"The only way to avoid error is to have no ideas at all."

"I have been thinking about the nature of things, and I have come to the conclusion that there is a good deal of it."

"It is an unscientific habit to give names to things before we know what they are."

"The human mind is in a state of perpetual oscillation between the actual and the possible."

"Thoroughly conscious ignorance is the prelude to every real advance in science."