I am currently reading the book "Le nouvel âge de la bêtise" by Pierre André Taguieff. Unfortunately, the author gives a lot of examples of this "new stupidity", but he doesn't give a definition of stupidity.

I like Kant's definition best, which he says is a "lack of judgment" (= Mangel an Urteilskraft), whereby for him judgment is the ability to subsume sensory impressions under the concepts of reason. (Kant: "intellectual concepts as such are empty, mere perceptions are blind) . This ability of judgment is therefore the "hinge" between the world outside and the world of ideas and concepts. If this hinge is defective, as in the case of stupidity, then the ideas and concepts work idly, in a void, so to speak, without any connection to reality.

This is particularly the case with all kinds of ideologies which, as the word suggests, are not about one thing (such as life in biology or the soul in psychology), but are only about ideas and their connections to one another. Ideologies are therefore always a sign of stupidity, as they lack a link to reality. Ideologies arise when ideas only have sex with each other, when they pile up into grandiose intellectual buildings (philosophies, theologies, theories....) that can be very impressive, even internally very coherent, but if they lack a connection to reality, then they are a case of stupidity.

This is also the reason why stupidity is not the opposite of intelligence, because there are very intelligent people who are also very stupid, namely when they only use their intelligence to play with ideas and theories, detached from reality (Nowadays there are whole departments at universities where very intelligent and very stupid people gather and "study". One sign is: They don't call their subjects "science", but "---- Studies".

Well, following Immanuel Kant, this is my idea of stupidity. How would you define it?