The term represents a world outlook and a way of thinking which hold that heaven and earth and man are interconnected. This world outlook emphasizes the integration and inherent relationship between heaven, earth, and man. It highlights the fundamental significance of nature to man or human affairs, and describes the endeavor made by man to pursue life, order, and values through interaction with nature. The term has different ways of expression in history, such as heaven and man are of the same category, sharing the same vital energy, or sharing the same principles. Mencius（372？-289 BC）, for one, believed that through mental reflection one could gain understanding of human nature and heaven, emphasizing the unity of mind, human nature, and heaven. Confucian scholars of the Song Dynasty sought to connect the principles of heaven, human nature, and the human mind. Laozi maintained that “man’s law is earthly, earth’s law is natural, and heaven’s law is dao.” Depending on a different understanding of heaven and man, the term may have different meanings.

In terms of integration of categories, heaven and man are one. (Dong Zhongshu: Luxuriant Gems of The Spring and Autumn Annals)

A Confucian scholar is sincere because of his understanding, and he achieves understanding because of his sincerity. That is why heaven and man are united as one. One can become a sage through studies, and master heaven’s law without losing understanding of man’s law. (Zhang Zai: Enlightenment Through Confucian Teachings)