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.

When we see the many grave-stones which have fallen in, which have been defaced by the footsteps of the congregation, which lie buried under the ruins of the churches, that have themselves crumbled together over them; we may fancy the life after death to be as a second life, into which man enters in the figure, or the picture or the inscription, and lives longer there than when he was really alive. But this figure also, this second existence, dies out too, sooner or later. Time will not allow himself to be cheated of his rights with the monuments of men or with themselves.

Enjoy when you can, and endure when you must.

Courage is the commitment to begin without any guarantee of success.

Time flies, and what is past is done.

What we don't understand we don't possess.

There is no permanence in doubt; it incites the mind to closer inquiry and experiment, from which, if rightly managed, certainty proceeds, and in this alone can man find thorough satisfaction.