就陰陽和道體的關係，分析船山對「一陰一陽之謂道」的解釋，是把陰陽之氣當作道體。本文指出道就是陰陽之氣全體，道和陰陽相與為體。之所以不言「陰陽之謂道」，而要加上兩個「一」字，是為了強調道為陰陽自具的主持精粹之用，一之一之正是指道的主宰義。道和陰「統此一物」，然各有不同意指，是以分立兩名。船山之說的目的，是了充實他以氣為宇宙本體的理論之內容。

　　　　　To analyze Wang's interpretation of “Dao made of one Ying and one Yang” in terms of the relationship between Ying-yang and the entity of Dao is regarding the Qi of Ying and Yang as the entity of Dao. In this paper, we intend to show that Dao is the Qi of Ying and Yang and that Dao and Ying-yang is united as an entity. The reason why it is “Dao made of one Ying and one Yang” rather than “Dao made of Ying and Yang” is to emphasize the Dao is the essence of Ying and Yang, and “one” is the principal meaning of Dao. Dao and Ying-yang are basically the same but interpreted differently and therefore separated. Wang's doctrine is to substantiate his theory with Qi as the entity of the universe.