One thought spectra are marvellous, but it is not possible to make progress there. Just as if you have the wing of a butterfly then certainly it is very regular with the colors and so on, but nobody thought one could get the basis of biology from the coloring of the wing of a butterfly.

A person who wasn't outraged on first hearing about quantum theory didn't understand what had been said.

The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness.

When searching for harmony in life one must never forget that in the drama of existence we are ourselves both actors and spectators.

Of course I don't believe in it [pointing to horseshoe on his office wall]. But I understand that it brings you luck whether you believe in it or not.

Anyone not shocked by quantum mechanics has not yet understood it.

When asked ... [about] 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.'