[About describing atomic models in the language of classical physics:]We must be clear that when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned...

Prediction is very difficult, especially about the future.

Every sentence I utter must be understood not as an affirmation but as a question.[A caution he gives his students, to be wary of dogmatism.]

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.

Never express yourself more clearly than you are able to think.

There are trivial truths and there are great truths. The opposite of a trivial truth is plainly false. The opposite of a great truth is also true.

An expert is a person who has made all the mistakes that can be made in a very narrow field.

You can recognize a small truth because its opposite is a falsehood. The opposite of a great truth is another truth.

How wonderful that we have met with a paradox. Now we have some hope of making progress.

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

Your theory is crazy, but it’s not crazy enough to be true.

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

[About the great synthesis of atomic physics in the 1920s]It was a heroic time. It was not the doing of any one man; it involved the collaboration of scores of scientists from many different lands....

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...

I myself find the division of the world into an objective and a subjective side much too arbitrary. The fact that religions through the ages have spoken in images, parables, and paradoxes means simply that...

It is not enough to be wrong, one must also be polite.

The meaning of life consists in the fact that it makes no sense to say that life has no meaning.