By examining Feng Youlan's series of philosophical works, the core of his philosophy of life is the theory of realm, the "four realms of life theory", especially the idea of ??"realm of heaven and earth", which is his important contribution to modern Chinese philosophy. . Examining Feng Youlan's lifelong research on the issue of "the realm of heaven and earth", Zhang Zai's "Xi Ming" and the thought of "people and things" are important sources of Feng Youlan's thoughts on the "realm of heaven and earth"; throughout Feng Youlan's academic activities throughout his life, in his academic career In different periods of his life, "Four Sentences of Hengqu" had a profound impact on his life ideals, academic beliefs and realm theory. Of course there are similarities. However, the relationship between people and things is Confucianism, while the realm of heaven and earth covers the three schools of thought: Confucianism, Buddhism, and Taoism. Zhang Zai's four sentences are what I call "Hengqu's Four Sentences". "Establish a heart for the heaven and earth, establish a destiny for the living and the people, carry on the unique knowledge for the past saints, and create peace for all generations." These four sentences briefly describe the characteristics of human beings. The reason why humans are human is that "the reason why humans are different from beasts" ". The subjects of the four words "wei" in these four sentences may be Zhang Zai himself, a philosopher, or philosophy. In any case, from an ordinary person's point of view, the first sentence, "Establish a heart for heaven and earth," is very confusing. In fact, it is not difficult to understand. There was an unknown poet in the Song Dynasty who wrote two poems on the wall of an inn: "If heaven did not give birth to Zhongni, the eternity would be as long as night." This is Confucius as the representative of human beings.