“Zealous conviction is a dangerous substitute for an open mind.”

“A point of view can be a dangerous luxury when substituted for insight and understanding.”

“Convictions are more dangerous foes of truth than lies.”

“But then with me the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey's mind, if there are any convictions in such a mind?[To William Graham 3 July 1881]”

“A plate of apples, an open fire, and a jolly good book are a fair substitute for heaven.”

“Ah, snug lie those that slumber beneath conviction's roof.Their floors are sturdy lumber, their windows weatherproof.But I sleep cold forever, and cold sleep all my kind,For I was born to shiver in the draft from an open mind.Born nakedly to shiver in the draft of an open mind.”