You train yourself in the art of being mysterious to everyone. My dear friend! What if there were no one, who cared about guessing your riddle, what pleasure would you then take in it?

The conclusions of passion are the only reliable ones.

You love the accidental. A smile from a pretty girl in an interesting situation, a stolen glance, that is what you are hunting for, that is a motif for your aimless fantasy. You who always pride yourself on being an observateur must, in return, put up with becoming an object of observation. Ah, you are a strange fellow, one moment a child, the next an old man; one moment you are thinking most earnestly about the most important scholarly problems, how you will devote your life to them, and the next you are a lovesick fool. But you are a long way from marriage.

I divide my time as follows: half the time I sleep, the other half I dream. I never dream when I sleep, for that would be a pity, for sleeping is the highest accomplishment of genius.

Genius never desires what does not exist.

Old age realizes the dreams of youth: look at Dean Swift; in his youth he built an asylum for the insane, in his old age he was himself an inmate.

All essential knowledge relates to existence, or only such knowledge as has an essential relationship to existence is essential knowledge.