A legal system is a system of rules which are valid according to the system's own criteria of validity.

"All you have to do is write one true sentence. Write the truest sentence that you know."

科学不是形式逻辑——它需要思想的自由发挥，与其他任何创造性艺术一样。

这个世界惟有两样东西让我们的心灵感到深深的震撼，一是我们头顶上灿烂的星空,一是我们内心崇高的道德法则。

智慧是洞悉爱和争斗在宇宙中作用的关键。