Popper, Karl

"The true paradox is only the paradox that is true."

"I may not be smarter than you, but I can admit when I'm wrong."

"The more we learn about the world, and the deeper our learning, the more conscious, clear and definite will be our knowledge of what we do not know."

"Science may be described as the art of systematic over-simplification."

"Criticism of my views is welcome. What is not welcome is ignorance."

"We are not interested in the prospects of happiness; they do not interest us."

"The task is not so much to see what no one has yet seen, but to think what nobody has yet thought about that which everybody sees."

"One can never be sure of anything."

"The pursuit of truth is more valuable than the possession of it."

"Optimism is an intellectual choice."

"I have always fought for ideas—that's what I was made for."

"Happiness cannot be a serious political aim. It is not a fit aim for either a man or a state."

"Change and growth take place when a person has risked himself and dares to become involved with other people and new experiences."

"The future is completely open. Everything can still happen."

"I am an idealist. I believe in the power of ideas."

"There is no history of mankind, there are only many histories of all kinds of aspects of human life."

"We do not learn from history because we do not learn the right lessons."

"Freedom is not freedom from constraint, but freedom to act within constraints."

"The most important aspect of freedom is freedom from fear."

"Peace is not something you wish for; it is something you make, something you do, something you are, and something you give."

"The beautiful thing about learning is that no one can take it away from you."

"I am against all ideologies. I am for the open society."

"Nature is not something that can be conquered."

"All life is problem-solving."

"We must stand on our own two feet and fend for ourselves."

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

"There can be no ultimate standards. There is no truth in the absolute sense."

"I am a rationalist, but not a naïve rationalist."

"Science begins with myths, and the examination of old myths."

"The poverty of historicism, as I call it, is the belief that we can predict the future."