A physicist visits a colleague and notices a horseshoe hanging on the wall above the entrance. 'Do you really believe that a horseshoe brings luck?' he asks. 'No,' replies the colleague, 'but I've been told that it works even if you don't believe in it.'

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

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

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

The present state of atomic theory is characterized by the fact that we not only believe the existence of atoms to be proved beyond a doubt, but also we even believe that we have an intimate knowledge of the constituents of the individual atoms.

One must always do what one really cannot.

It is the hallmark of any deep truth that its negation is also a deep truth.