Ignorant men raise questions that wise men answered a thousand years ago.

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.

Only the heart without a stain knows ease.

Man is not born to solve the problem of the universe, but to find out what he has to do; and to restrain himself within the limits of his comprehension.

It is a great pleasure to transport one's-self into the spirit of the times; to see how a wise man has thought before us, and to what a glorious height we have at last carried it.

The older I get the more I trust in the law according to which the rose and the lily bloom.

Whether one show one's self a man of genius in science or compose a song, the only point is, whether the thought, the discovery, the deed, is living and can live on.