Karl Popper

"The quest for certainty blocks the search for meaning. Uncertainty is the only certainty there is, and knowing how to live with insecurity is the only security."

"Creativity is no mystical talent. It is a skill that can be learned and practiced like any other skill."

"Bad luck comes to everyone, but only cowards complain about it."

"The human spirit is the spark that animates the universe, but the mind that comprehends it is more wonderful still."

"I may not be right, but I am never in doubt. That is my method."

"One should as a rule respect public opinion in so far as is necessary to avoid starvation and to prevent oneself being driven into the street; but anything that goes beyond this is voluntary submission to an unnecessary tyranny."

"The growth of our knowledge is the result of a process closely resembling what Darwin called 'natural selection' - that is, the natural selection of hypotheses."

"To be a scientist you must have a taste for both rationality and objectivity, combined with imagination."

"Science is not authority. Science is a process of learning about nature that is open to criticism and revision."

"Do not try to appear wise to others; try to be wise within yourself."

"The task of the science of logic is the analysis of the method of science."

"If we never risked being absurd, no achievement could be made."

"True friends are those who will tell you what you don't want to hear but need to hear."

"We may have found a fundamental law that, if obeyed, would greatly reduce human suffering."

"The best thing for being sad is to learn something. That is the only thing that never fails."

"Open society is based on the idea that no one has the truth; everyone is fallible; we learn from one another."

"Beauty does not lie in form, but in the meaning we give it."

"The future is not determined. We are not passive observers. We can and do make a difference through our choices."

"Tolerance is not a natural virtue - it must be learned and practiced constantly."

"The ideas we hold today shape the world we will live in tomorrow."

"To understand a man, you must understand what he was trying to accomplish."

"There can be no theory of learning that does not place emphasis on the passionate interests of the learner."

"The market economy is not a system for making everybody rich, but for making everybody richer."

"If you wish to improve your arguments, you must seek not to win the debate, but to understand the truth."

"Experience is not simply observation; it is observation directed by theory."

"The true strength of a person lies in their ability to admit what they do not know."

"In the end, we do not choose our values; they choose us through our commitments."

"There is no greater joy than the joy of understanding something that was previously mysterious."

"The more honest we are about our ignorance, the closer we come to wisdom."

"To improve is to change; to be perfect is to change often."