Common Knowledge

A game theory concept describing information that everyone knows AND everyone knows that everyone knows (and so on, recursively). Common knowledge is more powerful than private knowledge because it enables coordinated action. Everyone may privately know the emperor has no clothes, but until someone says it publicly—making it common knowledge—no one acts on it. Announcements, public commitments, and visible signals create common knowledge that enables groups to coordinate in ways that private, distributed knowledge cannot.

When to use it

When an 'open secret' isn't changing behavior (it's not yet common knowledge); when you need to coordinate action across a group; when public commitments or announcements are more effective than private ones; when understanding why making private knowledge public can be transformative.

How it can help

When you need to change group behavior, make the relevant information common knowledge—not just known, but known to be known. This is why public announcements change behavior when private conversations don't. 'Everyone knows our culture is toxic' is private knowledge that produces no change; a CEO publicly naming the problem makes it common knowledge that demands response. In strategy: creating common knowledge (public commitments, announced deadlines, visible metrics) enables coordination that private information cannot.