The remaining souls are all eagerly straining to keep up, but are unable to rise; they are carried around below the surface, trampling and striking one another as each tries to get ahead of the others.  The result is terribly noisy, very sweaty, and disorderly.  Many souls are crippled by the incompetence of their drivers, and many wings break much of their plumage.  After so much trouble, they all leave without having seen reality, uninitiated, and when they have gone they will depend on what they think is nourishment—their own opinions.

Socrates, speaking in Plato’s Phaedrus