The only mistake in life is the lesson not learned.

Even a fool is wise after an event.

When forced to summarize the general theory of relativity in one sentence: Time and space and gravitation have no separate existence from matter.

Time and space are not conditions of existence, time and space is a model for thinking

What is this frog and mouse battle among the mathematicians?

Why does this magnificent applied science which saves work and makes life easier bring us so little happiness? ... The simple answer runs: 'Because we have not yet learned to make sensible use of it.'

With all my heart I believe that the world's present system of sovereign nations can only lead to barbarism, war and inhumanity, and that only world law can assure progress towards a civilized peaceful community.