This is the final exam for Common Knowledge & Coordination. It pulls together the whole course: the ladder from private to mutual to common knowledge, why a public signal changes behaviour when a pile of private ones does not, focal points and coordination games, the real faces of the model — bank runs, revolutions, advertising, and censorship — and the places where the idealisation breaks. Take your time and reason each one through.
How this exam works
Read carefully — this exam is final. Each question appears one at a time. Once you submit an answer it is locked for good: there’s no going back, no retry, and no restart. Your score is hidden until the end, where you’ll see a pass/fail verdict. The pass mark is 70%. A few questions ask you to select all correct answers.
What is the precise difference between mutual knowledge and common knowledge?
Select an answer to continue.
Course Recap
Big picture
Common knowledge & coordination, in one picture
- Common Knowledge
- The ladder
- Private → mutual → everyone knows that everyone knows
- The engine
- Public signals and focal points make it common
- The games
- Stag Hunt, equilibrium selection, critical mass
- Real faces
- Bank runs, revolutions, ads, censorship
- Where it breaks
- Two generals, false common knowledge, approximations
- The ladder
Key takeaways
Coordinated, risky action needs more than everyone privately knowing a fact — it needs common knowledge, where everyone knows that everyone knows, without end. A pile of private signals never gets you there; a single public signal, seen by all at once, does — which is exactly what the child’s shout, a Super Bowl advert, a visible crowd, and a free press all manufacture. That is why coordination games have multiple equilibria (a bad, everyone-plays-safe outcome can be perfectly stable), why bank runs and revolutions are self-fulfilling and surprise everyone, and why regimes attack the common-knowledge channel first. But it is an idealisation: no finite string of confirmations ever truly closes the tower, false common knowledge coordinates a crowd just as well as true, and a focal point or a little critical mass can do the job without everyone knowing everything. Read for what is common, not merely shared — and you will see the hidden signal behind the crowd.