This passage comes from Book One of The Analects (Xue Er): "Master You said, 'In the practice of Li (Propriety/Ritual), harmony is the most valuable. The Way of the Former Kings achieved this beauty. In matters both great and small, follow this principle. Yet there are times when it cannot be followed. To know harmony and pursue harmony for its own sake, without regulating it with Li, is also not acceptable.'"
"Harmony (He)" is a particularly advocated ethical, political, and social principle in Confucianism. The Book of Rites (Liji) chapter "Doctrine of the Mean (Zhongyong)" states: "Before the feelings of pleasure, anger, sorrow, and joy are aroused, it is called centrality (zhong, the mean); when they are aroused and each attains its due measure and degree, it is called harmony (he)." Yang Yufu's "Annotations on The Analects (Lunyu Shuzheng)" writes: "When affairs attain their due measure and degree, they are all called harmony, not only the arousal of pleasure, anger, sorrow, and joy. 'Harmony' today means being suitable, appropriate, and hitting the mark just right." Youzi (a disciple of Confucius) believed that the implementation and application of Li (ritual propriety) should value harmony. However, emphasizing harmony in everything, or seeking harmony for its own sake without being constrained by Li, is also unworkable. This means that while observing the hierarchical distinctions prescribed by Li, people should avoid discord among themselves. The viewpoint proposed by Youzi is significant.
In the society of patriarchal feudalism, the distinctions and oppositions between different social ranks were strictly enforced, with boundaries that allowed absolutely no confusion. Those of higher rank displayed their authority through their own rituals and etiquette, while those of lower rank obeyed orders with fear and trepidation. However, by the Spring and Autumn Period, this social order began to break down, and incidents of ministers killing rulers or sons killing fathers had become common. In response, Youzi (a disciple of Confucius) proposed the principle that "harmony is most valuable" (Harmony is most precious.), with the aim of easing the tension and opposition between different ranks, preventing their complete rupture, and thus stabilizing the social order of the time.
But from a theoretical perspective, we also feel that Youzi (a disciple of Confucius) emphasized both that the application of Li (Propriety) values harmony as most precious, and that one cannot seek harmony for its own sake—it must be regulated by Li. This shows that the "harmony" advocated by Youzi was not a principle-less compromise, which has its reasonableness.