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Before Yin and Yang were distinguished, there was only one undifferentiated, chaotic Qi (vital energy). When Qi combined to form Yin and Yang, clear and turbid qualities emerged. The clear quality floats and rises naturally, while the turbid quality sinks and descends; this is their inherent nature. Rising constitutes Yang, descending constitutes Yin; with Yin and Yang occupying different positions, the Two Modes (Liangyi, referring to Heaven and Earth or the two poles of Yin and Yang) are divided. Between the clear and the turbid lies the Middle Qi (Zhong Qi, central energy governing transformation). The Middle Qi serves as the pivot axis for the ascent and descent of Yin and Yang, which corresponds to the element Earth (Tu). As the pivot moves, the clear Qi rotates to the left, ascending and transforming into Fire (Huo); the turbid Qi rotates to the right, descending and transforming into Water (Shui). Transformation into Fire generates Heat (Re), and transformation into Water generates Cold (Han). When the Qi is halfway up but has not yet fully transformed into Fire, it is named Wood (Mu); the Qi of Wood is warm, and if it continues to ascend, accumulated warmth transforms into Fire. When the Qi is halfway down but has not yet fully transformed into Water, it is named Metal (Jin); the Qi of Metal is cool, and if it continues to descend, accumulated coolness transforms into Water. Water, Fire, Metal, and Wood are called the Four Symbols (Si Xiang). The Four Symbols are essentially the ascent and descent of Yin and Yang, and Yin and Yang are essentially the floating and sinking of the Middle Qi. Separately named, they are called the Four Symbols; collectively speaking, they are merely Yin and Yang. Separately discussed, they are Yin and Yang; collectively discussed, they are merely changes arising from the Middle Qi. The Four Symbols rotate in a cycle, completing one revolution per year. Yang ascends in the first half of the year, and Yin descends in the second half. Half-ascent of Yang corresponds to Spring (Chun), full ascent corresponds to Summer (Xia); half-descent of Yin corresponds to Autumn (Qiu), full descent corresponds to Winter (Dong). Spring generation and Summer growth are the Qi of Wood and Fire, hence Spring is warm and Summer is hot; Autumn harvesting and Winter storing are the Qi of Metal and Water, hence Autumn is cool and Winter is cold. Earth occupies the central position and thrives during the last month of each season (eighteen days each), but its time of command lies within the sixth month. Earth combines with the Four Symbols, which is termed the Five Elements (Wu Xing).

The principle of the Five Elements involves mutual generation (Sheng) and mutual restriction (Ke). Wood generates Fire, Fire generates Earth, Earth generates Metal, Metal generates Water, and Water generates Wood; Wood restricts Earth, Earth restricts Water, Water restricts Fire, Fire restricts Metal, and Metal restricts Wood; their mutual generation and restriction operate through Qi rather than substance (Zhi). Once fixed substances are formed, generation and restriction can no longer occur. Generally, the positions of Heaven and Earth are cold in the North and hot in the South, warm in the East and cool in the West. Yang ascending in the East produces warm Qi forming Spring; ascending in the South produces hot Qi forming Summer; Yin descending in the West produces cool Qi forming Autumn; descending in the North produces cold Qi forming Winter. The warmth of Spring generates the heat of Summer; the heat of Summer generates the coolness of Autumn; the coolness of Autumn generates the cold of Winter; the cold of Winter generates the warmth of Spring. Earth is the mother of the Four Symbols and essentially generates them. The statement "Fire generates Earth" exists because Fire's palace is located after the Fire command of the sixth month, when dampness is abundant; dampness is the Qi of Earth. In reality, the intermingling steaming of Water and Fire generates dampness. During the sixth month, Fire is above Earth and Water is below Earth; cold and heat press against each other, causing dampness to move. Dampness is the Middle Qi between Water and Fire. Earth resides in the Southwest position; the South is hot and the West is cool, hence it is said that "Fire generates Earth, and Earth generates Metal." Mutual restriction refers to controlling excess. The nature of Wood is dispersing; restricting it with Metal Qi prevents excessive dispersion. The nature of Fire is rising and flaming; subduing it with Water Qi prevents excessive flaming. The nature of Earth is moist and sticky; venting it with Wood Qi prevents excessive moisture. The nature of Metal is contracting; warming it with Fire Qi prevents excessive contraction. The nature of Water is descending and moistening; infiltrating it with Earth Qi prevents excessive moisture. These are all the wondrous effects of natural Qi transformation.