Werner Heisenberg was a German physicist who developed the theory of quantum mechanics and who wrote Physics and Philosophy.

Quotes by Werner Heisenberg in Time One

theory for which the fundamental physical and mathematical hypotheses are no longer susceptible of modification.

[T]he change in the concept of reality manifesting itself in quantum theory is not simply a continuation of the past; it seems to be a real break in the structure of modern science.

The probability function can be connected with reality only if one essential condition is fulfilled: if a new measurement is made to determine a certain property of the system. Only then does the probability function allow us to calculate the probable result of the new measurement

Quite generally there is no way of describing what happens between two consecutive observations. It is of course tempting to say that the electron must have been somewhere between the two observations and that therefore the electron must have described some kind of path or orbit even if it may be impossible to know which path. This would be a reasonable argument in classical physics. But in quantum theory it would be a misuse of language which … cannot be justified.

The incomplete knowledge of a system must be an essential part of every formulation in quantum theory.

A whole new field of reality was found, altogether beyond the appreciation of the Middle Ages during which supernatural revelation was the centre of all thought.

Perhaps it is not too rash to hope that new spiritual forces will again bring us nearer to the unity of a scientific concept of the universe which has been so threatened during the last decades.

Perhaps there [is] no such thing as an indivisible particle.

[A]n intensive study of all questions concerning the interpretation of quantum theory in Copenhagen finally led to a complete and, as many physicists believe, satisfactory clarification of the situation. But it was not a solution which one could easily accept. I remember discussions with Bohr which went through many hours till very late at night and ended almost in despair; and when at the end of the discussion I went alone for a walk in the neighboring park I repeated to myself again and again the question: Can nature possibly be as absurd

[I]n the history of human thinking the most fruitful developments frequently take place at those points where two different lines of thought meet. These lines may have their roots in quite different parts of human culture, in different times or different cultural environments or different religious traditions ….

[O]ne would get into hopeless difficulties if one tried to describe what happens between two consecutive observations.

Their vision is to… influence … the research of the following century.