Relativity teaches us the connection between the different descriptions of one and the same reality.

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.

In the middle of every difficulty lies opportunity.

... 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.

Games are the most elevated form of investigation.

This is too difficult for a mathematician. It takes a philosopher. The hardest thing in the world to understand is the income tax.

The music of Mozart is of such purity and beauty that one feels he merely found it - that it has always existed as part of the inner beauty of the universe waiting to be revealed.