“But to live in ignorance on such a point was impossible.”

“I wouldn't have seen the light if she hadn't pointed out, but once sje did, it became impossible to ignore.”

“It is not enough that you understand in what ignorance man and beast live; you must also have and acquire the will to ignorance. You need to grasp that without this kind of ignorance life itself would be impossible, that it is a condition under which alone the living thing can preserve itself and prosper: a great, firm dome of ignorance must encompass you.”

“It is impossible to defeat an ignorant man in argument.”

“If youth were not ignorant and timid, civilization would be impossible.”

“Ignorance is of a peculiar nature; once dispelled, it is impossible to reestablish it. It is not originally a thing of itself, but is only the absence of knowledge; and though man may be kept ignorant, he cannot be made ignorant.”