“Every sentence I utter must be understood not as an affirmation but as a question.[A caution he gives his students, to b...”

“In a republican nation, whose citizens are to be led by reason and persuasion and not by force, the art of reasoning bec...”

“Reason respects the differences and imagination the similitudes of things.”

“We shall require a substantially new manner of thinking if mankind is to survive.”

“Most people would die sooner than think in fact they do.”

“Merely having an open mind is nothing. The object of opening the mind as of opening the mouth is to shut it again on s...”

“To question what I see, then to question what I see after that, because the questions matter as much, perhaps more than,...”

“The test of real and vigorous thinking, the thinking which ascertains truths instead of dreaming dreams, is successful a...”

“Skeptical scrutiny is the means, in both science and religion, by which deep thoughts can be winnowed from deep nonsense...”

“I was too busy fighting the river to worry about adjusting my beliefs in accordance to reality.”

“Those who will not reason, are bigots, those who cannot, are fools, and those who dare not, are slaves.”

“To think is to ignore the differences, to generalize, to abstract.”