
Big Ideas Harvard firebrand on intellectual freedom Steven Pinker with Natasha Mitchell
Feb 18, 2026
Steven Pinker, Harvard psychologist and bestselling author, discusses common knowledge, cancel culture and how public beliefs drive coordination. He talks about progress measured by data, tribalism and media fractionation, the psychology of punishment over argument, and how common knowledge shapes hoarding, markets, protest and authoritarian power.
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Common Knowledge Enables Coordination
- Common knowledge requires infinite mutual awareness (I know that you know that I know...).
- Steven Pinker explains it enables coordination on conventions like driving sides and currency acceptance.
Expectations Drive Economic Panics
- Recursive mentalizing drives market bubbles and bank runs through expectations about others' expectations.
- Pinker links Keynes's speculation idea to common-knowledge dynamics in finance.
How A Joke Sparked A Shortage
- Johnny Carson joked about a toilet-paper shortage during the 1970s oil embargo and people began hoarding it.
- Pinker uses this to show how a conspicuous public remark became common belief and caused a real shortage.











