Steven Pinker on How Common Knowledge Builds and Weakens Societies

Understanding Common Knowledge

• 💡 Common knowledge is defined as a state where everyone knows that everyone knows something, and this awareness extends infinitely.
• 🎯 It is generated implicitly when something is conspicuous, public, or self-evident, allowing individuals to perceive shared awareness without explicit communication.
• 🔑 This concept is fundamental for social coordination, enabling groups to make arbitrary but adaptive choices, such as driving on a specific side of the road, because everyone expects others to do the same.

Coordination and Game Theory

• 📌 Shelling points are salient, self-evident focal points that facilitate coordination in the absence of direct communication, like a famous landmark for a rendezvous.
• ✅ The Stag Hunt game illustrates how common knowledge enables cooperation for mutual benefit, as both parties have an interest in achieving the best collective outcome.
• ⚠️ In contrast, the Prisoner's Dilemma demonstrates how individual rational defection can lead to a suboptimal outcome for all, where communication (often termed "cheap talk") is ineffective.

Common Knowledge in Politics

• ⚡ Dictatorships actively suppress common knowledge through censorship and restrictions on assembly to prevent collective action and maintain their power.
• 📈 Public events like elections or protests can become "shelling points" that generate common knowledge, potentially galvanizing opposition to a regime.
• 🧠 The "madman theory" in international relations relies on creating common knowledge that a leader is irrational to gain advantage in a game of chicken, making them unpredictable.

Social Rituals and Communication

• ✨ Rituals and ceremonies (e.g., weddings, inaugurations) publicly establish common knowledge, solidifying social relationships and new equilibria.
• 🎭 Indirect speech, euphemisms, and hints are used to avoid generating common knowledge when directness would be disruptive or undesirable, preserving existing social dynamics.
• ⚖️ Strategic ambiguity (e.g., US policy on Taiwan, Israel's nuclear status) is a rational form of hypocrisy that prevents common knowledge to avoid escalation or maintain delicate balances.

Cultural Context and Polarization

• 🌍 Cultures exhibit systematic differences in directness versus politeness, reflecting varying strategies for managing common knowledge in social interactions.
• 🚨 The fragmentation of media and social networks can lead to competing "common knowledges" within different sub-communities, fueling political polarization.
• 🔍 Pluralistic ignorance occurs when individuals privately disbelieve something but assume everyone else believes it, often due to fear, preventing common knowledge of the true sentiment.