This was a very interesting analysis by PhilGoetz how "reason" can be thought of a memetic immune disorder. The idea is that people have lot of belives which might come from religion or tradition or culture. Since belives are often very general, they might not generalize well. In a situtation where live with that belive for a long time with people who's behaviour are based on similar belives you learn socially which parts of belives to follow and which you shouldn't. When some one tries to reason out those belives they loose the immunity they loose the immunity they have gained from the herd and try to apply the rules where where they shouldn't be used. EY puts is pretty well "rationality (is) a failure of compartmentalization - the attempt to take everything you hear seriously."