Nothing happens until something moves.

If I give you a pfennig, you will be one pfennig richer and I'll be one pfennig poorer. But if I give you an idea, you will have a new idea, but I shall still have it too.

I do not believe in immortality of the individual, and I consider ethics to be an exclusively human concern with no superhuman authority behind it.

Things you can get access to, you should never memorize.

That is the way to learn the most, that when you are doing something with such enjoyment that you don't notice that the time passes.

Only a monomaniac gets anything done.

I believe that whatever we do or live for has its causality; it is good, however, that we cannot see through to it.