The crucial point is whether you have information about the relative quality of the judgments. If you have information about the absolute quality of your own judgment, that will imply information about the relative quality of the other person’s judgment, given your priors. In theory you can then weight things accordingly.

Neither: treat each judgment as equally likely to be right.

I didn’t say you had no information about the quality of your own judgment.

Further, the tendency of human beings to rely on the judgments of others means that they’re not independent any longer. Ten people agreeing on something as a group does not have the same weight as ten people agreeing on something as individuals.

Neither: treat each judgment as equally likely to be right.

Actually, I am suggesting this, in some cases. If Caledonian sees a small purple unicorn that no one but he can perceive, I would suggest he ponder seriously whether the consensus view (that small purple unicorns do not exist) is correct, and he is hallucinating.

More generally, we should always keep in mind the large error factor in our own perceptual capacities (and even more starkly, the systematic defects in the reliability of our memories). Read some of the literature on the reliability of eyewitness identification testimony, and you will see what I mean. Unless you have reason to believe that you are a more reliable witness than other people, you should follow Robin’s dictum even regarding experiential beliefs.

Except I’m still not convinced the assumption is coherent, let alone true. Maybe I need a rocking chair? I know I’m the one who first used the phrase here (to paraphrase your position, in the antecedent of a conditional), but I would contend that “objectively trivial” is a contradiction in terms.

“Maybe there are some biases we shouldn’t try to overcome for the sake of rationality.”

Probably there are benefits to believing false things, for those who to whom it really doesn’t matter whether their beliefs are true or not, but I’m not in a position to care.

I don’t think my above posts are irrelevant to Robin’s original post. Assuming that the differences in humans’ beliefs are objectively trivial compared to the similarities, the remaining differences might be a diminishing reflection of rationality. Having one eye is unusual because most people have two, but it certainly isn’t irrational to have only one. However, voluntarily popping an eye out is extremely irrational. People don’t do this, we all agree that not popping our eyes out is a good idea, and this is a good reflection of our rationality.

The ways that people most commonly separate themselves are arguably not a matter of rationality in most circumstances. Lets say it is irrational to believe in God. Lots of people do it, and it forces them to exist in a world where basic scientific concepts are denied while other more complex scientific concepts are accepted and made use of every day. To deny evolution but accept cancer treatment… obviously irrational.

But maybe not. What if believing in God allows you to be part of a community that provides you with something that makes your life more comfortable. If you need social support or monetary support, religious affiliation can provide it. Is it irrational to sacrifice a rational belief to obtain something beneficial? If an immigrant who just moved to this country was faced with a choice of believing in evolution or sacrificing that belief to get some help learning English, setting up a small business, and meeting new friends in the community, I would argue that it is irrational to maintain the rational belief in evolution.

I can’t think of any examples where popping out your eyeball is a good idea.

It’s not obvious to me either that there is a well-defined, objective way to compare similarities and differences amongst people without reference to anything else. I simply propose sitting in a comfortable chair, preferably one that rocks, and thinking about it. I would argue that if the differences in humans’ beliefs are objectively trivial compared to the similarities, then the usefulness in exploring these differences to gain insight into human rationality is trivial as well. I would also argue that rationality is not absolute and should be considered relative to the living situations of the people making decisions. If I believe that 1+2=4, and that belief clearly benefits me, then maybe it’s not so irrational to believe. Maybe there are some biases we shouldn’t try to overcome for the sake of rationality.

Use an ignorance prior?

The symmetric corrollary of this is:

“If you have no reason to believe that they have evidence that is worse than yours, you have no reason to accept your own conclusions above theirs, all else being equal.”

So if you have no information at all about the quality of the observers’ judgment, how should you respond? By disregarding your own judgment and accepting theirs, or retaining yours and ignoring theirs?