The key to understanding this fairy tale, and much of what we’re going to discuss in this book, is the concept of common knowledge.10 For a piece of information to be “common knowledge” within a group of people, it’s not enough simply for everyone to know it. Everyone must also know that everyone else knows it, and know that they know that they know it, and so on. It could as easily be called “open” or “conspicuous knowledge.”
