"The greatest obstacle to progress in science is the belief that one knows something which one does not know."

"The world is a mystery, and the more we learn, the more mysterious it becomes."

"The true meaning and purpose of human life lies in our striving for understanding and knowledge."

"The reason why our sentient, percipient and thinking ego is met nowhere within our scientific world picture can easily be indicated in seven words: because it is itself that world picture."

"The number of children born to a marriage ought to be limited, and that a man who has already had some children should be sterilized."