Cosmology
Qian, Kun, Kan, Li. The main cosmological emblems in the Cantong qi are Qian, Kun, Kan, and Li. Although these names belong to the vocabulary of the Book of Changes, in the Cantong qi they denote formless principles that serve to explicate how the Dao generates the world and manifests itself in it. The corresponding trigrams (Qian ☰, Kun ☷, Kan ☵, Li ☲) and hexagrams (Qian ䷀, Kun ䷁, Kan ䷜, Li ䷝) are symbolic forms used to represent those principles.
Qian is the active ("creative") principle, essence, Yang, and Heaven; Kun is the passive ("receptive") principle, substance, Yin, and Earth. Being permanently joined to one another in the precosmic domain, Qian entrusts its creative power to Kun, and Kun brings creation to accomplishment. In the everlasting instant in which Qian and Kun give birth to the cosmos, the Yang of Qian moves into Kun, and, in response, the Yin of Kun moves into Qian. In the symbolic representation by the corresponding trigrams, Qian ☰ entrusts its essence to Kun and becomes Li ☲; Kun ☷ receives the essence of Qian and becomes Kan ☵.
Kan and Li, therefore, replace Qian and Kun in the cosmic domain. Since they harbor the Yang of Qian and the Yin of Kun, respectively, as their own inner essences, they enable the Yin and Yang of the precosmic domain to operate in the cosmic domain. The main images of Qian and Kun are Heaven and Earth, which are immutably joined to one another. The main images of Kan and Li are the Moon and the Sun, which alternate in their growth and decline during the longer or shorter time cycles.
Five agents. The five agents (wuxing) are Wood, Fire, Soil, Metal, and Water. They are generated in the first place by the division of original Unity into Yin and Yang, and by the further subdivision of Yin and Yang into four states. In the Cantong qi, Water and Fire are the Yin and Yang of the postcelestial state, and Wood and Metal are True Yin and True Yang of the precelestial state. Soil, the fifth agent, has both a Yang and a Yin aspect. Being at the center, it stands for the source from which the other four agents derive.
Time Cycles. The cosmological portions of the Cantong qi give emphasis to three emblematic time cycles: the day, the month, and the year. These cycles manifest the presence of the One Breath (yiqi 一氣) of the Dao in the cosmos. All of them became models of the "fire times" (huohou 火候) in alchemy, which determine the process needed to heat the Elixir.
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