My only refuge, as a serious young man, from the despair of my financial burden to my family, is that I did everything I could to never permit myself any amusements or diversions except those afforded by my studies.

My internal and external life depend so much on the work of others that I must make an extreme effort to give as much as I receive.

A forced faithfulness is a bitter fruit for all concerned.

My opinion about Miller's experiments is the following. ... Should the positive result be confirmed, then the special theory of relativity and with it the general theory of relativity, in its current form, would be invalid. Experimentum summus judex. Only the equivalence of inertia and gravitation would remain, however, they would have to lead to a significantly different theory.

You cannot prevent and prepare for war at the same time.

This is what the painter, the poet, the speculative philosopher, and the natural scientists do, each in his own fashion.

A permanent peace cannot be prepared by threats but only by the honest attempt to create a mutual trust. However strong national armaments may be, they do not create military security for any nation nor do they guarantee the maintenance of peace.