The very nature of the quantum theory ... forces us to regard the space-time coordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and description, respectively.

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

You must come to Copenhagen to work with us. We like people who can actually perform thought experiments!

Sometimes the child in one behaves a certain way and the rest of oneself follows behind, slowly shaking its head.

The old saying of the two kinds of truth. To the one kind belongs statements so simple and clear that the opposite assertion obviously could not be defended. The other kind, the so-called 'deep truths', are statements in which the opposite also contains deep truth.

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.

In our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold aspects of our experience.