One is never satisfied with a portrait of persons whom one knows. That is why I have always pitied portraitists. One demands so seldom of others the impossible, but demands just that of the portraitists.

Difficulties increase the nearer we get to the goal.

All the knowledge I possess everyone else can acquire, but my heart is all my own.

Whatever necessity lays upon thee, endure; whatever she commands, do.

Normally, people believe that, if they hear just words, that these words must lead to some thought.

Our friends show us what we can do; our enemies teach us what we must do.

Errors belong to libraries; truth, to the human mind.