The Tree of Knowledge

The physical world stayed exactly as physical as it had always been, but social reality suddenly became negotiable in a way it never had been before.

Language, in this account, became something far more powerful than a set of warning cries about predators nearby. It began carrying gossip, tracking reputation, and managing the subtle, shifting politics of a small group — who could be trusted, who had cheated whom, who was sleeping with whom. Anthropologist Robin Dunbar's research on primate group size is one of the threads Harari weaves in here: gossip-capable language let human groups stay socially coherent at sizes well beyond what grooming-based bonding among other primates could support.

Even more strangely, and far more consequentially, human language also began carrying stories about things that don't physically exist at all and that no one could ever touch: guardian spirits, clan identities, abstract rules of conduct, and imagined debts owed between people who had never met. No chimpanzee troop, however socially sophisticated, has ever organized around a myth.

Once a large group of people can genuinely believe in the same invented order, Harari's central claim is that it can cooperate at a scale far beyond anything kinship alone makes possible. Hundreds of people, then thousands, then eventually millions, can act as if they are one coordinated body, purely because they trust the same shared story — a nation, a religion, a currency. This is the hinge on which the rest of human history turns: a real lion fears only teeth and claws, but a human being will fear laws, gods, and flags that have no physical existence whatsoever, and will willingly die defending them.

Harari's favourite modern illustration is the car company Peugeot. The company is not its factories, its workers, or its cars — all of those could vanish and Peugeot would still exist, because it is a legal fiction, a limited liability company that lives in the shared belief of lawyers, shareholders, and courts. That is the Cognitive Revolution's trick in miniature: a story that many strangers believe becomes a powerful actor in the world.