We must learn to see the world anew.

It is only men who are free, who create the inventions and intellectual works which to us moderns make life worth while.

However we select from nature a complex [of phenomena] using the criterion of simplicity, in no case will its theoretical treatment turn out to be forever appropriate (sufficient).... I do not doubt that the day will come when [general relativity], too, will have to yield to another one, for reasons which at present we do not yet surmise. I believe that this process of deepening theory has no limits.

My scientific work is motivated by an irresistible longing to understand the secrets of nature and by no other feeling. My love for justice and striving to contribute towards the improvement of human conditions are quite independent from my scientific interests.

Mere thinking cannot reveal to us the highest purpose.

The dog is very smart. He feels sorry for me because I receive so much mail; that's why he tries to bite the mailman.

It's not that I'm so smart, it's just that I stay with problems longer.