Cognitive psychologist and best-selling author Steven Pinker explains how thinking about how other people think shapes our relationships, economies, politics, and culture.

Thinking about what other people know about the things that we know might tie us up in knots, but it's something we all do on a daily basis without even realizing.

This is known as 'common knowledge' — to cross the street safely, pay for our groceries, or meet someone for a drink, we have to be sure we all have a shared understanding of crosswalks, currency, time, and many other things.

Steven Pinker is a Professor of Psychology at Harvard University and the author of many bestselling books on language, cognition, and social relations.

In his 2025 book, When Everyone Knows That Everyone Knows..., Pinker explores how common knowledge, language, expectations, and conventions shape our society and daily lives.