Werner Heisenberg

"The positivists have a simple solution: the world must be divided into that which we can say clearly and the rest, which we must pass over in silence."

"I am now convinced that theoretical physics is actual philosophy."

"The true sign of intelligence is not knowledge but imagination."

"In mathematics you don't understand things. You just get used to them."

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

"Man can embody truth, but he cannot know it."

"Uncertainty is inherent in the nature of the universe itself."

"The violent reaction on the recent development of modern science can only be understood when one realizes that here the very foundations of the faith in reason are at stake."

"What is the world made of? We have found that it is not made of material substance. The stuff of the world is mind-stuff."

"Every physics student knows what is meant by the 'Uncertainty Principle'."

"The idea of objective reality has evaporated not only from quantum mechanics but also from relativity theory."

"Religion is the area of human experience where people come up against the infinite."

"I have always found it of paramount importance to listen carefully to what the other fellow has to say before making a reply."

"Science as a whole has become so complicated that it is hard for any individual to grasp all of it."

"A new scientific truth does not triumph by convincing its opponents, but rather because its opponents eventually die."

"The atoms or elementary particles themselves are not real; they form a world of potentialities."

"What can be said at all can be said clearly."

"The first principle of ethics is the recognition of every human being's absolute value."

"If I understand the question, I shall answer it; if I do not, I shall say so."

"Beauty is the conformity of the parts to each other and to the whole."

"The aim of science is not to open the door to infinite wisdom, but to set a limit to infinite error."

"One of the most important features of quantum theory is its description of the complementarity of physical properties."

"The idea that we can describe nature in an objective fashion that is independent of the observer is losing credibility."

"Whoever undertakes to set himself up as a judge of truth and knowledge is shipwrecked by the laughter of the gods."

"The first step toward improvement in any field is the clear recognition of the current situation."

"What is hard for us to understand today is that the natural philosophers had a much broader view of their subject than modern scientists have."

"The hope that new experimental discoveries will rescue us from the embarrassment of the present situation is probably a vain one."

"Nothing can be said about nature without speaking of matter and at the same time of form."

"It is the tension between creativity and skepticism that has produced the stunning and unexpected findings of science."

"The difficulty of quantum mechanics lies not in the difficulty of the theory itself, but in the difficulty of abandoning old modes of thought."