You Are Not So Smart – Episode 323 Summary
Guest: Steven Pinker
Topic: Common Knowledge
Date: September 29, 2025

Brief Overview

In this episode, host David McRaney interviews renowned cognitive psychologist Steven Pinker on the concept of "common knowledge," the subject of Pinker’s latest book, When Everyone Knows that Everyone Knows: Common Knowledge and the Mysteries of Money, Power, and Everyday Life. The discussion explores how shared, recursive awareness shapes coordination, language, social norms, institutions, and even political resistance. Pinker provides accessible explanations and thought-provoking examples, from driving conventions to how language evolves—and why authoritarian regimes are obsessed with suppressing public awareness.

Key Discussion Points & Insights

What Is Common Knowledge?

• Defining the Term ([15:09-17:19], [18:06-21:51])

  • Common knowledge is "the state in which I know something, you know it, you know that I know it, I know that you know it, you know that I know that you know it, and so on, ad infinitum." (Steven Pinker, 15:09)
  • Humans don’t literally process infinite recursions; public, conspicuous, or self-evident events stand in for this infinite nesting, allowing us to behave as though we’ve checked those cognitive boxes.
  • "When something is conspicuous, when it is self evident, when it is public, when it is out there, that grants us common knowledge." (Pinker, 15:09)
  • This shared recursive awareness is necessary for coordination—from simple meetings to massive social undertakings.

• Contrast with Similar Terms ([04:48-06:29])

  • Private knowledge: What only one person knows.
  • Shared knowledge: Where some, but not all, are “in the know.”
  • Common knowledge: When “just about everyone” knows, and knows that everyone knows (and so on), enabling societal-level alignment.

The Power of Common Knowledge in Daily Life

• Coordination & Social Conventions ([06:29-09:30], [18:06-21:51])
  • Drives, rituals, norms (traffic laws, weddings, money) function because they’re coordinated on the back of common knowledge.
  • “There is no reason to drive on the right, except there’s a very good reason to drive on the same side that everyone drives on, whichever side that happens to be.” (Pinker, 02:05, reinforced at 21:16)
  • Language works similarly—words maintain meaning through a shared, recursive expectation across speakers.

How Language Evolves: From Common Knowledge to Contention

• Changing Meanings ([21:51-27:54])

  • Dictionaries and usage are followers of how language actually operates; there’s “no authority for what a word means other than the way people use it.” (Pinker, 24:39)
  • Prescriptive advice (e.g., “hopefully,” “nauseous,” “assets”) can lag behind living language, which shifts organically through evolving common knowledge in subcultures or professions.
  • Pinker gives the example of "assets" acquiring a new meaning in media/publisher circles.

• Prototype Theory and the Fuzziness of Definitions ([28:00-34:52])

  • Not all categories have sharp boundaries; we often use prototypes—e.g. the “birdiest bird”—rather than strict definitions.
  • For coordination (in law, medicine), fuzzy everyday categories sometimes must be crisped up through public conventions ("pieces of paper," ceremonies).

The Fallacy of Reification and the Social Reality of Concepts

• Debate with Stephen Jay Gould ([34:52-41:02])

  • Pinker strongly disagrees with Gould's claim that “general intelligence” (g) is a fallacious abstraction.
  • “There has to be some explanation as to why [different types of intelligence] intercorrelate. It is not a fallacy of reification to ask why they intercorrelate.” (Pinker, 37:41)
  • Abstract concepts like "the economy," "money," or "laws" exist as social realities—held up by common knowledge, not physical substance, making them no less real.

• Response to Yuval Noah Harari ([41:02-43:49])

  • Disagrees with Harari’s framing of social realities as “fictions”; prefers to see them as conventions propped up by common knowledge. “It doesn’t literally mean they’re fictions... they exist as common knowledge.”

The Social Dynamics of Relationships, Face, and Politeness

• Common Knowledge and Transitions ([44:50-49:54])
  • Social roles—friendships, loves, authorities—depend on recursive, mutual awareness.
  • Transitions (becoming lovers, changing status) require careful navigation, often through indirect language, tact, politeness, innuendo, and euphemism.
  • Example: Politeness (“Could you pass the salt?”) softens authority implications and preserves the relationship by allowing an “out.”

Authoritarianism, Information, and Coordination

• Suppressing Common Knowledge ([49:54-52:40])

  • Authoritarian regimes fear not dissent in itself, but public, coordinated dissent. They act to prevent common knowledge of opposition (by censoring, banning assembly, etc).
  • "Despotic regimes don't actually care about dissent. They care about common knowledge of dissent." (Pinker, 50:24)
  • Democracies enshrine freedom of assembly and speech precisely to allow coordination and challenge to power.

• Pluralistic Ignorance ([52:40-53:59])

  • When everyone believes others hold a belief (e.g., hazing is cool), but nobody actually does.
  • Enforced by both mutual misunderstanding and sometimes by punishment.
  • Online, this phenomenon can be aggravated by bots and separated information ecosystems.

Notable Quotes and Memorable Moments

• “When something is conspicuous, when it is self evident, when it is public, when it is out there, that grants us common knowledge.”
  — Steven Pinker (15:09)

• “Despotic regimes don't actually care about dissent. They care about common knowledge of dissent... If all the population is disgruntled, but none can act on it in cahoots at the same time, they can control everyone.”
  — Steven Pinker (50:24)

• “There is no authority for what a word means other than the way people use it. The lunatics are running the asylum.”
  — Steven Pinker (24:39)

• “All of our conventions, that is, arbitrary ways of doing things that work, if everyone does them the same way, depend on common knowledge, which can be conveyed tacitly.”
  — Steven Pinker (21:20)

• “Authoritarian regimes are terrified of public protests. Conversely, democracies enshrine freedom of assembly as a fundamental right. All of these are mechanisms of regimes preventing common knowledge.”
  — Steven Pinker (51:30)

• “I argue that that's why we have tact, politeness, innuendo, euphemism, hints, genteel hypocrisy, all cases in which we don't want to explode a relationship that's in force, but we have to do something that contradicts them.”
  — Steven Pinker (46:22)

Timestamps for Important Segments

• [02:05] – Pinker on driving conventions and the essence of coordination
• [14:33-17:19] – Introduction and technical definition of common knowledge
• [18:06-21:51] – How common knowledge works in real life and examples (marriage, language, etc.)
• [21:51-27:54] – Language change, prescriptive vs. descriptive grammar, and evolving common knowledge
• [28:00-34:52] – Prototype categories and the need for conventions in law/science
• [34:52-41:02] – The “reification” of concepts, debate with Gould, and the social reality of abstractions
• [44:50-49:54] – Politeness, face, social rituals, and indirect language as tools for managing common knowledge
• [49:54-52:40] – Common knowledge in authoritarian and democratic regimes
• [52:40-53:59] – Pluralistic ignorance and modern information ecosystems
• [54:09] – Pinker’s hopes for the book’s impact and intended audience

Tone and Style

The episode is intellectually curious, witty, and friendly. McRaney’s enthusiasm for linguistics and Pinker’s clarity make complex ideas accessible and often amusing. Their exchanges are lively, including some nerdy tangents, but always return to real-world implications.

Who Should Listen (or Read the Book)?

As Pinker puts it: “Anyone who's just interested in what makes us tick in social life and the various puzzles, mysteries, fads, crashes, bubbles, rituals, hypocrisies, just human social life on scales from couples to societies.”
— [54:09]

This episode is a must for anyone fascinated by psychology, linguistics, group dynamics, power, politics, or simply the mechanics of why society works (or doesn’t). Pinker’s new book, according to this discussion, is packed with vivid examples, humor, and sharp insights into both mundane and high-stakes aspects of human life.