It’s comforting to think those who disagree with our beliefs are simply irrational. But that isn’t the case. Many complex factors motivate beliefs, and properly understanding them is vital.

I'm surprised people aren't talking more about evidence based probabilistic rational choice/decision modeling (like Bayes). There's a paper exploring whether prejudice can be modeled rationally at

Unsurprisingly the answer is no, prejudice is definitively irrational. Obviously that's a more restricted context (prejudice) but rationality modeling seems a good way of explaining why/when saying someone is irrational is justified. Probability based reasoning is probably more useful than the reliance on simple logical form that some in this thread want to rely on.

So anyway: saying "everyone has their reasons" covered a multitude of rational sins, and it is the case that some people (within certain beliefs or contexts) can be accurately described as irrational.

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