The Power of Common Knowledge: Steven Pinker on Language, Norms, and Punishment

Understanding Common Knowledge

• 💡 Common knowledge is a state where everyone knows something, and everyone knows that everyone else knows it, extending infinitely.
• 🧠 This differs significantly from universal private knowledge, where individuals know something but are unaware that others also know it.
• 🧩 Steven Pinker's work, including his new book "When Everyone Knows That Everyone Knows," explores how this concept impacts human interaction, building on his previous research into language and cognition.

Indirect Communication and Deniability

• 💬 Humans often use indirect speech, such as euphemisms, innuendo, or veiled threats and bribes, instead of direct communication.
• 🎭 This indirectness allows for plausible deniability, preventing the creation of common knowledge about an intent or proposition.
• 📌 Avoiding common knowledge through indirectness can help preserve existing relationships by not explicitly challenging underlying fictions or social agreements.

Coordination and Social Norms

• 🤝 Common knowledge is essential for coordination, enabling groups to make arbitrary but complementary choices, like driving on a specific side of the road or using a particular currency.
• ⚖️ Social norms are enforced through public punishment, which creates common knowledge of the norm's violation and subsequent reinforcement, as seen in phenomena like cancel culture.
• 🌍 On the global stage, norms like the nuclear taboo and territorial integrity are crucial for stability, relying on common knowledge to prevent conflict.

Economic and Social Applications

• 💰 The value of fiat money and the success of products like the Macintosh are driven by common knowledge and network effects, where value increases as more people adopt them.
• 🎯 Shelling points (focal points) are conspicuous, arbitrary solutions that help parties coordinate when direct communication or agreement is difficult, such as meeting at a landmark or splitting a negotiation difference.
• 📈 Humor and body language (like blushing or crying) can act as common knowledge generators, signaling shared understanding or subtly challenging social hierarchies.

Honesty, Relationships, and Taboos

• ⚠️ Radical honesty can destabilize relationships because many social bonds rely on shared "fictions" or unspoken understandings that would be challenged if made common knowledge.
• 🗣️ The act of "coming out" (e.g., as gay or even "fat") transforms private knowledge into common knowledge, fundamentally altering social dynamics and relationships.
• 🔬 Debates over researching sensitive topics, such as racial differences in IQ, highlight the tension between scientific inquiry and the potential for common knowledge to be misused as Bayesian priors against individuals.