How Common Knowledge Shapes the World | Steven Pinker | TED

Overview

Steven Pinker delves into the concept of common knowledge and its profound influence on human coordination, relationships, and societal norms. Through vivid examples and humor, he explores how shared understanding shapes everything from protests to financial markets, and why its breakdown can threaten harmony.

Notable Quotes

- 100,000 Englishmen cannot control 350 million Indians if the Indians refuse to cooperate. – Gandhi, as referenced by Pinker, on the power of collective action.

- If I seem unduly clear to you, you must have misunderstood what I said. – Alan Greenspan, on the strategic ambiguity of central bankers.

- What's there to say? It's so obvious. – Anonymous Soviet-era joke, highlighting the subversive power of common knowledge.

🧠 The Logic of Common Knowledge

- Pinker explains the distinction between private knowledge (what individuals know) and common knowledge (what everyone knows that everyone knows).

- Common knowledge is essential for coordination, as illustrated by Hans Christian Andersen’s The Emperor’s New Clothes, where the boy’s statement transforms private realizations into collective awareness.

- Thomas Schelling’s example of a separated couple in Manhattan demonstrates how common knowledge simplifies decision-making in coordination dilemmas.

📣 Power of Public Events and Protests

- Public demonstrations create common knowledge among participants, enabling collective action.

- Pinker references Gandhi’s insight that collective non-cooperation can dismantle oppressive systems, as seen in India’s independence movement.

- He recounts a Soviet-era joke about blank protest signs to illustrate how even silence or ambiguity can generate subversive common knowledge.

💸 Financial Markets and Speculative Bubbles

- Pinker likens speculative investing to a beauty contest where success depends on predicting others’ choices, creating cycles of recursive thinking.

- He critiques cryptocurrency ads that rely on creating common expectations rather than intrinsic value, warning of the fragility of bubbles.

- Financial crises, such as bank runs, occur when doubt becomes common knowledge, triggering mass panic.

👀 Social Relationships and Innuendo

- Relationships rely on common knowledge, reinforced through signals like eye contact, blushing, and laughter.

- Pinker explains how innuendo and euphemism allow people to veil intentions, avoiding the creation of explicit common knowledge that could disrupt relationships.

- Examples include the evolution of veiled propositions, from “etchings” to “Netflix and chill,” and the strategic ambiguity of bribes and threats.

🌍 Norms and Global Stability

- Social and international norms, such as driving conventions or the taboo against nuclear weapons, are upheld by common acceptance.

- Pinker warns that these norms are fragile and can collapse if overtly flouted or undermined by loose talk.

- He underscores the stakes of maintaining these norms, noting their role in preserving peace and civility.