... on principle, it is quite wrong to try founding a theory on observable magnitudes alone. In reality the very opposite happens. It is the theory which decides what we can observe.

All the fifty years of conscious brooding have brought me no closer to answer the question, "What are light quanta?" Of course today every rascal thinks he knows the answer, but he is deluding himself.

They come into being not through demonstration but through revelation, through the medium of powerful personalities.

Everyone should be respected as an individual, but no one idolized.

Warfare cannot be humanized.

For science can only ascertain what is, but not what should be, and outside of its domain value judgments of all kinds remain necessary. Religion, on the other hand, deals only with evaluations of human thought and action: it cannot justifiably speak of facts and relationships between facts.

No problem is ever solved in the same consciousness thas was used to create it.