Homo Deus - Summary, Notes and Highlights

Homo Deus - Summary, Notes and Highlights

by | 15 min read

Homo Deus is a thought-provoking book that attempts to look into what the future might hold for humanity given the direction that current technologies are taking us.

These are my notes and highlights from the book Homo Deus by Yuval Noah Harari.

🤔 What Is This Book About?

Leading on from Yuval’s previous book Sapiens, Homo Deus is a thought-provoking book that attempts to look into what the future might hold for humanity given the direction that current technologies are taking us.

👤 Who Should Read It?

This book is for anyone with an interest in technology and who wants a glimpse into what the future might hold for humanity as the capabilities of technology go beyond human abilities.

📒 Summary & Notes

This book is broken down into 3 main parts:

  1. Homo Sapiens Conquer the World
  2. Homo Sapiens Gives Meaning to the World
  3. Homo Sapiens Loses Control

New Human Agenda

For thousands of years, 3 main problems have occupied humanity: Famine, Plague and War.

Civilisations used to pray to the gods to make the harvest better, presume it was the devil that sent disease and went to war with each other over whose beliefs were right and which God was the correct one to worship.

In today’s world, these 3 problems are mostly a thing of the past, they are manageable problems.

We still have famine in areas of the world but this is not due to a lack of food but a government failure. We no longer put the cause down to “God’s will” but because someone must have screwed up.

Indeed, in most countries today overeating has become a far worse problem than famine. In the eighteenth century Marie Antoinette allegedly advised the starving masses that if they ran out of bread, they should just eat cake instead. Today, the poor are following this advice to the letter. Whereas the rich residents of Beverly Hills eat lettuce salad and steamed tofu with quinoa, in the slums and ghettos the poor gorge on Twinkie cakes, Cheetos, hamburgers and pizza.

We now have a much better understanding of illness and diseases and with the help of vaccines, we have managed to wipe out some plagues completely.

War still happens but at a much smaller scale than it ever did before. Countries are more likely to come to another arrangement before things escalate to war.

So with Famine, Plague and War mostly solved, what problems is humanity trying to solve for now?

Yuval Noah Harari suggests that humanity’s next targets are Immortality, Happiness and Divinity.


Medicine has managed to progress enough that we now know how to treat the majority of diseases. At some point, technology may advance enough that we will even be able to solve other illnesses such as cancer by using nano-bots that travel through our bodies fixing problems.

Given all our advances in medicine, you would have thought that the maximum age of people would have increased. Yes, the average life spans of people have increased as more people are escaping famine, plague and war. However, the average age for those that did escape those 3 has always had a natural life span of 70 - 80 years old.

For example, Galileo Galilei died at 77, Isaac Newton at 84 and Michelangelo at 88. Even chimpanzees in the jungle sometimes live into their sixties.

Companies such as Google (Google’s Calico) are trying to solve death and bring about immortality.


Until now most of our efforts have been around increasing the productivity of workers so that we can increase the GDP of the country and increase the amount of money that the government has.

So instead of trying to optimise for happiness instead we have been optimising for what will make the nation stronger and the most money for the economy.

Free health care wasn’t for people’s health but to keep them working longer.

The aim wasn’t to make people happy, but to make the nation stronger. The country needed sturdy soldiers and workers, healthy women who would give birth to more soldiers and workers, and bureaucrats who came to the office punctually at 8 a.m. instead of lying sick at home.

In recent years people are taking happiness and mental health more seriously.


Once we have conquered immortality and happiness what is left?

Technology has accelerated at an alarming pace over the last 100 years. Every year new upgrades our coming out for our phones, laptops and televisions. However, despite being surrounded by technological abundance the human body has hardly changed from our hunter-gatherer days.

We are becoming more and more dependent on technology every day. If you misplace your smartphone it often feels like you have lost a limb.

Whether it be smart watches or diabetic sensors we are already starting to use technologies to enhance our bodies.

In the future, we may be able to upgrade our bodies in the same way we do our smartphones. Whether that be sharpened senses, improved strength or a better memory. Merging our organic bodies with non-organic devices.

Cyborg engineering will go a step further, merging the organic body with non-organic devices such as bionic hands, artificial eyes, or millions of nano-robots that will navigate our bloodstream, diagnose problems and repair damage.

As we know with all of our devices, technology comes at a cost and not everyone will be able to afford to enhance themselves with technology. This may well bring about a divide between humans and the superhuman.

Paradox of Knowledge

The more we learn the more we try and change the world for the better. However, now we have so much knowledge that we can’t keep up with it all.

In the past human knowledge increased slowly and as a result politics and economics can change with it. Now our knowledge increases at such a breakneck speed that we are constantly changing at an ever faster pace. Who knows what the world will look like in 2050? What we can be sure of is it will likely look very different today.

This is the paradox of historical knowledge. Knowledge that does not change behaviour is useless. But knowledge that changes behaviour quickly loses its relevance. The more data we have and the better we understand history, the faster history alters its course, and the faster our knowledge becomes outdated

Part I: Homo Sapiens Conquer the World

The first part of this book tries to answer how Homo Sapiens have come to conquer the world. What special abilities do Homo Sapiens poses that other mammals do not?

We have already become god-like with respect to the other animals we share this planet with. However, does that mean that the other animals are below us?

We have treated animals as a means to an end to our survival. Domesticated animals now make up more of the earth’s biomass than humans and wild animals put together.

We are still driven by our genetic urges:

Why do modern humans love sweets so much? Not because in the early twenty-first century, we must gorge on ice cream and chocolate in order to survive. Rather, it is because when our Stone Age ancestors came across sweet fruit or honey, the most sensible thing to do was to eat as much of it as quickly as possible

Through the use of the written word and imagined constructs, we have managed to construct mass cooperation networks.

Our chimpanzee cousins cannot invent and spread such stories, which is why they cannot cooperate in large numbers.

Sapiens rule the world because only they can weave an intersubjective web of meaning: a web of laws, forces, entities and places that exist purely in their common imagination. This web allows humans alone to organise crusades, socialist revolutions and human rights movements.

Other animals may also imagine various things. A cat waiting to ambush a mouse might not see the mouse, but may well imagine the shape and even taste of the mouse. Yet to the best of our knowledge, cats are able to imagine only things that actually exist in the world, like mice. They cannot imagine things that they have never seen or smelled or tasted – such as the US dollar, Google corporation or the European Union. Only Sapiens can imagine such chimeras.

Part II: Homo Sapiens Gives Meaning to the World

For centuries God has provided meaning to humanity. No matter what suffering you have endured in your life religion promises everlasting happiness in the afterlife.

The written word has become law and now affects our decisions more than it should:

Our modern education systems provide numerous other examples of reality kowtowing to written records. When measuring the width of my desk, the yardstick I am using matters little. The width of my desk remains the same whether I say it is 200 centimetres or 78.74 inches. However, when bureaucracies measure people, the yardsticks they choose make all the difference. When schools began assessing people according to precise numerical marks, the lives of millions of students and teachers changed dramatically.

School used to be for teaching and enlightening children. Now they are more focused on teaching students to get high marks.

The key question, though, is whether this is the right yardstick for measuring success. A school principal would say: ‘Our system works. During the last five years, exam results have risen by 7.3 per cent.’ Yet is that the best way to judge a school?

Where has all this cooperation and progress got us? People now work longer hours and are not as happy as our hunter-gather ancestors.

After centuries of economic growth and scientific progress, life should have become calm and peaceful, at least in the most advanced countries. If our ancestors knew what tools and resources stand ready at our command, they would have surmised that we must be enjoying celestial tranquillity, free of all cares and worries. The truth is very different. Despite all our achievements, we feel a constant pressure to do and produce even more.

Suppose you were given a choice between the following two vacation packages:

Stone Age package:

On day one we will hike for ten hours in a pristine forest, setting camp for the night in a clearing by a river. On day two we will canoe down the river for ten hours, camping on the shores of a small lake. On day three we will learn from the native people how to fish in the lake and how to find mushrooms in the nearby woods.

Modern proletarian package:

On day one we will work for ten hours in a polluted textile factory, passing the night in a cramped apartment block. On day two we will work for ten hours as cashiers in the local department store, going back to sleep in the same apartment block. On day three we will learn from the native people how to open a bank account and fill out mortgage forms.

Which package would you choose?


  • Religion - deals with ethics
  • Science - deals with facts

A lot of the conflicts between religion and science have been around what religion believes are facts. God created the universe.

Now humanity has found meaning in the human experience in the wonders of human intelligence and creativity.

War exposes the truth about life, and awakens the will for power, for glory and for conquest. Nietzsche summed it up by saying that war is ‘the school of life’ and that ’what does not kill me makes me stronger’.

It is not just Kelly Clarkson who said that then.

The book describes a letter from Lieutenant Henry Jones of the British Army to his brother. In it, he describes how war has shown him how petty everyday life is and that he is glad that he got to go to war.

You have, in fact, realised an ideal, which, as far as I can see, you very rarely do in ordinary life. The reason is that ordinary life runs on a commercial and selfish basis

One of the things that got Hitler voted in was his experience in the trenches. He learnt something about life that others could relate to.

When Hitler appealed to the German voters and asked for their trust, he could muster only one argument in his favour: his experiences in the trenches had taught him what you can never learn at university, at general headquarters or at a government ministry. People followed him and voted for him because they identified with him, and because they too believed that the world is a jungle and that what doesn’t kill us only makes us stronger.

Part III: Homo Sapiens Loses Control

Our decisions are based on electrical signals in our brains. Do we really control them or do they control us?

If by ‘free will’ you mean the ability to act according to your desires – then yes, humans have free will, and so do chimpanzees, dogs and parrots. When Polly wants a cracker, Polly eats a cracker. But the million-dollar question is not whether parrots and humans can act out their inner desires – the question is whether they can choose their desires in the first place.

Our left and right sides of the brains contradict each other:

Furthermore, the experiencing self is often strong enough to sabotage the best-laid plans of the narrating self. I might, for instance, make a New Year’s resolution to start a diet and go to the gym every day. Such grand decisions are the monopoly of the narrating self. But the following week when it’s gym time, the experiencing self takes over. I don’t feel like going to the gym, and instead, I order pizza, sit on the sofa and turn on the TV.

This reminds me of experiments done on people who had brain damage such that the left-hand side of the brain didn’t talk to the right-hand side.

The experiments showed that one side of the brain will put reasoning behind the actions caused by the other side of the brain.

See: Roger Sperry’s Split Brain Experiments (1959–1968)

What happens if we managed to silence the inner noise in our heads:

I calmly line up my rifle, take a moment to breathe deeply, and pick off the closest one, before tranquilly assessing my next target. In what seems like next to no time, I hear a voice call out, “Okay, that’s it.” The lights come up in the simulation room In the sudden quiet amid the bodies around me, I was really expecting more assailants, and I’m a bit disappointed when the team begins to remove my electrodes. I look up and wonder if someone wound the clocks forward. Inexplicably, twenty minutes have just passed. “How many did I get?” I ask the assistant. She looks at me quizzically. “All of them.”

The experiment changed Sally’s life. In the following days, she realised she had been through a “near-spiritual experience” …

What defined the experience was not feeling smarter or learning faster: the thing that made the earth drop out from under my feet was that for the first time in my life, everything in my head finally shut up. My brain without self-doubt was a revelation. There was suddenly this incredible silence in my head. I hope you can sympathise with me when I tell you that the thing I wanted most acutely for the weeks following my experience was to go back and strap on those electrodes. I also started to have a lot of questions.

Who was I apart from the angry bitter gnomes that populate my mind and drive me to failure because I’m too scared to try? And where did those voices come from?

Our brains come up with reasons for our suffering:

Business corporations often sink millions into failed enterprises, while private individuals cling to dysfunctional marriages and dead-end jobs. Our narrating self would much prefer to continue suffering in the future, just so it won’t have to admit that our past suffering was devoid of all meaning. Eventually, if we want to come clean about past mistakes, our narrating self must invent some twist in the plot that will infuse these mistakes with meaning.

Robots have replaced many manual labour jobs. In the future, with the rise of artificial intelligence, they may even replace more complicated jobs like doctors.

A host of tough technical problems still prevent Watson and its ilk from replacing most doctors tomorrow morning. Yet these technical problems – however difficult – need only be solved once. The training of a human doctor is a complicated and expensive process that lasts years. When the process is complete, after ten years of studies and internships, all you get is one doctor. If you want two doctors, you have to repeat the entire process from scratch. In contrast, if and when you solve the technical problems hampering Watson, you will get not one, but an infinite number of doctors, available 24/7 in every corner of the world. So even if it costs $100 billion to make it work, in the long run, it would be much cheaper than training human doctors.

This is becoming more true with the recent advancements we have seen in AI such as ChatGPT.

Since we do not know what the job market will look like in 2030 or 2040, already today we have no idea what to teach our kids.

Most of what they currently learn at school will probably be irrelevant by the time they are forty. Traditionally, life has been divided into two main parts: a period of learning followed by a period of working. Very soon this traditional model will become utterly obsolete, and the only way for humans to stay in the game will be to keep learning throughout their lives and to reinvent themselves repeatedly. Many if not most humans may be unable to do so.

What will everyone do with their lives when they can’t work?

There is definitely going to be a need for universal income in the future as so many people are going to find themselves shut out of the job market quite quickly as AI takes over more jobs.

The most important question in twenty-first-century economics may well be what to do with all the superfluous people. What will conscious humans do, once we have highly intelligent non-conscious algorithms that can do almost everything better?

In the twenty-first century our personal data is probably the most valuable resource most humans still have to offer, and we are giving it to the tech giants in exchange for email services and funny cat videos.

This is the main issue with centralised social networks. They have too much power with what they know about us. I am looking forward to decentralised networks becoming more prevalent in the future.

When everybody uses the same oracle, and everybody believes the oracle, the oracle turns into a sovereign.

However, most relevant research has been conducted on people from Western, educated, industrialised, rich and democratic (WEIRD) societies, who do not constitute a representative sample of humanity. The study of the human mind has so far assumed that Homo sapiens is Homer Simpson.


People who follow the data religion believe that we can no longer cope with the immense flow of information and that we should put our trust in big data and computer algorithms.

Humans were supposed to distil data into information, information into knowledge, and knowledge into wisdom. However, Dataists believe that humans can no longer cope with the immense flows of data, hence they cannot distil data into information, let alone into knowledge or wisdom.

Dataists are sceptical about human knowledge and wisdom and prefer to put their trust in Big Data and computer algorithms.

Algorithms could decide everything from who we should date, what to eat, what we should do for a living and when to go to the AI doctor.

Computers will have so much data on us that they will understand us better than ourselves.

Yet once authority shifts from humans to algorithms, the humanist projects may become irrelevant. Once we abandon the homo-centric worldview in favour of a data-centric worldview, human health and happiness may seem far less important. Why bother so much about obsolete data-processing machines when much better models are already in existence?

Dataism thereby collapses the barrier between animals and machines and expects electronic algorithms to eventually decipher and outperform biochemical algorithms.

When cars replaced horse-drawn carriages, we didn’t upgrade the horses - we retired them. Perhaps it is time to do the same with Homo sapiens.

If we think in terms of decades, then global warming, growing inequality and the disruption of the job market loom large. Yet if we take the really grand view of life, all other problems and developments are overshadowed by three interlinked processes:

  1. Science is converging on an all-encompassing dogma, which says that organisms are algorithms and life is data processing.
  2. Intelligence is decoupling from consciousness.
  3. Non-conscious but highly intelligent algorithms may soon know us better than we know ourselves.

These three processes raise three key questions, which I hope will stick in your mind long after you have finished this book:

  1. Are organisms really just algorithms, and is life really just data processing?
  2. What’s more valuable - intelligence or consciousness?
  3. What will happen to society, politics and daily life when non-conscious but highly intelligent algorithms know us better than we know ourselves?

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