The great moral teachers of humanity were in a way artistic geniuses in the art of living.

I am neither especially clever nor especially gifted. I am only very, very curious.

No fairer destiny could be allotted to any physical theory than that it should of itself point out the way to the introduction of a more comprehensive theory, in which it lives on as a limiting case.

A man has to work so hard so that something of his personality stays alive. A tomcat has it so easy, he has only to spray and his presence is there for years on rainy days.

One should not pursue goals that are easily achieved. One must develop an instinct for what one can just barely achieve through one’s greatest efforts.

The aim (of education) must be the training of independently acting and thinking individuals who, however, see in the service to the community their highest life problem.

I have remained a simple fellow who asks nothing of the world; only my youth is gone - the enchanting youth that forever walks on air.