Only a life lived for others is a life worthwhile.

Imagination is everything. It is the preview of life's coming attractions.

I refuse to make money out of my science. My laurel is not for sale like so many bales of cotton.

[Asked about a book in which 100 Nazi professors charged him with scientific error.] Were I wrong, one professor would have been quite enough.

Nature conceals her secrets because she is sublime, not because she is a trickster.

(Reply on what constitutes scientific proof:)"The question is much too difficult for me.

I am a determinist. As such, I do not believe in free will. The Jews believe in free will. They believe that man shapes his own life. I reject that doctrine philosophically. In that respect I am not a Jew.