Homo Deus: A Brief History of Tomorrow

by Yuval Noah Harari

Dedication To my teacher, S. N. Goenka (1924–2013), who lovingly taught me important things.

For the first time in history, more people die today from eating too much than from eating too little; more people die from old age than from infectious diseases; and more people commit suicide than are killed by soldiers, terrorists and criminals combined.

In 2012 about 56 million people died throughout the world; 620,000 of them died due to human violence (war killed 120,000 people, and crime killed another 500,000). In contrast, 800,000 committed suicide, and 1.5 million died of diabetes.23 Sugar is now more dangerous than gunpowder.

Whereas in 2010 obesity and related illnesses killed about 3 million people, terrorists killed a total of 7,697 people across the globe, most of them in developing countries.25 For the average American or European, Coca-Cola poses a far deadlier threat than al-Qaeda.

In most cases, this overreaction to terrorism poses a far greater threat to our security than the terrorists themselves.

In ancient Greece the philosopher Epicurus explained that worshipping gods is a waste of time, that there is no existence after death, and that happiness is the sole purpose of life. Most people in ancient times rejected Epicureanism, but today it has become the default view. Scepticism about the afterlife drives humankind to seek not only immortality, but also earthly happiness. For who would like to live for ever in eternal misery?

Jeremy Bentham declared that the supreme good is ‘the greatest happiness of the greatest number’, and concluded that the sole worthy aim of the state, the market and the scientific community is to increase global happiness.

In 1776 the Founding Fathers of the United States established the right to the pursuit of happiness as one of three unalienable human rights, alongside the right to life and the right to liberty.

The glass ceiling of happiness is held in place by two stout pillars, one psychological, the other biological. On the psychological level, happiness depends on expectations rather than objective conditions. We don’t become satisfied by leading a peaceful and prosperous existence. Rather, we become satisfied when reality matches our expectations. The bad news is that as conditions improve, expectations balloon. Dramatic improvements in conditions, as humankind has experienced in recent decades, translate into greater expectations rather than greater contentment. If we don’t do something about this, our future achievements too might leave us as dissatisfied as ever.

On the biological level, both our expectations and our happiness are determined by our biochemistry, rather than by our economic, social or political situation. According to Epicurus, we are happy when we feel pleasant sensations and are free from unpleasant ones. Jeremy Bentham similarly maintained that nature gave dominion over man to two masters – pleasure and pain – and they alone determine everything we do, say and think. Bentham’s successor, John Stuart Mill, explained that happiness is nothing but pleasure and freedom from pain, and that beyond pleasure and pain there is no good and no evil. Anyone who tries to deduce good and evil from something else (such as the word of God, or the national interest) is fooling you, and perhaps fooling himself too.35

According to the life sciences, happiness and suffering are nothing but different balances of bodily sensations. We never react to events in the outside world, but only to sensations in our own bodies. Nobody suffers because she lost her job, because she got divorced or because the government went to war. The only thing that makes people miserable is unpleasant sensations in their own bodies. Losing one’s job can certainly trigger depression, but depression itself is a kind of unpleasant bodily sensation. A thousand things may make us angry, but anger is never an abstraction. It is always felt as a sensation of heat and tension in the body, which is what makes anger so infuriating. Not for nothing do we say that we ‘burn’ with anger. Conversely, science says that nobody is ever made happy by getting a promotion, winning the lottery or even finding true love. People are made happy by one thing and one thing only – pleasant sensations in their bodies.

This is all the fault of evolution. For countless generations our biochemical system adapted to increasing our chances of survival and reproduction, not our happiness.

Perhaps the key to happiness is neither the race nor the gold medal, but rather combining the right doses of excitement and tranquillity; but most of us tend to jump all the way from stress to boredom and back, remaining as discontented with one as with the other.

To attain real happiness, humans need to slow down the pursuit of pleasant sensations, not accelerate it.

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.

To understand all this we need to go back and investigate who Homo sapiens really is, how humanism became the dominant world religion and why attempting to fulfil the humanist dream is likely to cause its disintegration. This is the basic plan of the book.

But the Anthropocene isn’t a novel phenomenon of the last few centuries. Already tens of thousands of years ago, when our Stone Age ancestors spread from East Africa to the four corners of the earth, they changed the flora and fauna of every continent and island on which they settled. They drove to extinction all the other human species of the world, 90 per cent of the large animals of Australia, 75 per cent of the large mammals of America and about 50 per cent of all the large land mammals of the planet – and all before they planted the first wheat field, shaped the first metal tool, wrote the first text or struck the first coin.6

The authors of the book of Genesis may have preserved a remnant of archaic animist beliefs in Eve’s name, but they took great care to conceal all other traces. Genesis says that, instead of descending from snakes, humans were divinely created from inanimate matter. The snake is not our progenitor: he seduces us to rebel against our heavenly Father. While animists saw humans as just another kind of animal, the Bible argues that humans are a unique creation, and any attempt to acknowledge the animal within us denies God’s power and authority. Indeed, when modern humans discovered that they actually evolved from reptiles, they rebelled against God and stopped listening to Him – or even believing in His existence.

Unfortunately, humans can cause tremendous suffering to farm animals in various ways, even while ensuring their survival and reproduction. The root of the problem is that domesticated animals have inherited from their wild ancestors many physical, emotional and social needs that are redundant on human farms. Farmers routinely ignore these needs, without paying any economic penalty. They lock animals in tiny cages, mutilate their horns and tails, separate mothers from offspring and selectively breed monstrosities. The animals suffer greatly, yet they live on and multiply.

The human farmers take care of everything the sow needs in order to survive and reproduce. She is given enough food, vaccinated against diseases, protected against the elements and artificially inseminated. From an objective perspective, the sow no longer needs to explore her surroundings, socialise with other pigs, bond with her piglets or even walk. But from a subjective perspective, the sow still feels very strong urges to do all of these things, and if these urges are not fulfilled she suffers greatly. Sows locked in gestation crates typically display acute frustration alternating with extreme despair.15

In fact, attributing emotions to pigs doesn’t humanise them. It ‘mammalises’ them. For emotions are not a uniquely human quality – they are common to all mammals (as well as to all birds and probably to some reptiles and even fish). All mammals evolved emotional abilities and needs, and from the fact that pigs are mammals we can safely deduce that they have emotions.16

It took scientists many years to acknowledge this. Not long ago psychologists doubted the importance of the emotional bond between parents and children even among humans. In the first half of the twentieth century, and despite the influence of Freudian theories, the dominant behaviourist school argued that relations between parents and children were shaped by material feedback; that children needed mainly food, shelter and medical care; and that children bonded with their parents simply because the latter provide these material needs. Children who demanded warmth, hugs and kisses were thought to be ‘spoiled’. Childcare experts warned that children who were hugged and kissed by their parents would grow up to be needy, egotistical and insecure adults.

Only in the 1950s and 1960s did a growing consensus of experts abandon these strict behaviourist theories and acknowledge the central importance of emotional needs. In a series of famous (and shockingly cruel) experiments, the psychologist Harry Harlow separated infant monkeys from their mothers shortly after birth, and isolated them in small cages. When given a choice between a metal dummy-mother fitted with a milk bottle, and a soft cloth-covered dummy with no milk, the baby monkeys clung to the barren cloth mother for all they were worth. Those baby monkeys knew something that John Watson and the experts of Infant Care failed to realise: mammals can’t live on food alone. They need emotional bonds too. Millions of years of evolution preprogrammed the monkeys with an overwhelming desire for emotional bonding. Evolution also imprinted them with the assumption that emotional bonds are more likely to be formed with soft furry things than with hard and metallic objects. (This is also why small human children are far more likely to become attached to dolls, blankets and smelly rags than to cutlery, stones or wooden blocks.) The need for emotional bonds is so strong that Harlow’s baby monkeys abandoned the nourishing metal dummy and turned their attention to the only object that seemed capable of answering that need. Alas, the cloth-mother never responded to their affection and the little monkeys consequently suffered from severe psychological and social problems, and grew up t...

In recent years, as people began to rethink human–animal relations, such practices have come under increasing criticism. We are suddenly showing unprecedented interest in the fate of so-called lower life forms, perhaps because we are about to become one. If and when computer programs attain superhuman intelligence and unprecedented power, should we begin valuing these programs more than we value humans? Would it be okay, for example, for an artificial intelligence to exploit humans and even kill them to further its own needs and desires? If it should never be allowed to do that, despite its superior intelligence and power, why is it ethical for humans to exploit and kill pigs? Do humans have some magical spark, in addition to higher intelligence and greater power, which distinguishes them from pigs, chickens, chimpanzees and computer programs alike? If yes, where did that spark come from, and why are we certain that an AI could never acquire it? If there is no such spark, would there be any reason to continue assigning special value to human life even after computers surpass humans in intelligence and power? Indeed, what exactly is it about humans that make us so intelligent and powerful in the first place, and how likely is it that non-human entities will ever rival and surpass us?

Darwin has deprived us of our souls. If you really understand the theory of evolution, you understand that there is no soul.

Philosophers have encapsulated this riddle in a trick question: what happens in the mind that doesn’t happen in the brain? If nothing happens in the mind except what happens in our massive network of neurons – then why do we need the mind?

Take, for example, the Ultimatum Game – one of the most famous experiments in behavioural economics. This experiment is usually conducted on two people. One of them gets $100, which he must divide between himself and the other participant in any way he wants. He may keep everything, split the money in half or give most of it away. The other player can do one of two things: accept the suggested division, or reject it outright. If he rejects the division, nobody gets anything. Classical economic theories maintain that humans are rational calculating machines. They propose that most people will keep $99, and offer $1 to the other participant. They further propose that the other participant will accept the offer. A rational person offered a dollar will always say yes. What does he care if the other player gets $99? Classical economists have probably never left their laboratories and lecture halls to venture into the real world. Most people playing the Ultimatum Game reject very low offers because they are ‘unfair’. They prefer losing a dollar to looking like suckers. Since this is how the real world functions, few people make very low offers in the first place. Most people divide the money equally, or give themselves only a moderate advantage, offering $30 or $40 to the other player. The Ultimatum Game made a significant contribution to undermining classical economic theories and to establishing the most important economic discovery of the last few decades: Sapiens don’t behav...

In another recent experiment, the primatologist Frans de Waal placed two capuchin monkeys in two adjacent cages, so that each could see everything the other was doing. De Waal and his colleagues placed small stones inside each cage, and trained the monkeys to give them these stones. Whenever a monkey handed over a stone, he received food in exchange. At first the reward was a piece of cucumber. Both monkeys were very pleased with that, and happily ate their cucumber. After a few rounds de Waal moved to the next stage of the experiment. This time, when the first monkey surrendered a stone, he got a grape. Grapes are much more tasty than cucumbers. However, when the second monkey gave a stone, he still received a piece of cucumber. The second monkey, who was previously very happy with his cucumber, became incensed. He took the cucumber, looked at it in disbelief for a moment, and then threw it at the scientists in anger and began jumping and screeching loudly. He ain’t a sucker.23

In 1740 King Frederick II of Prussia invaded Silesia, thus commencing a series of bloody wars that earned him his sobriquet Frederick the Great, turned Prussia into a major power and left hundreds of thousands of people dead, crippled or destitute. Most of Frederick’s soldiers were hapless recruits, subject to iron discipline and draconian drill. Not surprisingly, the soldiers lost little love on their supreme commander. As Frederick watched his troops assemble for the invasion, he told one of his generals that what struck him most about the scene was that ‘we are standing here in perfect safety, looking at 60,000 men – they are all our enemies, and there is not one of them who is not better armed and stronger than we are, and yet they all tremble in our presence, while we have no reason whatsoever to be afraid of them’.24 Frederick could indeed watch them in perfect safety. During the following years, despite all the hardships of war, these 60,000 armed men never revolted against him – indeed, many of them served him with exceptional courage, risking and even sacrificing their very lives.

People find it difficult to understand the idea of ‘imagined orders’ because they assume that there are only two types of realities: objective realities and subjective realities. In objective reality, things exist independently of our beliefs and feelings. Gravity, for example, is an objective reality. It existed long before Newton, and it affects people who don’t believe in it just as much as it affects those who do. Subjective reality, in contrast, depends on my personal beliefs and feelings. Thus, suppose I feel a sharp pain in my head and go to the doctor. The doctor checks me thoroughly, but finds nothing wrong. So she sends me for a blood test, urine test, DNA test, X-ray, electrocardiogram, fMRI scan and a plethora of other procedures. When the results come in she announces that I am perfectly healthy, and I can go home. Yet I still feel a sharp pain in my head. Even though every objective test has found nothing wrong with me, and even though nobody except me feels the pain, for me the pain is 100 per cent real. Most people presume that reality is either objective or subjective, and that there is no third option. Hence once they satisfy themselves that something isn’t just their own subjective feeling, they jump to the conclusion it must be objective. If lots of people believe in God; if money makes the world go round; and if nationalism starts wars and builds empires – then these things aren’t just a subjective belief of mine. God, money and nations must therefore ...

As well as separating humans from other animals, this ability to create intersubjective entities also separates the humanities from the life sciences. Historians seek to understand the development of intersubjective entities like gods and nations, whereas biologists hardly recognise the existence of such things. Some believe that if we could only crack the genetic code and map every neuron in the brain, we will know all of humanity’s secrets. After all, if humans have no soul, and if thoughts, emotions and sensations are just biochemical algorithms, why can’t biology account for all the vagaries of human societies? From this perspective, the crusades were territorial disputes shaped by evolutionary pressures, and English knights going to fight Saladin in the Holy Land were not that different from wolves trying to appropriate the territory of a neighbouring pack. The humanities, in contrast, emphasise the crucial importance of intersubjective entities, which cannot be reduced to hormones and neurons. To think historically means to ascribe real power to the contents of our imaginary stories. Of course, historians don’t ignore objective factors such as climate changes and genetic mutations, but they give much greater importance to the stories people invent and believe. North Korea and South Korea are so different from one another not because people in Pyongyang have different genes to people in Seoul, or because the north is colder and more mountainous. It’s because the north...

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?

Fiction isn’t bad. It is vital. Without commonly accepted stories about things like money, states or corporations, no complex human society can function. We can’t play football unless everyone believes in the same made-up rules, and we can’t enjoy the benefits of markets and courts without similar make-believe stories. But the stories are just tools. They should not become our goals or our yardsticks. When we forget that they are mere fiction, we lose touch with reality. Then we begin entire wars ‘to make a lot of money for the corporation’ or ‘to protect the national interest’. Corporations, money and nations exist only in our imagination. We invented them to serve us; how come we find ourselves sacrificing our lives in their service?

Religion is a deal, whereas spirituality is a journey. Religion gives a complete description of the world, and offers us a well-defined contract with predetermined goals. ‘God exists. He told us to behave in certain ways. If you obey God, you’ll be admitted to heaven. If you disobey Him, you’ll burn in hell.’ The very clarity of this deal allows society to define common norms and values that regulate human behaviour. Spiritual journeys are nothing like that. They usually take people in mysterious ways towards unknown destinations. The quest usually begins with some big question, such as who am I? What is the meaning of life? What is good? Whereas many people just accept the ready-made answers provided by the powers that be, spiritual seekers are not so easily satisfied. They are determined to follow the big question wherever it leads, and not just to places you know well or wish to visit. Thus for most people, academic studies are a deal rather than a spiritual journey, because they take us to a predetermined goal approved by our elders, governments and banks. ‘I’ll study for three years, pass the exams, get my BA certificate and secure a well-paid job.’ Academic studies might be transformed into a spiritual journey if the big questions you encounter on the way deflect you towards unexpected destinations, of which you could hardly even conceive at first. For example, a student might begin to study economics in order to secure a job in Wall Street. However, if what she lear...

The entire contract can be summarised in a single phrase: humans agree to give up meaning in exchange for power.

Bashing free-market capitalism is high on the intellectual agenda nowadays. Since capitalism dominates our world, we should indeed make every effort to understand its shortcomings, before they cause apocalyptic catastrophes. Yet criticising capitalism should not blind us to its advantages and attainments. So far, it’s been an amazing success – at least if you ignore the potential for future ecological meltdown, and if you measure success by the yardstick of production and growth. In 2016 we may be living in a stressful and chaotic world, but the doomsday prophecies of collapse and violence have not materialised, whereas the scandalous promises of perpetual growth and global cooperation are fulfilled. Although we experience occasional economic crises and international wars, in the long run capitalism has not only managed to prevail, but also to overcome famine, plague and war.

However, humanism offered an alternative. As humans gained confidence in themselves, a new formula for attaining ethical knowledge appeared: Knowledge = Experiences × Sensitivity. If we wish to know the answer to any ethical question, we need to connect to our inner experiences, and observe them with the utmost sensitivity. In practice, that means that we seek knowledge by spending years collecting experiences, and sharpening our sensitivity so we could understand these experiences correctly. What exactly are ‘experiences’? They are not empirical data. An experience is not made of atoms, molecules, proteins or numbers. Rather, an experience is a subjective phenomenon that includes three main ingredients: sensations, emotions and thoughts. At any particular moment my experience comprises everything I sense (heat, pleasure, tension, etc.), every emotion I feel (love, fear, anger, etc.) and whatever thoughts arise in my mind. And what is ‘sensitivity’? It means two things. Firstly, paying attention to my sensations, emotions and thoughts. Secondly, allowing these sensations, emotions and thoughts to influence me. Granted, I shouldn’t allow every passing breeze to sweep me away. Yet I should be open to new experiences, and permit them to change my views, my behaviour and even my personality. Experiences and sensitivity build up one another in a never-ending cycle. I cannot experience anything if I have no sensitivity, and I cannot develop sensitivity unless I undergo a variety...

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.

The decision to press either the right or left switch certainly reflected the person’s choice. Yet it wasn’t a free choice. In fact, our belief in free will results from faulty logic. When a biochemical chain reaction makes me desire to press the right switch, I feel that I really want to press the right switch. And this is true. I really want to press it. Yet people erroneously jump to the conclusion that if I want to press it, I choose to want to. This is of course false. I don’t choose my desires. I only feel them, and act accordingly.

In reality, there is only a stream of consciousness, and desires arise and pass within this stream, but there is no permanent self who owns the desires, hence it is meaningless to ask whether I choose my desires deterministically, randomly or freely. It may sound extremely complicated, but it is surprisingly easy to test this idea. Next time a thought pops up in your mind, stop and ask yourself: ‘Why did I think this particular thought? Did I decide a minute ago to think this thought, and only then did I think it? Or did it just arise in my mind, without my permission or instruction? If I am indeed the master of my thoughts and decisions, can I decide not to think about anything at all for the next sixty seconds?’ Just try, and see what happens.

Nevertheless, most people identify with their narrating self. When they say ‘I’, they mean the story in their head, not the stream of experiences they undergo. We identify with the inner system that takes the crazy chaos of life and spins out of it seemingly logical and consistent yarns. It doesn’t matter that the plot is full of lies and lacunas, and that it is rewritten again and again, so that today’s story flatly contradicts yesterday’s; the important thing is that we always retain the feeling that we have a single unchanging identity from birth to death (and perhaps even beyond the grave). This gives rise to the questionable liberal belief that I am an individual, and that I possess a consistent and clear inner voice, which provides meaning for the entire universe.

Western, educated, industrialised, rich and democratic (WEIRD) societies,

The humanist revolution caused modern Western culture to lose faith and interest in superior mental states, and to sanctify the mundane experiences of the average Joe. Modern Western culture is therefore unique in lacking a special class of people who seek to experience extraordinary mental states. It believes anyone attempting to do so is a drug addict, mental patient or charlatan. Consequently, though we have a detailed map of the mental landscape of Harvard psychology students, we know far less about the mental landscapes of Native American shamans, Buddhist monks or Sufi mystics.

As the Austrian economics guru Friedrich Hayek explained, ‘In a system in which the knowledge of the relevant facts is dispersed among many people, prices can act to coordinate the separate actions of different people.’

Data-processing considerations also explain why capitalists favour lower taxes. Heavy taxation means that a large part of all available capital accumulates in one place – the state coffers – and consequently more and more decisions have to be made by a single processor, namely the government. This creates an overly centralised data-processing system. In extreme cases, when taxes are exceedingly high, almost all capital ends up in the government’s hands, and so the government alone calls the shots. It dictates the price of bread, the location of bakeries, and the research-and-development budget. In a free market, if one processor makes a wrong decision, others will be quick to utilise its mistake. However, when a single processor makes almost all the decisions, mistakes can be catastrophic.

Yet mixing godlike technology with myopic politics also has its downside. Lack of vision isn’t always a blessing, and not all visions are necessarily bad. In the twentieth century, the dystopian Nazi vision did not fall apart spontaneously. It was defeated by the equally grand visions of socialism and liberalism. It is dangerous to trust our future to market forces, because these forces do what’s good for the market rather than what’s good for humankind or for the world. The hand of the market is blind as well as invisible, and left to its own devices it may fail to do anything about the threat of global warming or the dangerous potential of artificial intelligence.

We often imagine that democracy and the free market won because they were ‘good’. In truth, they won because they improved the global data-processing system.

So over the last 70,000 years humankind first spread out, then separated into distinct groups, and finally merged again. Yet the process of unification did not take us back to the beginning. When the different human groups fused into the global village of today, each brought along its unique legacy of thoughts, tools and behaviours, which it collected and developed along the way. Our modern larders are now stuffed with Middle Eastern wheat, Andean potatoes, New Guinean sugar and Ethiopian coffee. Similarly, our language, religion, music and politics are replete with heirlooms from across the planet.

If humankind is indeed a single data-processing system, what is its output? Dataists would say that its output will be the creation of a new and even more efficient data-processing system, called the Internet-of-All-Things. Once this mission is accomplished, Homo sapiens will vanish.

Twenty years ago Japanese tourists were a universal laughing stock because they always carried cameras and took pictures of everything in sight. Now everyone is doing it. If you go to India and see an elephant, you don’t look at the elephant and ask yourself, ‘What do I feel?’ – you are too busy looking for your smartphone, taking a picture of the elephant, posting it on Facebook and then checking your account every two minutes to see how many Likes you got. Writing a private diary – a common humanist practice in previous generations – sounds to many present-day youngsters utterly pointless. Why write anything if nobody else can read it? The new motto says: ‘If you experience something – record it. If you record something – upload it. If you upload something – share it.’