Karl Popper

"I am a pessimist because of intelligence, but an optimist because of will."

"The beginning of all science is wonder."

"We must distinguish between the context of discovery and the context of justification."

"Good criticism is the one that helps us improve."

"Thinking is not an activity very many people wish to do."

"The growth of knowledge is the discovery of our ignorance."

"Darwinism is not a testable scientific theory."

"Time is precious because it is finite."

"The future is not written; it is open."

"I may be wrong and you may be right, and by an effort we may get nearer the truth."

"Optimism is the foundation of every successful endeavor."

"Education is not the filling of a pail, but the lighting of a fire."

"The pursuit of truth is the noblest of all endeavors."

"Life is problem-solving in action."

"We should be as generous as possible in interpreting the words of others."

"The greatest threat to freedom is a convinced majority."

"Change is the only constant in life."

"Science is not sacred."

"Every problem creates an opportunity."

"The best books are treasuries of good words and good thoughts."

"Imagination is more important than knowledge."

"We are all responsible for our actions."

"Peace cannot be achieved through force."

"The more we try to perfect ourselves, the more we realize how imperfect we are."

"Good political institutions are not enough."

"We learn best through dialogue and debate."

"History is not a prison; it is a guide."

"Mistakes are the stepping stones to success."

"The unexamined life is not worth living."

"Creativity requires the courage to fail."