“A man who is certain he is right is almost sure to be wrong.”

“There’s nothing quite as frightening as someone who knows they are right.”

“It is right that we should stand by and act on our principles; but not right to hold them in obstinate blindness, or retain them when proved to be erroneous.”

“Shall we educate ourselves in what is known, and then casting away all we have acquired, turn to ignorance for aid to guide us among the unknown?”

“In place of practising wholesome self-abnegation, we ever make the wish the father to the thought: we receive as friendly that which agrees with, we resist with dislike that which opposes us; whereas the very reverse is required by every dictate of common sense.”

“Nothing is too wonderful to be true if it be consistent with the laws of nature.”

“No matter what you look at, if you look at it closely enough, you are involved in the entire universe.”