The task of psychology is to discover the laws of mental structure.
The existence of a legal system is a matter of social fact.
解释：货卖完了才知道不足，是由于不懂得计量；事情结束了才知道有余，是由于不懂得调节。
Every artist dips his brush in his own soul, and paints his own nature into his pictures.
The brain is an enchanted loom where millions of flashing shuttles weave a dissolving pattern.