I have little patience with scientists who take a board of wood, look for its thinnest part, and drill a great number of holes where drilling is easy.

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 pacifism is not based on any intellectual theory but on a deep antipathy to every form of cruelty and hatred.

Mankind must give up war in the Atomic Era. What is at stake is the life or death of humanity.

It almost seems to me that man was not born to be a carnivore.

Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.

I believe in Spinoza's God, who reveals Himself in the lawful harmony of the world, not in a God who concerns Himself with the fate and the doings of mankind... to Rabbi Herbert Goldstein (1929)