Man... knows only when he is satisfied and when he suffers, and only his sufferings and his satisfactions instruct him concerning himself, teach him what to seek and what to avoid. For the rest, man is a confused creature; he knows not whence he comes or whither he goes, he knows little of the world, and above all, he knows little of himself.

A person places themselves on a level with the ones they praise.

At the end of life thoughts hitherto impossible come to the collected mind, like good spirits which let themselves down from the shining heights of the past.

Die Mathematiker sind eine Art Franzosen. Spricht man zu ihnen, so übersetzen sie alles in ihre eigene Sprache, und so wird es alsobald etwas ganz anderes. Mathematicians are a kind of Frenchmen. Whenever you say anything or talk to them, they translate it into their own language, and right away it is something completely different.

The use of a thing is only a part of its significance. To know anything thoroughly, to have the full command of it in all its appliances, we must study it on its own account, independently of any special application.

Religion is not in want of art; it rests on its own majesty.

The spirit from which we act is the principal matter.