What Happens When We All Know? | Brian Greene & Steven Pinker

How do humans understand each other, cooperate, and build civilizations? Brian Greene sits down with Harvard cognitive scientist Steven Pinker — author of the newly released When Everyone Knows That Everybody Knows — for a deep dive into the psychology of common knowledge, the evolution of language, and the invisible rules that make society possible.

They explore why we laugh, cry, and signal emotions, how shared understanding and social norms hold civilization together, and what happens when those norms break down. The conversation also tackles AI vs human intelligence, misinformation, and whether shared truth can survive in a fragmented digital world.

This program is part of the Rethinking Reality series, supported by the John Templeton Foundation.

Participant: Steven Pinker
Moderator: Brian Greene

0:00:00 Introduction: Steven Pinker on Language, Mind, and Human Nature
0:00:44 The Monty Hall Puzzle and the Power of Common Knowledge
0:07:39 How Shared Understanding Helped Humans Thrive
0:21:08 The Origins of Language: Daniel Dor’s “Instructing the Imagination”
0:25:17 Pinker vs. Chomsky: Where Language and Thought Diverge
0:29:39 Common Knowledge and the Hidden Logic of Social Norms
0:34:18 When Norms Break: The Psychology Behind Modern Politics
0:40:32 The Architecture of Communication: How We Exchange Ideas
0:42:43 The Metaphor That Drives Civilization
0:48:25 Institutions, Bias, and the Fragility of Collective Truth
0:53:06 Artificial Intelligence and the Evolution of Understanding
0:58:34 Consciousness, Language, and the Limits of Machines
1:01:03 Can We Ever Test for Consciousness?
1:02:43 What AI Reveals About the Human Mind
1:06:03 Credits

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