Alchemy
The alchemical discourse of the Cantong qi revolves around Lead and Mercury. Its basic principles proceed directly from its views on the relation between the Dao and the "ten thousand things" (i.e., multiplicity and change). As in the whole of Taoism, this relation is explained by means of a sequence of stages. The absolute principle (Dao) establishes itself as Unity (Yi 一), which divides itself into the active and the passive principles—namely, Qian and Kun, respectively equivalent to original Yang and Yin, or True Yang and True Yin. The re-conjunction of these principles gives birth to all entities and phenomena in the world. All these "stages" occur simultaneously.
The alchemical process consists in tracing the stages of this process in a reverse sequence, in order to recover the hidden One Breath and return to it. In alchemical language, True Lead (☰) and True Mercury (☷) respectively represent True Yang and True Yin. The Yin and Yang entities that respectively contain these authentic principles are represented by "black lead" (i.e., native lead ☵) and cinnabar (☲). In the strict sense of the term, alchemy consists in extracting True Lead from "black lead" and True Mercury from cinnabar, and in joining them to one another.
When the five agents (wuxing) are used to represent the alchemical process, the basic configuration is the same. "Black lead" and cinnabar are Water and Fire, and True Lead and True Mercury are Metal and Wood. In the alchemical process, where the "generation sequence" of the agents is inverted, Water ("black lead") generates Metal (True Lead), and Fire (cinnabar) generates Wood (True Mercury).
Soil, the fifth agent, allows the entire alchemical process to unfold, and also represent its completion. Positioned at the center of the other agents, it is emblematic of Unity containing True Yin and True Yang. Being found within both ingredients of the Elixir, Soil stands for their fundamental unity, and enables them to conjoin.
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