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

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.

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

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

Humanity will... be confronted with dangers of unprecedented character unless, in due time, measures can be taken to forestall a disastrous competition in such formidable armaments and to establish an international control of the manufacture and use of the powerful materials.

Every description of natural processes must be based on ideas which have been introduced and defined by the classical theory.