It means: you can't improve the taste of calligraphy without learning calligraphy from the Jin Dynasty.
"Books don't enter Jin, but they don't go to the class; Law is not king, it is one of the products. " In other words, it is impossible to improve the taste of calligraphy without starting from the Jin people; If you don't obey Wang Xizhi's statutes, you won't get the true meaning of calligraphy. Xiang Mu summed up this basic principle of calligraphy evaluation in Ming Dynasty, which was the ideal realm of calligraphy established by Li Shimin.