The idea that, although oneself is full of mysterious and impenetrable depths, other people are quite easy to understand, is part of the belief in one's own superiority which most people carry about with them in spite of its statistical improbability. Like all contemptuous opinions, it makes the world seem less interesting than it really is.
Source: "On labelling people" [From: Mortals and Others: Bertrand Russell's American Essays, 1931-1935, v.1 (1975)]
More info.: https://russell-j.com/LABEL.HTM"