The world is a great play, and we are the actors.

幸福不是现成的东西，它来自你自己的行动。

The present state of the system of nature is evidently a consequence of what it was in the preceding moment, and if we conceive of an intelligence which at a given instant comprehends all the relations of the entities of this universe, it could state the respective positions, motions, and general effects of all these entities at any time in the past or future.

不要为变老而遗憾。这是许多人求之不得的特权。