# Aumann's agreement theorem

### From Lesswrongwiki

**Aumann's agreement theorem**, roughly speaking, says that two agents acting rationally (in a certain precise sense) and with common knowledge of each other's beliefs cannot agree to disagree. More specifically, if two people are genuine Bayesians, share common priors, and have common knowledge of each other's current probability assignments, then they must have equal probability assignments.

## Blog posts

- The Modesty Argument
- Agreeing to Agree by Hal Finney
- The Coin Guessing Game by Hal Finney
- The Proper Use of Humility
- Meme Lineages and Expert Consensus by Carl Shulman (OB)
- Probability Space & Aumann Agreement by Wei Dai
- Bayesian Judo

## External Links

- A write-up of the proof of Aumann's agreement theorem (pdf) by Tyrrell McAllister

## See also

## References

- Robert J. Aumann (1976). "Agreeing to Disagree".
*The Annals of Statistics***4**(6): 1236-1239. ISSN 00905364. (PDF) - Tyler Cowen and Robin Hanson (2004).
*Are Disagreements Honest?*. (PDF, Talk video)

## Tags

- All Less Wrong posts tagged "aumann", "majoritarianism", "disagreement", "modesty"
- Overcoming Bias posts on "Disagreement"