What is Taiyi 太一 in Taoism?

Taiyi belongs to the category of ancient philosophy. In ancient China, "Tai" was also written as "Da" (great) or "Tai" (peace), and "Yi" (one) was sometimes written as "Yi" (the second of the ten Heavenly Stems). "Tai" denotes the first and the highest, while "Yi" signifies the unique, unopposed, and undifferentiated unity.

Zhuangzi·Tianxia states that Laozi's doctrine "takes Taiyi as its foundation". Here, "Taiyi" refers to what Lao, "Taiyi" refers to what Laozi called "Dao" (the Way), also known as "Wu" (non-being). In * Lüshi Chunqiu* (Master Lü's Spring and Autumn Annals), "Taiyi" denotes the material origin of the world. Lüshi Chunqiu·Dayue (Great Music) says: "The Dao is the most refined; it cannot be shaped, cannot be named. If we must reluctantly give it a name, we call it Taiyi." This "most refined" Dao or Taiyi is also "Jingqi" (essential qi), i.e., the fine primitive substance.

In The Book of Rites, Taiyi also refers to the primordial qi. The Book of Rites·Liyun (On the Operations of Rites) states: "Rites must originate from Taiyi; it divides into heaven and earth, transforms into yin and yang, changes into the four seasons, and manifests as ghosts and spirits." Kong Yingda, a renowned Confucian scholar of the Tang Dynasty, believed that "Dayi" (Great One) here is "Taiyi", and "must originate from Taiyi" refers to the primal qi in the undifferentiated chaos before heaven and earth separated.

The proposal of the category "Taiyi" reflects ancient Chinese philosophers' understanding of the unity of the world and the process of things developing from simplicity to complexity, and from lower to higher levels.