总统的职位是伟大的，但担任这个职位的人并不伟大。
The office of President is great, but the man who holds it is not.
The natural and moral world is the two-fold object of man's rational care.
数学不是一项观赏性运动。你必须亲自去做才能理解它。
As to the gods, I do not know whether they exist or not, or what they are like.
Graceful silence speaks more profoundly than empty words.