From my shortform:
If you know someone is rational, honest, and well-read, then you can learn a good bit from the simple fact that they disagree with you.
If you aren’t sure someone is rational and honest, their disagreement tells you little.
If you know someone considers you to be rational and honest, the fact that they still disagree with you after hearing what you have to say, tells you something.
But if you don’t know that they consider you to be rational and honest, their disagreement tells you nothing.
It’s valuable to strive for common knowledge of you and your partners’ rationality and honesty, to make the most of your disagreements.
This is a restatement of the ideas behind Aumann’s Agreement Theorem. On Less Wrong, one can often assume that a writer or commentor is interested in rationality, but that doesn’t mean that the writer can be assumed to actually be rational.
How can we help build common knowledge of people’s rationality and honesty?
I think we should perhaps start with actual truth, then move to knowledge. No human is perfectly rational nor honest. The VAST majority of humans have some topics on which they’re quite irrational, and some topics (with fair overlap) on which they’re quite dishonest.
The current common doubt is pretty close to the territory.
There’s one idea of how to build common knowledge of honesty from my shortform. I know I got some pushback from it, and I’m too tired right now to address those concerns, but I’ll share what I wrote to help get the conversation going: