An old saying goes: "Those who seek the upper part will get it; those who seek the lower part will get it; those who seek the lower part will get nothing." The Analects of Confucius: "If you seek the upper part, you will get it; if you seek the lower part, you will get nothing." If you seek what is below, you will gain nothing."

"The Art of War" also says: "Seek what is above, and you will get what is below; if you seek what is below, you will get what is below; if you seek what is below, you will get it. Defeat."

Volume 4 of Emperor Taizong of the Tang Dynasty: "If you take the method from above, you can only get the middle; if you take the method from the middle, it will be the bottom."

At the end of the Song Dynasty and the beginning of the Yuan Dynasty. Yan Yu, a poetry critic during the period, said in his "Canglang Poetry Talk": "If you learn from the top, you can only get the middle; if you learn from the top, you will get the lowest.