Nonfiction Books » History Books » World History

The best books on Big History

recommended by Toby Ord

The Precipice: Existential Risk and the Future of Humanity by Toby Ord

The Precipice: Existential Risk and the Future of Humanity
by Toby Ord


'Big history' looks at history on the timescale of the Earth and the universe, rather than just the short period of time that humanity has been around. Here, Toby Ord, a moral philosopher at Oxford University's Future of Humanity Institute, recommends books to get a handle on it, and explains why now is a critical time for Homo sapiens.

Interview by Caspar Henderson

The Precipice: Existential Risk and the Future of Humanity by Toby Ord

The Precipice: Existential Risk and the Future of Humanity
by Toby Ord

Buy all books

What is ‘big history’ and why does it matter?

Big history is an attempt to understand the course of events in the universe at an extremely large scale. Most history is at the biographical scale, looking at periods of up to a single lifetime. At that scale, history is very contingent — things could easily have gone otherwise. It may seem increasingly difficult to say things about longer timescales, but on closer examination, it appears to get easier — just as it can be almost impossible to predict whether a particular atom will decay within the next half-life, but easy to predict that it will decay after a thousand half-lives. Or, for another example, it is hard to predict what will happen to the stock market this week, but much easier to predict it will rise substantially over the next century.

Big history asks about trends over periods ranging from centuries all the way up to the entire 10,000-year period of civilisation, or the entire 200,000 years of Homo sapiens, or even the 13.8-billion-year history of the universe (where the patterns of development include those of evolution and non-biological processes). Of course, many important things disappear from view at such scales, but there are other key features that come into sharper relief: those concerning the nature of humanity, whether things are getting better or worse over the centuries, and where our greatest challenges lie.

Tell me about your first choice, Maps of Time by David Christian.

This is the big book on big history. And it is a masterpiece. David Christian takes you from the big bang through to the present day, tracing our best understanding of the way events develop over time. He does this through a series of telescoping time periods, from a lifeless universe to the rise of life, humans, civilisation and ultimately industry. He explains the big picture of each period, with a good mixture of rigour and clarity.

Get the weekly Five Books newsletter

And why should one read Origins by Lewis Dartnell?

Dartnell’s focus is on how the Earth shaped human history. It is a fascinating look into how much of the apparently contingent developments over the last 200,000 years were in fact governed by Earth systems and geography. What was so special about the rift valley where humanity began? Why did so many civilisations arise near tectonic plate boundaries? Why does the US political map show a shadow of the old continental coastline during the Cretaceous era? It helps make sense of many different aspects of the rise of humanity all over the world.

What about The Five Ages of the Universe by Fred Adams and Gregory Laughlin?

The Five Ages of the Universe zooms out further still — considering not just the entire history of the universe, but its entire future too. It breaks this down into five periods of increasing length. From the big bang to the first stars 100,000 years later is the Primordial Era. We now live in the Stelliferous Era which is characterised by billions upon billions of shining stars and the vast energy they output. But in 100 trillion years, these stars will have burnt out and the Degenerate Era will be characterised by what happens to their dying embers. And in about a trillion trillion trillion years, even these will be gone and we will only be left with black holes. Then, after 10 to the power of 100 years, even the black holes will evaporate, leaving an everlasting Dark Era.

Or at least that is the current best understanding in astrophysics. Adams and Laughlin paint a rigorous yet deeply engaging picture of the universe unfolding through these very alien eras and, in each one, they sketch some ideas about how life might be able to continue, or even thrive, as the universe ever-so-slowly winds down.

Quite a few people may have heard Carl Sagan’s phrase the ‘pale blue dot’ without knowing much more than that it is an image of the Earth from far away. How does the book speak to you? 

Pale Blue Dot is a contemplation on humanity, and our future. It asks who we are and where we came from, in order to understand where we are going. In particular, it examines the possibilities of space travel within our solar system and to other stars over the next few centuries. The thing I found most compelling about it was how it described the science of these endeavours in such evocative — indeed poetic — ways. I hadn’t realised it was even possible to write like this, combining clarity, accuracy and beauty, and it made a great impression on me.

You recently posted Earth Restored on your website — a selection of photographs of the Earth from space taken during the Apollo programme which you have restored yourself. What was that like to do, and how does a project like that fit with your values and goals?  

It was a singular experience to sit in the dark, evening after evening, and gaze in wonder at these images — searching for old favourites and unknown gems; bringing out their inner beauty. It was a lot of work too, but good work, and a real treat to get to play some small part in producing the best images of the Earth we have.

When astronauts see the Earth against the black of space, many feel a profound change in perspective that continues even when they return — something to do with seeing the unity of a world unmarred by borders, as well as the fragility and uniqueness of our home amidst an uncaring universe. Known as the ‘Overview Effect’, this has led many to a perspective that places humanity at the centre of their view, instead of their own national conflicts. Even without leaving the surface, I think contemplating these images can give something of that sense of perspective and inspiration to many of us — it certainly did to me.
The late Michael Collins, who flew the Apollo 11 command module in 1969, put it well:

“I really believe that if the political leaders of the world could see their planet from a distance of, let’s say 100,000 miles, their outlook would be fundamentally changed. The all-important border would be invisible, that noisy argument suddenly silenced. The tiny globe would continue to turn, serenely ignoring its subdivisions, presenting a unified facade that would cry out for unified understanding, for homogeneous treatment. The earth must become as it appears: blue and white, not capitalist or communist; blue and white, not rich or poor; blue and white, not envious or envied.”

Please tell us about your final choice, Diaspora by Greg Egan. 

It is a masterwork of science fiction, and the deepest account I’ve seen of how much the human condition could change. The book opens almost 1,000 years into the future. But at some point, much closer to the present day, humanity had worked out how to create digital minds, living in virtual worlds. And the book is primarily an exploration of how profoundly such a development would change things. Many age-old challenges of social arrangement would become moot. For instance, the people of this future are effectively immortal and cannot come to any bodily harm unless they will it. So in these virtual worlds, violent crime is not against the law, but against the laws of physics. But many new challenges appear, such as finding meaning in these lives of ease, or keeping a coherent self-concept when living for millions of subjective years. Unlike the other books here, it is not a history, or even a prediction. But what is so interesting is that it is a fascinating sketch of how utterly strange and new humanity’s long-term future could be.

What is ‘the precipice’ in the title of your book, The Precipice: Existential Risk and the Future of Humanity?

Humanity has existed for about 200,000 years, a time that has seen a remarkable ascent in our power to transform the world. Very recently, in the 20th century, our escalating power finally reached a point where we could make weapons of such devastation that they could threaten our continued existence. We still live under the shadow of nuclear weapons, and have added new risks such as catastrophic climate change. And the coming hundred years will see additional risks, such as those of engineered pandemics and unaligned artificial intelligence.

It is as if on humanity’s long journey, we have reached a high mountain pass where the only way forward is along a narrow ledge on the cliffside, above a sheer precipice. We don’t know exactly what the chances of falling are, but we can tell that this is the most dangerous moment of our journey so far. Our entire future will depend on whether we can make it through this time.

I’d like to better understand the nature and importance of existential risks as you see them.  A hypothetical from Derek Parfit may help here. He asked us to consider three scenarios: (1) world peace; (2) a nuclear war that kills 99% of the world’s population; and (3) a nuclear war that kills 100% of the world’s population. He then asked us to consider where the greatest moral difference lay – between (1) and (2) or between (2) and (3). He guessed that most people would say it is between (1) and (2).  But he disagreed, arguing that the difference between (2) and (3) is very much greater than between (1) and (2). You studied with Parfit and I think you agree with his position.  Could you explain why?

What Parfit saw was that human extinction would destroy not only our present, but our entire future. We have survived for 10,000 generations and if we don’t destroy ourselves, we could survive for tens of thousands more. But we have got ourselves to a point where this entire future is at stake.

On page 167 of The Precipice you give your best estimates for the chance of an existential catastrophe in the next hundred years from a variety of causes, and say they add up to a total chance of around 1 in 6.  Could you say something about how you came to these estimates?

When writing the book, I thought hard on whether to give numbers at all, as they can easily suggest a false precision. But I decided it would be a disservice to the reader to have them read so far and then simply not tell them how large I thought the risks were. The numbers are ultimately my best guesses — my own degrees of belief that there will be an existential catastrophe of each type in the next hundred years, based on a decade of research and conversation with experts.

Support Five Books

Five Books interviews are expensive to produce. If you're enjoying this interview, please support us by .

I treat them as order-of-magnitude estimates, meaning that they are trying to be correct to within a factor of 10. In many cases such rough estimates would be useless, but note that my estimates of the risks range from 1 in 1,000,000 to 1 in 10, so even such rough estimates can help people understand which ballpark we are talking. And by putting a number on things, it also allows the reader to see that although I think the risk is very serious, I still think we are more likely than not to make it through the century.

You estimate that the greatest risk, at around 1 in 10, will come from “unaligned artificial intelligence.” But you write elsewhere  (p. 149) that “The case for existential risk from AI is clearly speculative. Indeed, it is the most speculative case for a major risk in this book.”  So how much confidence should we place in the estimate?

One way to understand the robustness of a probability estimate is to ask about how much disagreement there is among experts. Here, it is vast. Some think that the chance is extremely close to zero, while others think it is almost a foregone conclusion — something like a 90% chance. Thus the evidence around AI risk isn’t strong enough to force all reasonable people to a similar answer. You could think of my 1 in 10 as a hedge in this situation: something like the average among my peers.

The writer Jim Holt has argued that if we follow your argument in The Precipice we risk becoming “moral slaves” to the distant future — that the book “leads to a distorted picture of how we should distribute our present moral concerns, suggesting that we should be relatively less worried about real and ongoing developments that will gravely harm humanity without wiping it out completely, and relatively more worried about notional threats that, however unlikely, could conceivably result in human extinction.”  How do you respond?

I am indeed suggesting that existential risk is a key priority for our time. And I do think it is extremely important. I think Holt would agree that the loss of our entire future, of everything that we could ever accomplish, would be extremely bad. And when something is so bad, it can be important to work on it even when the chance of changing the outcome is smaller. But there is a question of how far this goes. How much more important is our future than our present? How small would the chances of saving the future need to be to warrant costly action? His real fear, as I understand it, is that it seems difficult to get off this train — to avoid concluding that protecting our future overwhelms the importance of all other things.

I’m sympathetic to this. But I don’t think the solution can be to thereby conclude that future lives and achievements must matter much less than our own. I think we are just in a very unusually weighty situation: a unique period for humanity where sorting out how to safeguard our future really is of paramount importance. It is thus like living through a crisis or emergency, where resolving that emergency can temporarily become a chief priority.

But I’m not sure how much depends on our disagreement. At the moment, humanity spends less on protecting its future from existential risk than it does on ice cream. And however we think of the value of the future, we can agree that we certainly need to start doing much more than this. The question of exactly where to stop can wait.

Do you see any encouraging signs?  What are some of the things that we, as individuals, can do?

There are many reasons why we have neglected existential risk. One of those is actually quite hopeful, which is that it is a very new challenge and it takes a long time for us to update our understanding of our moral situation. At the moment, there is a strong rise in the number of researchers looking at these questions and the number of young people who come to understand the threats and want to devote themselves to safeguarding humanity. The careers site ‘80,000 Hours’ has a vast wealth of advice for how to use your career (and this vast number of hours you will spend at work) to help safeguard our future. Even if it is too late to choose (or change) your career, it is never too late to pick up a book about existential risk to learn about the threats we face and why they matter, or to donate to an organisation such as Nuclear Threat Initiative who are trying their hardest to prevent the worst from happening.

Interview by Caspar Henderson

June 5, 2021

Five Books aims to keep its book recommendations and interviews up to date. If you are the interviewee and would like to update your choice of books (or even just what you say about them) please email us at [email protected]

Toby Ord

Toby Ord

Toby Ord is a Senior Research Fellow at the University of Oxford's Future of Humanity Institute, where his work is focused on existential risk. He founded Giving What We Can, an international society whose members pledge to donate at least 10% of their income to effective charities, and is a key figure in the effective altruism movement, which promotes using reason and evidence to help the lives of others as much as possible.

Toby Ord

Toby Ord

Toby Ord is a Senior Research Fellow at the University of Oxford's Future of Humanity Institute, where his work is focused on existential risk. He founded Giving What We Can, an international society whose members pledge to donate at least 10% of their income to effective charities, and is a key figure in the effective altruism movement, which promotes using reason and evidence to help the lives of others as much as possible.