Playfullness is the essential feature of productive thought.

The years of searching in the dark for a truth that one feels but cannot express, the intense desire and the alternations of confidence and misgiving until one breaks through to clarity and understanding, are known only to him who has experienced them himself.

For the most part, I do the thing which my own nature prompts me to do. It is embarrassing to earn so much respect and love for it.

It is only to the individual that a soul is given. And the high destiny of the individual is to serve rather than to rule, or to impose himself in any other way.

The most important method of education always has consisted of that in which the pupil was urged to actual performance.

From the viewpoint of a Jesuit priest I am, of course, and have always been an atheist.

The next world war will be fought with stones.