Karl Popper

"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."

"All life is problem solving."

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

"The more you know, the more you realize you know nothing."

"True ignorance is not the absence of knowledge, but the refusal to acquire it."

"We are not makers of history. We are made by history."

"The problems we face today cannot be solved by the same level of thinking that created them."

"Creativity comes before analysis."

"I have never been a scientist in the usual sense, but I have been interested in questions."

"Critical thinking is the ability to think clearly and rationally."

"We learn through our mistakes."

"The future is open. It is not predetermined."

"Man is not a rational animal; he is a rationalizing animal."

"There are no final answers."

"The sources of knowledge are many, but they all flow into the same river of understanding."

"Courage is not the absence of fear, but the triumph over it."

"In the last analysis, we do not refute our predecessors, we add to our knowledge."

"Freedom is the freedom to say that two plus two make four."

"Every day I try to do something useful."

"It is impossible to speak in such a way that you cannot be misunderstood."

"Violence is always a confession of ultimate inarticulate."

"A theory that cannot be criticized is not a good theory."

"Open society is one which allows criticism and change."

"We are all mistaken sometimes; only the wise admit it."

"The most important thing in the search for truth is not to find it, but to be ready for it."

"I have learned more from my mistakes than my successes."

"The best way to understand something is to try to change it."

"Nature is not deterministic."

"Beauty and truth are not always the same thing."

"Our knowledge is a drop; our ignorance is an ocean."