Werner Heisenberg, Physics and Philosophy: The Revolution in Modern Science

"Here the attention of the research workers is primarily directed to the problem of reconciling the claims of the special relativity theory with those of the quantum theory. The extraordinary advances made in this field by Dirac ... leave open the question whether it will be possible to satisfy the claims of the two theories without at the same time determining the Sommerfeld fine-structure constant."

"Whenever we proceed from the known into the unknown we may hope to understand, but we may have to learn at the same time a new meaning of the word 'understanding."

"Whether we like it or not, modern ways are going to alter and in part destroy traditional customs and values."