What is the Primordial Simplicity in Taoism? 什么是太素

It refers to the state or stage where all principles of heaven and earth have taken on form and substance yet not developed into complete entities.

Liezi·Tian Ruo states: "Taisu is the origin of substance." It means Taisu marks the beginning of all things possessing both form and substance. Bai Hu Tong·Heaven and Earth records: "For the primordial heaven at its inception, there was first Taichu, then Taishi; when form and omen were fully formed, it was named Taisu."

Taoism interprets Taisu with a meaning essentially consistent with that of predecessors. For example, Qian Yuan Zi's Treatise on the Three Beginnings says: "Taisu is the origin of substance, where both form and substance come to be named." Records of Emperors notes: "When form transforms and acquires substance, it is called Taisu." Volume 67 of Dao Fa Hui Yuan states: "Taisu is what Taishi transforms into and takes form; with form comes substance, yet no complete entity is formed—and this is named Taisu. Taisu is the origin of substance, where no complete entity has yet developed, an evolution driven by the movement of Qi and the interplay of Yin and Yang."