New ideas are not only the enemies of old ones; they also appear often in an extremely unacceptable form.

It is really the mistake of our age. We think it is enough to discover new things, but we don't realize that knowing more demands a cor­responding development of morality.

One could say, with a little exaggeration, that the persona is that which in reality one is not, but which oneself as well as others think one is.

Life really does begin at forty. Up until then, you are just doing research.

Fortunately, in her kindness and patience, Nature has never put the fatal question as to the meaning of their lives into the mouths of most people. And where no one asks, no one needs to answer.

Dreams are the facts from which we must proceed.

Naturally, every age thinks that all ages before it were prejudiced, and today we think this more than ever and are just as wrong as all previous ages that thought so. How often have we not seen the truth condemned! It is sad but unfortunately true that man learns nothing from history.