Naked Truths: The Logic of Who Knows What
In his new book, Steven Pinker shows how the seemingly simple idea of shared knowledge can explain much of social life.
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In Hans Christian Andersen’s famous story, everyone could see that the emperor has no clothes. But only a kid had the boldness, if due to ignorance, to blurt it out. This created the common knowledge that he was naked, which allowed for the revolt to begin.
Steven Pinker’s new book “When everyone knows that everyone knows…” analyzes this kind of phenomena. The Canadian cognitive psychologist formalizes the logic of common knowledge: “With private knowledge, person A knows something, and person B knows it. With common knowledge, A knows something, and B knows it, but in addition A knows that B knows it, and B knows that A knows it, and so on, ad infinitum.” What looks like a simple story about a child’s honesty becomes the key to understanding how the perception of common perception turns into coordination.
«What looks like a simple story about a child’s honesty becomes the key to understanding how the perception of common perception turns into coordination.»
The degree to which information moves from private to shared to common knowledge changes how people act at every stage. Pinker shows how private dissatisfaction can become common with an old Soviet joke about a man handing out blank leaflets in Moscow. When arrested and interrogated, he tells the police: “What is there to write? It’s so obvious.” As Pinker explains, dictators fear speech not only because it changes minds, but also because it reveals that minds have already changed. Private discontent becomes dangerous only when it becomes public knowledge, for example in a public protest. “Each protester can not only see the others but see that the others are seeing the others.”
What Pinker does not stress enough is that the external cue which creates common knowledge can also arise from within. Because people differ in every conceivable dimension (boldness, ignorance, intelligence…), a single person, whether the child who speaks the truth about the emperor or the dissident who lifts a blank page, can become the cue that others were waiting for. The signal is still external, but it is generated from within; the shape of the distribution itself becomes the source of common knowledge. Both the kid and the dissident rightly thought others might not be in the same spot. This made a public announcement worthwhile. Variance creates arbitrage opportunities.
«The signal is still external, but it is generated from within; the shape of the distribution itself becomes the source of common knowledge.»
When it comes to relationships, we constantly navigate what should and should not be made public, which truths should remain politely unspoken. These “benign hypocrisies” allow coexistence by preventing every perception from becoming shared knowledge “You would be ill-advised to tell your boss that you have mused about killing him, or to inform either your spouse or a colleague that you daydream about sleeping with the latter… The announcement would pollute the pool of assumptions that allow you to get along.” This happens because by not voicing our thoughts, we demonstrate a kind of buffer, proof to others that we can restrain impulses everyone is assumed to have. The person most likely to attack others is the one shouting and disparaging them. It’s analogous to owning a gun but keeping it holstered: when people follow the social rule of not drawing their weapons, or not telling colleagues about their sexual desires, fewer violent incidents and cases of harassment occur.
In the digital age, this boundary dissolves, “When it’s common knowledge that someone has breached a norm, people feel it must become common knowledge that they are punished,” Pinker writes. Outrage spreads because visibility has become effortless, and every act of seeing confirms that everyone else has seen. The same mechanism that once brought down empires now sustains social media mobs.
Pinker shows how one simple idea can explain much of social life. The same logic explains why jokes spread, why dictators fear laughter, why markets fall apart, and why apologies restore trust, all through the fragile move from private to shared to common knowledge. The book rewires how we perceive society. After reading it, one begins to see the silent choreography of awareness everywhere, who knows, who knows that others know, and who pretends not to.
Steven Pinker: When Everyone Knows That Everyone Knows… Common Knowledge and the Mysteries of Money, Power, and Everyday Life. New York: Viking, 2025.
