It is the duty of the human understanding to understand that there are things which it cannot understand, and what those things are. Human understanding has vulgarly occupied itself with nothing but understanding, but if it would only take the trouble to understand itself at the same time it would simply have to posit the paradox.
And, most important, we have to shift our understanding of ourselves as separate individuals, each seeking our own welfare, to an understanding of how we fit into social, biological, and physical environments.
The thing is plain. All that men really understand, is confined to a very small compass; to their daily affairs and experience; to what they have an opportunity to know, and motives to study or practice. The rest is affectation and imposture.
A blind man knows he cannot see, and is glad to be led, though it be by a dog; but he that is blind in his understanding, which is the worst blindness of all, believes he sees as the best, and scorns a guide.