When Everyone Knows That Everyone Knows

As a cognitive scientist, the ultimate subject of Steven Pinker’s fascination is how we think about each other’s thoughts, ad infinitum. It sounds impossible, but Steven Pinker shows that we do it all the time. This awareness, which we experience as something that is public or “out there,” is called common knowledge, and it has a momentous impact on our social, political, and economic lives.

Common knowledge, Pinker shows, can make sense of many of life’s enigmas: financial bubbles and crashes, revoluti