Overcoming Bias : Agreeing to Agree

overcomingbiasOvercoming Bias : Agreeing to Agree.
By Hal Finney · December 10, 2006 4:01 pm

It’s been mentioned a few times already, but I want to draw attention to what is IMO probably the most interesting, surprising and challenging result in the field of human bias: that mutually respectful, honest and rational debaters cannot disagree on any factual matter once they know each other’s opinions. They cannot “agree to disagree”, they can only agree to agree.

This result goes back to Nobel Prize winner Robert Aumann in the 1970s: Agreeing to Disagree. Unfortunately Aumann’s proof is quite static and formal, building on a possible-world semantics formalism so powerful that Aumann apologizes: “We publish this note with some diffidence, since once one has the appropriate framework, it is mathematically trivial.” It’s ironic that a result so counter-intuitive and controversial can be described in such terms. This combination of elegance and parsimony of proof combined with the totally unexpected nature of the result is part of what makes this area so fascinating to me.