"The fundamental cause of the trouble is that in the modern world the stupid are
cocksure while the intelligent are full of doubt."
This seems to be the Dunning-Kruger effect in action. Knowing more means having greater awareness that what you know is only a small part of what you could know.https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
"A hundred years ago the philosophical radicals formed a school of intelligent
men who were just as sure of themselves as the Hitlerites are"
If true, I wonder what caused this. Could anyone suggest cultural, social or technological reasons that may have temporarily united the intellectuals of the age?