Abstract:In the history of interpreting The Doctrine of the Mean, the concept of “Zhong He (中和)” has been pivotal in understanding the text. Cheng Yi and Zhu Xi, two significant figures in this discourse, approached the concept from their philosophical perspectives. Central to their views is the question of the human psyche’s state when emotional thoughts are not yet visible, and whether and how one can experience the Tao in the mental stage before emotions and thoughts emerge. When Cheng interpreted “Zhong He”, he sought to distinguish his views from those of Buddhism and opposed using “stillness” to understand the mental stage before emotions and thoughts emerge. Furthermore, Cheng Yi also disagreed with the notion that one should seek the Tao by reaching this mental stage. He argued that this view of human psychology, though popular, was too similar to the theories of Buddhism and Taoism. His disagreements with Lü Dalin about “Zhong” can be interpreted in this light. According to Cheng, when emotions and thoughts are temporarily suspended, the human heart is not completely still, and the inclination towards emotional activity remains present. The stage of human mental activity referred to as “Wei Fa (未发)” is not mystical but rather a natural process. The term “Zhong” used to describe “Wei Fa” should be interpreted to mean impartial, without bias, and not possessing any mysterious connotations. With this understanding of “Zhong” as a premise, there is no apparent connection between “Zhong” and “He” in terms of substance and function. Cheng Yi believed that the Tao is always present in the human mental activity, regardless of whether emotions and thoughts have emerged or not. However, the Tao does not manifest itself at any particular mental stage. When emotions and thoughts arise, the Tao is undoubtedly present within them, and when emotions and thoughts do not emerge, the Tao remains in a state of “invisibility”. Zhu Xi believed that Cheng Yi had modified his statement, which requires a re-examination within the context of Cheng’s literary works. This interpretation of Cheng’s views may be Zhu’s personal opinion and not necessarily aligned with the actual state of Cheng’s thoughts. Therefore, it is essential to reconsider whether “ji ran bu dong, gan er sui tong (寂然不动,感而遂通)” is applicable to “Zhong” and “He”. “Ji ran bu dong, gan er sui tong” has a specific meaning in Cheng’s thought and has not been used to describe “Zhong” and “He”. The discourse on the issue of “Zhong He” in Lun Zhong Shu should be understood separately from the text of the note. When Zhu Xi discussed “Zhong He”, he faced even more complex theoretical challenges. The concept of “Zhong He” describes the inner being of human beings, which must distinguish itself from Buddhism on the one hand while also allowing individuals to experience the Tao in “Zhong He” on the other. In the first stage of his thought, Zhu Xi inherited Cheng Yi’s views, although there were some differences between the two in their interpretation of specific terms. In the second stage of his thought, Zhu completed the reconstruction of Cheng’s doctrine based on his inheritance of Cheng’s thought. Zhu established a relationship between the substance and function of “Zhong” and “He”. He also believed that individuals can experience the Tao even when emotions and thoughts are not yet developed. Through Zhu’s inheritance and development of Cheng’s theory, Neo-Confucianism’s doctrine about the human heart became more refined and complex.