Each act is an island in time, to be judged on its own.

That which is impenetrable to us really exists. Behind the secrets of nature remains something subtle, intangible, and inexplicable. Veneration for this force beyond anything that we can comprehend is my religion.

We come now to the question: what is a priori certain or necessary, respectively in geometry (doctrine of space) or its foundations? Formerly we thought everything; nowadays we think nothing. Already the distance-concept is logically arbitrary; there need be no things that correspond to it, even approximately.

What is essential in the life of a man of my kind is what he thinks and how he thinks, and not what he does or suffers.

I believe that we don't need to worry about what happens after this life, as long as we do our duty here-to love and to serve.

Learning is experience. Everything else is just information.

Striving for peace and preparing for war are incompatible with each other, and in our time more so than ever.