Steven Pinker on The Recursive Loop That Made Us Human

"In Hans Christian Andersen's folktale, The Emperor's New Clothes, when a child cries out that the emperor is naked, he isn't revealing a secret. Everyone already knows it. What changes in that instant is that everyone now knows that everyone else knows. That shift-from mutual knowledge to common knowledge, from private recognition to public awareness-topples the illusion. It's also the central insight of cognitive scientist Steven Pinker's new book, When Everyone Knows That Everyone Knows...: Common Knowledge and the Science of Harmony, Hypocrisy, and Outrage."

"Pinker argues that this layered awareness-knowing that others know that you know-binds societies together and, at times, tears them apart. From cooperation and civility to hypocrisy and moral outrage, our social lives depend on nested models of what others think. His book reveals the hidden logic behind these loops of awareness-how they govern polite conversation, collective action, and even the stability of nations."

"With ordinary mutual knowledge, each person knows a fact. With common knowledge, everyone knows it, and everyone knows that everyone else knows it-and everyone knows that everyone else knows that, in an infinite regress. Human brains can't compute endless loops, so we rely on public cues and shared signals-eye contact, rituals, news headlines-to establish common knowledge without consciously working through each recursive level. A public protest or viral post changes behavior not by adding information but by making that information publicly self-evident."

Common knowledge arises when everyone knows a fact and also knows that everyone else knows it, creating recursive awareness that can extend indefinitely. Humans cannot compute infinite regressions, so societies use public cues and shared signals—eye contact, rituals, headlines—to establish common knowledge efficiently. Public events such as protests or viral posts alter behavior not by adding information but by making information publicly self-evident. This shared awareness enables coordination, stabilizes markets and institutions, and makes reputations consequential. The same mechanism also enables hypocrisy, fuels moral outrage, and can trigger collective action or collapse when widely acknowledged norms or deceptions become common knowledge.

Read at Psychology Today