We come now to the question: what is a priori certain or necessary, respectively in geometry (doctrine of space) or its foundations? Formerly we thought everything; nowadays we think nothing. Already the distance-concept is logically arbitrary; there need be no things that correspond to it, even approximately.

Fantasie is belangrijker dan kennis, want kennis is begrensd.

The same thinking and actions that created our problems cannot be used to solve them.

Galileo had already made a significant beginning toward a knowledge of the law of motion. He discovered the law of inertia and the law of bodies falling freely in the gravitational field of the earth.

I cannot conceive of a God who rewards and punishes his creatures, or has a will of the type of which we are conscious in ourselves. An individual who should survive his physical death is also beyond my comprehension, nor do I wish it otherwise; such notions are for the fears or absurd egoism of feeble souls.

Figuring out how to think about the problem.

The finest emotion of which we are capable is the mystic emotion.