All the fifty years of conscious brooding have brought me no closer to answer the question, "What are light quanta?" Of course today every rascal thinks he knows the answer, but he is deluding himself.

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.

It is difficult even to attach a precise meaning to the term "scientific truth." So different is the meaning of the word "truth" according to whether we are dealing with a fact of experience, a mathematical proposition or a scientific theory. "Religious truth" conveys nothing clear to me at all.

There is, however, a somber point in the social outlook of Americans. Their sense of equality and human dignity is mainly limited to people of white skin.... The more I feel like an American, the more the situation pains me.

Marriage is but slavery made to appear civilized.

The true definition of madness is repeating the same action, over and over, hoping for a different result.

Not until the creation and maintenance of decent conditions of life for all men are recognized and accepted as a common obligation of all men and all countries — not until then shall we, with a certain degree of justification, be able to speak of mankind as civilized.