What’s common about common knowledge, and how does it become common? Common knowledge—the awareness of how others think and even how others think others think—is needed for social coordination, things as basic as driving on the same side of the road or using paper currency. And it has a hidden logic that makes it all work.

Cognitive psychologist and author Steven Pinker returns to Commonwealth Club World Affairs in Silicon Valley to explore some of the paradoxes of human behavior. It’s the subject of his latest book, When Everyone Knows That Everyone Knows . . .: Common Knowledge and the Mysteries of Money, Power, and Everyday Life.

Pinker addresses issues as seemingly disparate as why people hoard toilet paper when an emergency breaks, why crypto ads clog up Super Bowl advertising, why Russian officials arrested a protester carrying a blank sign, or even why everyone seems to agree that life would be unbearable if everyone was completely honest at all times. Tying it all together, he says, is our ability to know what others think and what others think about what others think . . . on and on, ad infinitum.

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