每个人都有不为世人所知的秘密悲伤；很多时候，我们称一个人冷漠，而他只是悲伤。
"Every man has his secret sorrows which the world knows not; and often times we call a man cold when he is only sad."
The most profound discoveries often come from the simplest observations.
It is not the benevolence of the employer that determines the wages of labor， but the competition among employers.
顾客永远是对的，即使他们是错的。