What is hardest of all? That which seems most simple: to see with your eyes what is before your eyes.

Nature understands no jesting. She is always true, always serious, always severe. She is always right, and the errors are always those of man.

An absent friend gives us friendly company when we are well assured of his happiness.

Who can think wise or stupid things at all that were not thought already in the past.

Science and art belong to the whole world, and before them vanish the barriers of nationality.

One can stand anything except a succession of ordinary days

There is not a single outward mark of courtesy that does not have a deep moral basis.