Key ideas from Steven Pinker

• Common knowledge requires infinite recursion: 'I know that you know that I know' ad infinitum, distinguishing it from mere shared private knowledge
• When Everyone Knows That Everyone Knows explores how common knowledge enables civilization through currency, government power, and social coordination
• Eye contact, laughter, blushing, and crying function as 'common knowledge generators' - making private experiences publicly visible to all parties
• Veiled communication like 'Netflix and chill' maintains plausible deniability by avoiding explicit common knowledge while preserving relationship dynamics
• Bank runs and toilet paper shortages demonstrate how common knowledge can become 'virulent' - spreading rapidly through society with real consequences
• Political polarization stems from fractured common knowledge pools, where different groups no longer share the same baseline assumptions about reality
• Johnny Carson's Tonight Show joke about toilet paper shortage in the 1970s actually created the shortage by making the concern common knowledge
• Trump's presidency succeeded by flouting norms that 'were inviolable only because people thought they were inviolable' - breaking shared expectations