Steven Pinker on Common Knowledge

EconTalk

Library of Economics and Liberty

Ethics, Philosophy, Economics, Books, Science, Business, Courses, Social Sciences, Society & Culture, Interviews, Education, History

4.7 • 4.3K Ratings

🗓️ 22 September 2025

⏱️ 83 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

Why are Super Bowl ads so good for launching certain kinds of new products? Why do we all drive on the same side of the road? And why, despite laughing and crying together, do we often misread what others think? According to bestselling author and Harvard psychologist Steven Pinker, it all comes down to common knowledge, or the phenomenon that happens when everyone knows that everyone else knows something. Hear Pinker and EconTalk's Russ Roberts explore the necessary conditions for that knowledge, and how it can be both vital and dangerous to societies, depending on how it's used. They discuss, among other things, game-theory puzzles, how laughter spreads, how totalitarian regimes exploit uncertainty about who knows what (even when they don't), and why we often don't say explicitly what we really mean to say.

Transcript

Click on a timestamp to play from that location

0:00.0	Welcome to Econ Talk, Conversations for the Curious, part of the Library of Economics and Liberty.
0:07.9	I'm your host, Russ Roberts, of Sholem College in Jerusalem and Stanford University's Hoover Institution.
0:13.8	Go to EconTalk.org, where you can subscribe, comment on this episode, and find links and other information related to today's conversation.
0:21.2	You'll also find our archives with every episode we've done going back to 2006.
0:26.7	Our email address is mail at econTalk.org.
0:30.0	We'd love to hear from you.
0:36.7	Today is September 2nd, 2025, and my guest is Cognitive Psychologist and author Stephen Pinker,
0:42.9	the Johnstone Family Professor of Psychology at Harvard University.
0:46.7	His latest book and the subject of today's conversation is,
0:50.3	When Everyone Knows That Everyone Knows, Common Knowledge knowledge and the mysteries of money, power,
0:57.1	and everyday life. Stephen, welcome to Econ Talk.
1:00.6	Thank you.
1:01.5	At the heart of the book is this idea of common knowledge, which has an everyday meaning,
1:07.1	but you also mean it in a more technical way. What do you mean by common knowledge?
1:13.0	Common knowledge refers to the state where A knows something, B knows it, A knows that B knows it,
1:20.2	B knows that A knows it, B knows that A knows it at infinitum.
1:25.9	And part of this, there's an attempt at some point in the book to answer the question
1:33.8	of whether this is feasible at the deepest level, at the fullest level.
1:39.3	Talk a little bit about that.
1:41.6	Some of the book is applied game theory, which involves
1:46.8	recursive reasoning in various ways by the participants, sometimes mathematically. That's important.
1:53.1	So give us your take on, quote, how realistic this assumption is of common knowledge and
	...

Please login to see the full transcript.

Previous episode | Next episode

Disclaimer: The podcast and artwork embedded on this page are from Library of Economics and Liberty, and are the property of its owner and not affiliated with or endorsed by Tapesearch.

Generated transcripts are the property of Library of Economics and Liberty and are distributed freely under the Fair Use doctrine. Transcripts generated by Tapesearch are not guaranteed to be accurate.