Quotes from Werner Karl Heisenberg

Every tool carries with it the spirit by which it has been created.

Since the measuring device has been constructed by the observer… we have to remember that what we observe is not nature in itself but nature exposed to our method of questioning.

The more precisely we determine the position [of an electron], the more imprecise is the determination of velocity at this instant, and vice versa.

Whenever we proceed from the known into the unknown we may hope to understand, but we may have to learn at the same time a new meaning of the word 'understanding.