Don't need to posit crazy things, just think about selection bias -- are the sorts of people that tend to become rationalist randomly sampled from the population? If not, why wouldn't there be blind spots in such people just based on that?
Yes, but if I get the idea right, it is to learn to think in a self-correcting, self-improving way. For example, maybe Kanazawa is right in intelligence suppressing instincts / common sense, but a consistent application of rationality sooner or later would lead to discovering it and forming strategies to correct it.
For this reason, it is more of the rules (of self-correction, self-improvement, self-updating sets of beliefs) than the people. What kinds of truths would be potentially invisible to a self-correcting observationalist ruleset even if this was practiced by all kinds of people?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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