“Uncertainty is the refuge of hope.”

“It is not what he has, nor even what he does, which directly expresses the worth of a man, but what he is.”

“all appears to change when we change”

“Conquering any difficulty always gives one a secret joy, for it means pushing back a boundary line and adding to one's liberty.”

“Philosophy means the complete liberty of the mind.”

“I begin to realize that my memory is a great catacomb, and that below my actual standing-ground there is layer after layer of historical ashes. Is the life of mind something like that of great tree...”

“The world outside is a strange, but relentless mirror.”

“...an optimistic mind-set finds dozens of possible solutions for every problem that the pessimist regards as incurable.”

“...when dogma enters the brain, all intellectual activity ceases. ”