Werner Heisenberg

The act of observation plays a decisive role in the event and... the reality varies, depending upon whether we observe it or not.

The laws of nature which we formulate mathematically in quantum theory deal no longer with the particles themselves but with our knowledge of the elementary particles.

The atomic physicist has had to resign himself to the fact that his science is but a link in the infinite chain of man's argument with nature, and that it cannot simply speak of nature 'in itself'.

The unity of science may be hidden, but it is real.

The problems of society are not solved by technology alone.

We have to be clear that when it comes to atoms, language can be used only as in poetry.

The discontinuous change in the wave function takes place with the act of registration of the result by the mind of the observer.

The common division of the world into subject and object, inner world and outer world, body and soul, is no longer adequate.

The electron is no longer considered as a particle in the classical sense of the word.

In the experiments about atomic events we have to do with things and facts, with phenomena that are just as real as any phenomena in daily life. But the atoms or the elementary particles themselves are not as real; they form a world of potentialities or possibilities rather than one of things or facts.

The hope that new experiments will lead us back to objective events in time and space is about as well founded as the hope of discovering the end of the world in the unexplored regions of the Antarctic.

The aim of research is the discovery of the equations which the field quantities satisfy.

The physicist thus finds himself in a world from which the bottom has dropped clean out.

The final analysis of the process of observation in atomic physics has led to the conclusion that the laws of nature which we formulate mathematically in quantum theory deal no longer with the elementary particles themselves but with our knowledge of them.

The energy of a system is not defined more accurately than within the limits given by the uncertainty relation.

The path comes into existence only when we observe it.

We can no longer speak of the behavior of the particle independently of the process of observation.

The scientific method of analysing, explaining, and classifying has become conscious of its limitations.

The world thus appears as a complicated tissue of events, in which connections of different kinds alternate or overlap or combine and thereby determine the texture of the whole.

The concept of 'understanding' loses its meaning when applied to the elementary particles.