are reincarnated as the third person, then the fourth, and so on. One hundred billion lives later,3 you become the youngest person alive today. Your “life” consists of all of these lifetimes, lived consecutively.

Your experience of history is very different from what is depicted in most textbooks. Famous figures like Cleopatra or Napoleon account for a tiny fraction of your experience. The substance of your life is instead composed of ordinary lives, filled with everyday realities—eating, working, and socialising; laughing, worrying, and praying.

Your life lasts for almost four trillion years in total. For a tenth of that time, you’re a hunter-gatherer, and for 60 percent you’re an agriculturalist.4 You spend a full 20 percent of your life raising children, a further 20 percent farming, and almost 2 percent taking part in religious rituals. For over 1 percent of your life you are afflicted with malaria or smallpox. You spend 1.5 billion years having sex and 250 million giving birth. You drink forty-four trillion cups of coffee.5

You experience cruelty and kindness from both sides. As a colonizer, you invade new lands; as the colonized, you suffer your lands taken from you. You feel the rage of the abuser and the pain of the abused. For about 10 percent of your life you are a slaveholder; for about the same length of time, you are enslaved.6

You experience, firsthand, just how unusual the modern era is. Because of dramatic population growth, a full third of your life comes after AD 1200 and a quarter after 1750. At that point, technology and society begin to change far faster than ever before. You invent steam engines, factories, and electricity. You live through revolutions in science, the most deadly wars in history,7 and dramatic environmental destruction. Each life lasts longer, and you enjoy luxuries that you could not sample even in your past lives as kings and queens. You spend 150 years in space and one week walking on the moon. Fifteen percent of your experience is of people alive today.8

That’s your life so far—from the birth of Homo sapiens until the present. But now imagine that you live all future lives, too. Your life, we hope, would be just beginning. Even if humanity lasts only as long as the typical mammalian species (one million years), and even if the world population falls to a tenth of its current size, 99.5 percent of your life would still be ahead of you.9 On the scale of a typical human life, you in the present would be just five months old. And if humanity survived longer than a typical mammalian species—for the hundreds of millions of years remaining until the earth is no longer habitable, or the tens of trillions remaining until the last stars burn out—your four trillion years of life would be like the first blinking seconds out of the womb.10 The future is big.

If you knew you were going to live all these future lives, what would you hope we do in the present? How much carbon dioxide would you want us to emit into the atmosphere? How much would you want us to invest in research and education? How careful would you want us to be with new technologies that could destroy or permanently derail your future? How much attention would you want us to give to the impact of today’s actions on the long term?

I present this thought experiment because morality, in central part, is about putting ourselves in others’ shoes and treating their interests as we do our own. When we do this at the full scale of human history, the future—where almost everyone lives and where almost all potential for joy and misery lies—comes to the fore.

This book is about longtermism: the idea that positively influencing the longterm future is a key moral priority of our time.11 Longtermism is about taking seriously just how big the future could be and how high the stakes are in shaping it. If humanity survives to even a fraction of its potential life span, then, strange as it may seem, we are the ancients: we live at the very beginning of history, in the most distant past. What we do now will affect untold numbers of future people. We need to act wisely.

It took me a long time to come around to longtermism. It’s hard for an abstract ideal, focused on generations of people whom we will never meet, to motivate us as more salient problems do. In high school, I worked for organisations that took care of the elderly and disabled. As an undergraduate who was concerned about global poverty, I volunteered at a children’s polio rehabilitation centre in Ethiopia. When starting graduate work, I tried to figure out how people could help one another more effectively. I committed to donating at least 10 percent of my income to charity, and I cofounded an organization, Giving What We Can, to encourage others to do the same.12

These activities had a tangible impact. By contrast, the thought of trying to improve the lives of unknown future people initially left me cold. When a colleague presented me with arguments for taking the long term seriously, my immediate reaction was glib dismissal. There are real problems in the world facing real people, I thought, problems like extreme poverty, lack of education, and death from easily preventable diseases. That’s where we should focus. Sci-fi-seeming speculations about what might or might not impact the future seemed like a distraction.

But the arguments for longtermism exerted a persistent force on my mind. These arguments were based on simple ideas: that, impartially considered, future people should count for no less, morally, than the present generation; that there may be a huge number of future people; that life, for them, could be extraordinarily good or inordinately bad; and that we really can make a difference to the world they inhabit.

The most important sticking point for me was practical: Even if we should care about the longterm future, what can we do? But as I learned more about the potentially history-shaping events that could occur in the near future, I took more seriously the idea that we might soon be approaching a critical juncture in the human story. Technological development is creating new threats and opportunities for humanity, putting the lives of future generations on the line.

I now believe the world’s long-run fate depends in part on the choices we make in our lifetimes. The future could be wonderful: we could create a flourishing and long-lasting society, where everyone’s lives are better than the very best lives today. Or the future could be terrible, falling to authoritarians who use surveillance and AI to lock in their ideology for all time, or even to AI systems that seek to gain power rather than promote a thriving society. Or there could be no future at all: we could kill ourselves off with biological weapons or wage an all-out nuclear war that causes civilisation to collapse and never recover.

There are things we can do to steer the future onto a better course. We can increase the chance of a wonderful future by improving the values that guide society and by carefully navigating the development of AI. We can ensure we get a future at all by preventing the creation or use of new weapons of mass destruction and by maintaining peace between the world’s great powers. These are challenging issues, but what we do about them makes a real difference.

So I shifted my priorities. Still unsure about the foundations and implications of longtermism, I switched my research focus and cofounded two organisations to investigate these issues further: the Global Priorities Institute at Oxford University, and the Forethought Foundation. Drawing on what I have learned, I have tried to write the case for longtermism that would have convinced me a decade ago.

To illustrate the claims in this book, I rely on three primary metaphors throughout. The first is of humanity as an imprudent teenager. Most of a teenager’s life is still ahead of them, and their decisions can have lifelong impacts. In choosing how much to study, what career to pursue, or which risks are too risky, they should think not just about short-term thrills but also about the whole course of the life ahead of them.

The second is of history as molten glass. At present, society is still malleable and can be blown into many shapes. But at some point, the glass might cool, set, and become much harder to change. The resulting shape could be beautiful or deformed, or the glass could shatter altogether, depending on what happens while the glass is still hot.

The third metaphor is of the path towards longterm impact as a risky expedition into uncharted terrain. In trying to make the future better, we don’t know exactly what threats we will face or even exactly where we are trying to go; but, nonetheless, we can prepare ourselves. We can scout out the landscape ahead of us, ensure the expedition is well resourced and well coordinated, and, despite uncertainty, guard against those threats we are aware of.

This book’s scope is broad. Not only am I arguing for longtermism; I’m also trying to work out its implications. I’ve therefore relied heavily on an extensive team of consultants and research assistants. Whenever I’ve stepped outside of moral philosophy, my area of expertise, domain experts have advised me from start to end. This book is therefore not really “mine”: it has been a team effort. In total, this book represents over a decade’s worth of full-time work, almost two years of which was spent fact-checking.

For those who want to dig deeper into some of my claims, I have compiled extensive supplementary materials, including special reports I commissioned as background research, and made them available at whatweowethefuture.com. Despite the work done so far, I believe we have only scratched the surface of longtermism and its implications; there is much still to learn.

If I’m right, then we face a huge responsibility. Relative to everyone who could come after us, we are a tiny minority. Yet we hold the entire future in our hands. Everyday ethics rarely grapples with such a scale. We need to build a moral worldview that takes seriously what’s at stake.

By choosing wisely, we can be pivotal in putting humanity on the right course. And if we do, our great-great-grandchildren will look back and thank us, knowing that we did everything we could to give them a world that is just and beautiful.



The Case for Longtermism

The Silent Billions

Future people count. There could be a lot of them. We can make their lives go better.

This is the case for longtermism in a nutshell. The premises are simple, and I don’t think they’re particularly controversial. Yet taking them seriously amounts to a moral revolution—one with far-reaching implications for how activists, researchers, policy makers, and indeed all of us should think and act.

Future people count, but we rarely count them. They cannot vote or lobby or run for public office, so politicians have scant incentive to think about them. They can’t bargain or trade with us, so they have little representation in the market. And they can’t make their views heard directly: they can’t tweet, or write articles in newspapers, or march in the streets. They are utterly disenfranchised.

Previous social movements, such as those for civil rights and women’s suffrage, have often sought to give greater recognition and influence to disempowered members of society. I see longtermism as an extension of these ideals. Though we cannot give genuine political power to future people, we can at least give consideration to them. By abandoning the tyranny of the present over the future, we can act as trustees—helping to create a flourishing world for generations to come. This is of the utmost importance. Let me explain why.

Future People Count

The idea that future people count is common sense. Future people, after all, are people. They will exist. They will have hopes and joys and pains and regrets, just like the rest of us. They just don’t exist yet.

To see how intuitive this is, suppose that, while hiking, I drop a glass bottle on the trail and it shatters. And suppose that if I don’t clean it up, later a child will cut herself badly on the shards.1 In deciding whether to clean it up, does it matter when the child will cut herself? Should I care whether it’s a week, or a decade, or a century from now? No. Harm is harm, whenever it occurs.

Or suppose that a plague is going to infect a town and kill thousands. You can stop it. Before acting, do you need to know when the outbreak will occur? Does that matter, just on its own? No. The pain and death at stake are worthy of concern regardless.

The same holds for good things. Think of something you love in your own life; maybe it’s music or sports. And now imagine someone else who loves something in their life just as much. Does the value of their joy disappear if they live in the future? Suppose you can give them tickets to see their favourite band or the football team they support. To decide whether to give them, do you need to know the delivery date?

Imagine what future people would think, looking back at us debating such questions. They would see some of us arguing that future people don’t matter. But they look down at their hands; they look around at their lives. What is different? What is less real? Which side of the debate will seem more clear-headed and obvious? Which more myopic and parochial?

Distance in time is like distance in space. People matter even if they live thousands of miles away. Likewise, they matter even if they live thousands of years hence. In both cases, it’s easy to mistake distance for unreality, to treat the limits of what we can see as the limits of the world. But just as the world does not stop at our doorstep or our country’s borders, neither does it stop with our generation, or the next.

These ideas are common sense. A popular proverb says, “A society grows great when old men plant trees under whose shade they will never sit.”2 When we dispose of radioactive waste, we don’t say, “Who cares if this poisons people centuries from now?” Similarly, few of us who care about climate change or pollution do so solely for the sake of people alive today. We build museums and parks and bridges that we hope will last for generations; we invest in schools and longterm scientific projects; we preserve paintings, traditions, languages; we protect beautiful places. In many cases, we don’t draw clear lines between our concerns for the present and the future—both are in play.

Concern for future generations is common sense across diverse intellectual traditions. The Gayanashagowa, the centuries-old oral constitution of the Iroquois Confederacy, has a particularly clear statement. It exhorts the Lords of the Confederacy to “have always in view not only the present but also the coming generations.”3 Oren Lyons, a faithkeeper for the Onondaga and Seneca nations of the Iroquois Confederacy, phrases this in terms of a “seventh-generation” principle, saying, “We… make every decision that we make relate to the welfare and well-being of the seventh generation to come.… We consider: will this be to the benefit of the seventh generation?”4

However, even if you grant that future people count, there’s still a question of how much weight to give their interests. Are there reasons to care more about people alive today?

Two reasons stand out to me. The first is partiality. We often have stronger special relationships with people in the present, like family, friends, and fellow citizens, than with people in the future. It’s common sense that you can and should give extra weight to your near and dear.

The second reason is reciprocity. Unless you live as a recluse in the wilderness, the actions of an enormous number of people—teachers, shopkeepers, engineers, and indeed all taxpayers—directly benefit you and have done so throughout your life. We typically think that if someone has benefited you, that gives you a reason to repay them. But future people don’t benefit you the way others in your generation do.5

Special relationships and reciprocity are important. But they do not change the upshot of my argument. I’m not claiming that the interests of present and future people should always and everywhere be given equal weight. I’m just claiming that future people matter significantly. Just as caring more about our children doesn’t mean ignoring the interests of strangers, caring more about our contemporaries doesn’t mean ignoring the interests of our descendants.

To illustrate, suppose that one day we discover Atlantis, a vast civilisation at the bottom of the sea. We realise that many of our activities affect Atlantis. When we dump waste into the oceans, we poison its citizens; when a ship sinks, they recycle it for scrap metal and other parts. We would have no special relationships with the Atlanteans, nor would we owe them repayment for benefits they had bestowed on us. But we should still give serious consideration to how our actions affect them.

The future is like Atlantis. It, too, is a vast, undiscovered country;6 and whether that country thrives or falters depends, in significant part, on what we do today.

The Future Is Big

It’s common sense that future people count. So, too, is the idea that, morally, the numbers matter. If you can save one person or ten from dying in a fire, then, all else being equal, you should save ten; if you can cure a hundred people or a thousand of a disease, you should cure a thousand. This matters, because the number of future people could be huge.

To see this, consider the long-run history of humanity. There have been members of the genus Homo on Earth for over 2.5 million years.7 Our species, Homo sapiens, evolved around three hundred thousand years ago. Agriculture started just twelve thousand years ago, the first cities formed only six thousand years ago, the industrial era began around 250 years ago, and all the changes that have happened since then—transitioning from horse-drawn carts to space travel, leeches to heart transplants, mechanical calculators to supercomputers—occurred over the course of just three human lifetimes.8

Figure 1.1. The history of Homo sapiens.

Figure 1.2. The potential future of civilisation, if humans survive as long as the average mammalian species.

How long will our species last? Of course, we don’t know. But we can make informative estimates that take our uncertainty into account, including our uncertainty about whether we’ll cause our own demise.

To illustrate the potential scale of the future, suppose that we only last as long as the typical mammalian species—that is, around one million years.9 Also assume that our population continues at its current size. In that case, there would be eighty trillion people yet to come; future people would outnumber us ten thousand to one.

Of course, we must consider the whole range of ways the future could go. Our life span as a species could be much shorter than that of other mammals if we cause our own extinction. But it could also be much longer. Unlike other mammals, we have sophisticated tools that help us adapt to varied environments; abstract reasoning, which allows us to make complex, long-term plans in response to novel circumstances; and a shared culture that allows us to function in groups of millions. These help us avoid threats of extinction that other mammals can’t.10

This has an asymmetric impact on humanity’s life expectancy. The future of civilisation could be very short, ending within a few centuries. But it could also be extremely long. The earth will remain habitable for hundreds of millions of years. If we survive that long, with the same population per century as now, there will be a million future people for every person alive today. And if humanity ultimately takes to the stars, the timescales become literally astronomical. The sun will keep burning for five billion years; the last conventional star formations will occur in over a trillion years; and, due to a small but steady stream of collisions between brown dwarfs, a few stars will still shine a million trillion years from now.11

Figure 1.3. The potential future of civilisation if it survives until the earth becomes uninhabitable for humans due to the sun’s increasing brightness. There is considerable uncertainty as to the length of this window, with estimates ranging from 500 million to 1.3 billion years.

The real possibility that civilisation will last such a long time gives humanity an enormous life expectancy. A 10 percent chance of surviving five hundred million years until the earth is no longer habitable gives us a life expectancy of over fifty million years; a 1 percent chance of surviving until the last conventional star formations give us a life expectancy of over ten billion years.12

Ultimately, we shouldn’t care just about humanity’s life expectancy but also about how many people there will be. So we must ask: How many people in the future will be alive at any one time?

Future populations might be much smaller or much larger than they are today. But if the future population is smaller, it can be smaller by eight billion at most—the size of today’s population. In contrast, if the future population is bigger, it could be much bigger. The current global population is already over a thousand times larger than it was in the hunter-gatherer era. If global population density increased to that of the Netherlands—an agricultural net exporter—there would be seventy billion people alive at any one time.13 This might seem fantastical, but a global population of eight billion would have seemed fantastical to a prehistoric hunter-gatherer or an early agriculturalist.

Population size could get dramatically larger again if we one day take to the stars. Our sun produces billions of times as much sunlight as lands on Earth, there are tens of billions of other stars across our galaxy, and billions of galaxies are accessible to us.14 There might therefore be vastly more people in the distant future than there are today.

Just how many? Precise estimates are neither possible nor necessary. On any reasonable accounting, the number is immense.

To see this, look at the following diagram. Each figure represents ten billion people. So far, roughly one hundred billion people have ever lived. These past people are represented as ten figures. The present generation consists of almost eight billion people, which I’ll round up to ten billion and represent with a single figure:

Next, we’ll represent the future. Let’s just consider the scenario where we stay at current population levels and live on Earth for five hundred million years. These are all the future people:

Represented visually, we begin to see how many lives are at stake. But I cut the diagram short. The full version would fill twenty thousand pages—saturating this book a hundred times over. Each figure would represent ten billion lives, and each of those lives could be flourishing or wretched.

Earlier, I suggested that humanity today is like an imprudent teenager: most of our life is ahead of us, and decisions that impact the rest of that life are of colossal importance. But, really, this analogy understates my case. A teenager knows approximately how long she can expect to live. But we do not know humanity’s life expectancy. We are more like a teenager who, for all she knows, might accidentally cause her own death in the next few months but also might live for a thousand years. If you were in such a situation, would you think seriously about the long life that might be ahead of you, or would you ignore it?

The sheer size of the future can be dizzying. Typically, “longterm” thinking involves attention to years or decades at most. But even with a low estimate of humanity’s life expectancy, this is like a teenager believing that longterm thinking means considering tomorrow but not the day after.

Despite how overwhelming thoughts of our future can be, if we truly care about the interests of future generations—if we recognize that they are real people, capable of happiness and suffering just like us—then we have a duty to consider how we might impact the world they inhabit.

The Value of the Future

The future could be very big. It could also be very good—or very bad.


  • “This book will change your sense of how grand the sweep of human history could be, where you fit into it, and how much you could do to change it for the better. It's as simple, and as ambitious, as that.”—Ezra Klein, host of The Ezra Klein Show podcast
  • “An optimistic look at the future that moved me to tears.”
     —Joseph Gordon-Levitt, actor
  • What We Owe The Future makes the case for thinking seriously about the very long term. It gives a profoundly new perspective on human civilization and our place in it.”
     —Lydia Cacho, journalist and author of The Demons of Eden
  • What We Owe the Future is an intellectually thrilling exploration of moral philosophy and human history in the hands of a very skilled thinker and clear writer… Thought provoking.”—Charter
  • “Unapologetically optimistic and bracingly realistic, this is the most inspiring book on ‘ethical living’ I’ve ever read.”—The Guardian (UK)
  • “In focusing on the interests of future generations stretching into an indefinitely long future, MacAskill has thrust an important and neglected argument into the spotlight, while making it vivid and fun to read. He hopes this book will change the world, and it might.”—Financial Times (UK)
  • “Touchingly optimistic… With something to ponder on every page, a bracing exhortation to do right by the people of centuries to come.”

  • “MacAskill delivers a sweeping analysis of contemporary dangers that masterfully probes the intersections of technology, science, and politics, while offering fascinating glimpses into humanity’s possible futures. This urgent call to action will inspire and unnerve in equal measure.”—Publishers Weekly
  • What We Owe the Future is an instructive, intelligent book. It has a lot to teach us about history and the future, about neglected risks and moral myopia.”—Boston Review
  • “No living philosopher has had a greater impact upon my ethics than Will MacAskill. In What We Owe The Future, MacAskillhas transformed my thinking once again, by patiently dismantling the lazy intuitions that rendered me morally blind to the interests of future generations. This is an altogether thrilling and necessary book.”
     —Sam Harris, five-time New York Times bestselling author and host of the Making Sense podcast
  • "An exciting new book."—Tyler Cowen, Marginal Revolution
  • “An extraordinary book. I've never read something so deep and fundamental, and so accessible at the same time . . . The publication of this book is a monumental event. William MacAskill is one of the most important philosophers alive today, and this is his magnum opus.”—Rutger Bregman, Dutch historian and author of Utopia for Realists
  • “This is a book of great daring, clarity, insight and imagination. To be simultaneously so realistic and so optimistic, and always so damned readable … that is a miracle for which MacAskill should be greatly applauded.”
     —Stephen Fry, actor
  • "There are moments when we can change outcomes easily, but if we don't bend those curves right then, we can lock in enormous long-term damage. This fascinating book makes us think relentlessly and usefully about such pivot points; few prods could be more important.”
     —Bill McKibben, environmentalist and author of The End of Nature
  • "Many books promise a new ‘big idea’, but few deliver one as brilliant as MacAskill’s in What We Owe The FutureA fascinating, profound read."
     —Julia Galef, author of The Scout Mindset
  • “Warning: This book may radically upgrade your ethics and expand your compassion. What We Owe The Future is an inspiring roadmap to how we can try to improve the lives of the billions and trillions sentient beings yet to come. It’s perhaps our greatest moral duty. So please do yourself – and your grandchildren's grandchildren's grandchildren – a favor and read this book.”
     —AJ Jacobs, editor at large of Esquire Magazine
  • “This mind-bending, eon-hurtling, visionary, masterful book raises questions that are among the most crucial we face as a species. MacAskill makes a moral case for the future that is urgent, clear, and utterly convincing.”
     —Larissa MacFarquhar, staff writer for The New Yorker and author of Strangers Drowning
  • “To assess what really matters it always helps to zoom out, and Will MacAskill is probably the world’s best zoom-outer. What We Owe The Future brilliantly shows us the biggest picture of all and persuasively reminds us of the vast impact we can all have.” 

    Tim Urban, co-founder of Wait but Why
  • “I expected William MacAskill to write a forceful and persuasive argument for caring more about future people and this book did not disappoint. But it’s so much more—What We Owe The Future is an engaged and deeply original exploration of questions ranging from the contingency of moral progress, to the perils of AI, to the very nature of a happy and fulfilled life. It’s an important, stimulating, and delightful book.”

    Paul Bloom

On Sale
Sep 12, 2023
Page Count
368 pages
Basic Books