This is a special post for quick takes by MikkW. Only they can create top-level comments. Comments here also appear on the Quick Takes page and All Posts page.
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.
If you know someone is rational, honest, and well-read, then you probably don't know them all that well. If someone considers you to be rational and honest, and well-read, that indicates they are not.