“[When] yin and yang not yet differentiated, the one qi is mixed and indistinct. [Since this] qi contains yin and yang, then it has clear and turbid [portion], the clear then floats and rises, the turbid then sinks and descends, this is their spontaneous nature.
The rising then becomes yang, the descending then becomes yin; yin and yang have separate positions; the two yi divide. [That which resides] in the space between the clear and the turbid, this is called center qi; the center qi is the pivoting axis of the ascent and descent of yin and yang, it is that which is called earth.”－ Huang Yuan Hua- 1705BCE
Well known throughout Daoism, the unamable Dao goes through its multiplicity. Out of nothing, a unity of oneness occurs, Wu ji is formed. Out of Wu ji, the great ultimate, Tai ji arises from. Tai Ji, the great embrace is the union and separation of duality, from the passage above in the Si Xian Xin Yuan, The Four Sage’s Heart initiation, the creation of Yin and Yang becomes very clear. A process of differentiation occurs through the spontaneity of nature, where Yin and Yang become qualified into the Clear and the Turbid. The clear has the quality of rising, and the turbid has the quality of descending. This is of their nature.
The Shou gua describes Yin and Yang before it was called yin and yang, as the way of Shadow and Light, and the way of Soft and Firm. Duality takes it shape in the spontaneous arising nature of phenomena. In between the two, is a pivoting axis of rising and falling where Qi is formed. Qi can be seen as the force between the two, a middle ground of communication between the two extremes. Here there is a Trinity of creation, where the One becomes the Two, and then the Three. We then see out of states of transition four images arising from Yin and Yang. Shao yang, Tai Yang, Shao yin, and Tai yin. These are the four positions of Yin and Yang in its arising and descent.
“[In this] pivoting axis’s movement, the clear qi spins to the left, rising and transforming into fire; turbid qi is revolves to the right, descending and transforming into water, [that which] transforms into fire is then hot, [that which] transforms into water is then cold. Wood’s warm qi rises and does not stop, accumulating warmth becoming hot and transforms becoming fire. Wood’s qi is warm, not fully hot as fire, but as it accumulates it becomes hot and results in fire. Metal’s cool qi descends and does not stop, accumulating cool becoming cold, and transforming into water. Water, fire, metal, wood, these are the names of the four images.”
From this passage we see that Yang at its height is called fire, and Yin in its depth is called water. Fire has the quality of heat, and water has the quality of cold. Growing and arising in between Yin and Yang is Wood, and contracting and condensing in between Yang and Yin is Metal.
The beauty of this explanation is the malleability of understanding. There is a simplicity to the Four “images”. These are natural relatable images that have a strong verisimilitude.
These Four images later on become through explanation and further examination over the centuries as the Four great Animals, The 4 seasons, The five phases, and a prominent part of the I Ching and Chinese Medicine.