Keep your face always toward the sunshine—and shadows will fall behind you.

In republican governments, men are all equal; equal they are also in despotic governments: in the former, because they are everything; in the latter, because they are nothing.

质量胜过数量。

I'm not a person who lives in the past.

我们现代的头骨里装着一个石器时代的心智。

在学习结束时，我们知道物理学的所有过去，但对现在和未来一无所知。