Preface: I exclude those irrational beliefs whose cause was the lack of technology, because there is nothing more to discuss if technology suffices to explain these irrational beliefs.

I ask this question because I wish to comprehend more deeply how and why intelligent people believe(d) irrational or stupid things. The most immediate example of an irrational belief is racism by the most eminent philosophers.

Evidently, some of these people must not have been 'stupid'.

Then the next insulting modifiers are probably: 'biased', 'ignorant', 'prejudiced'. But somehow, these Emotive Words or Question-Begging Epithets do not suffice to explain their irrationality.

Please also suggest books, if this question concerns a branch of philosophy on its own.

  • Because people are not, nor will ever be, perfectly rational. I guarantee you that both you and I hold -- firmly hold -- beliefs, right now, in our heads, which future generations would find laughable or damnable or both. The problem is we, in the current moment, can't know which (though I strongly suspect within a century young people will be asking me "did you really eat animals?!"). That's why the standard advice is to not judge historical persons by modern standards. Norms and mores change. We must judge people by the standards of their time.
    – Dan Bron
    Commented Jun 8, 2016 at 13:30

3 Answers 3


You can reach an irrational conclusion because of following reasons -

  1. Ignorance - That is not knowing enough to make a conclusion

  2. Bias - Stressing on some things(properties) that are not as dominant as they appear

  3. Mistake - Deriving a conclusion wrongly from a premise

  4. Justification by current knowledge/belief - Justifying something to be a result of something that is already believed or known to be true

Example - For a simple syllogism -

  1. If A then B

  2. A

  3. B

You can make a mistake in first premise or second. Either that can be because you do not know exceptions (ignorance) or you end up believing something to be true/dominant when it is not (bias). Other than that, you can make an honest mistake or make a wrong conclusion by justifying what you know or think to be true from current knowledge/belief.

It is mostly a combination of these factors. Consider that in earlier times people believed in miasma theory. You can call it ignorance but it was partly true. There had to be a reason why people who were otherwise healthy would fell to diseases. As air could be felt but germs could neither be felt nor seen, the culprit was decided. It was a result of both ignorance and justification by current knowledge/belief.


check your premises about who is intelligent.

anyway, the underlying issue is people disagree about stuff. there are lots of ideas out there. many of them conflict. sorting it out is hard. being intelligent and reasonable in no way prevents someone from making a mistake when judging some ideas that disagree. it's hard.

a secondary issue is that people have bad methods of judging ideas. they're bad at discussing hard issues to conclusions. they don't really know how and they kinda wing it and mistakes are common. if anyone would like to improve at this, a good place to start is this book https://www.amazon.com/Understanding-Objectivism-Guide-Learning-Philosophy-ebook/dp/B006LU1P6G/ or this discussion forum https://groups.yahoo.com/neo/groups/fallible-ideas/info


Yes, it is quite frightening that there are still in 2016 plenty of people on the wrong side of history. For instance, there are still people who have faith in their little concepts of irrationality, rationality, modalities, realism, anti-realism, intersubjectivty, universality, truth(-value, gotcha haha!), especially outside formal languages. There are even people who have faith in their contrived formal languages and other abstractions to what they call ''reach reality''.

  • This doesn't appear to answer the question. It appears to merely repeat that the phenomenon (or some version of it) exists.
    – virmaior
    Commented Jun 9, 2016 at 8:05

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