When asked whether the algorism of quantum mechanics could be considered as somehow mirroring an underlying quantum world, Bohr would answer, "There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature." Bohr felt that every step in the development of physics has strengthened the view that the problem of establishing an unambiguous description of nature has only one solution. He regarded all attempts to replace our elementary concepts or to introduce a new logic to account for the peculiarities of quantum phenomena as not merely unnecessary but also incompatible with our most fundamental conditions, since we are suspended in a unique language.

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 neighbouring park I repeated to myself again and again the question: Can nature possibly be so absurd as it seemed to us in these atomic experiments?

Not often in life has a human being caused me such joy by his mere presence as you did.

If quantum theory has any philosophical importance at all, it lies in the fact that it demonstrates for a single, sharply defined science the necessity of dual aspects and complementary considerations. Niels Bohr has discussed this question with respect to many applications in physiology, psychology, and philosophy in general.

One of the favorite maxims of my father was the distinction between the two sorts of truths, profound truths recognized by the fact that the opposite is also a profound truth, in contrast to trivialities where opposites are obviously absurd.

Everything we call real is made of things that cannot be regarded as real.

Of course not ... but I am told it works even if you don't believe in it.

Stop telling God what to do with his dice.

Prediction is very difficult, especially about the future.

Anyone who is not shocked by quantum theory has not understood it.