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[Figure of the Generation and Completion Numbers of the Five Elements]
This is the numerical system of the Hetu (River Map). The "Wu Shao" (Five Minor/Yang Heavenly Stems) correspond to generation numbers, while the "Wu Tai" (Five Major/Yin Heavenly Stems) correspond to completion numbers. Earth typically utilizes the generation number; therefore, the number ten is not explicitly mentioned, as explained previously.

[Figure of the Five Elements]
Wood, Fire, Earth, Metal, Water: mutual generation is termed "Shun" (Forward/Clockwise). Wood, Earth, Water, Fire, Metal: mutual restriction is termed "Ni" (Reverse/Counter-clockwise).

[Figure of the Five Elements Associated with Heavenly Stems and Earthly Branches]
Jia, Yi, Yin, Mao in the East belong to Wood; Bing, Ding, Si, Wu in the South belong to Fire; Geng, Xin, Shen, You in the West belong to Metal; Ren, Gui, Hai, Zi in the North belong to Water; Chen, Xu, Chou, Wei belong to the four seasons' end months; Wu, Ji are in the Center and all belong to Earth.

[Figure of the Na Yin (Melodic Nature) of the Sixty Jiazi]
The principles of the Five Elements originate from nature. Heaven and Earth's generation involves numbers without exception. The Sages observed the Hetu and deduced these numbers. The sequence states: Heaven One generates Water, Earth Six completes it; Earth Two generates Fire, Heaven Seven completes it; Heaven Three generates Wood, Earth Eight completes it; Earth Four generates Metal, Heaven Nine completes it; Heaven Five generates Earth, Earth Ten completes it. Each of the Five Elements possesses form and substance, but only Water and Fire are the lightest and clearest, representing the beginning of creation. Thus, Heaven uses one odd number to generate Water, and Earth uses two even numbers to generate Fire. From a physical perspective, Water and Fire must come first. By observing the small to understand the large, and the present to verify the past, this can be known. For instance, before plants bear fruit or embryos are conceived, everything originates from Water before taking shape. Thus, Water is the precursor to all things, hence its number is One. Once the signs of transformation appear, Yin and Yang must be distinguished. Since there is Heaven One's Yang Water, there must be Earth Two's Yin Fire; thus, Fire follows second, with the number Two. Once Yin and Yang combine, there must be emergence. Water Qi generates Wood, so Wood follows next, with the number Three. Once there is emergence, there must be harvesting and肃杀 (severing/cold). Dry Qi generates Metal, so Metal follows next, with the number Four. Regarding Heaven Five generating Earth and Earth Ten completing it, it seems Earth is generated last. However, Dai Tinghuai stated: Where there is ground, there is Earth. If Earth were generated last, what would Heaven Three's Wood and Earth Four's Metal attach to? Moreover, Water, Fire, Wood, and Metal all rely on Earth; how could Earth be the last to be born? The reason Earth is associated with Five and Ten is that Five is the center of the complete numbers, and Ten is the extreme of the completion numbers. "Center" implies Earth is unbiased and governs the four directions; "Extreme" implies the destination of all things and the containment of all existence. Neither implies being last. Combining this with the principles of direction and Yin-Yang yields the same result. Water prospers at Zi (Rat), which is the beginning of Yang birth; One is the number where Yang begins, hence Water is One. Fire prospers at Wu (Horse), which is the beginning of Yin birth; Two is the number where Yin begins, hence Fire is Two. Wood prospers in the East; East is Yang, and Three is an odd number also belonging to Yang, hence Wood is Three. Metal prospers in the West; West is Yin, and Four is an even number also belonging to Yin, hence Metal is Four. Earth prospers in the Central Palace and governs the four corners; Five is the middle of the numbers, hence Earth is Five. This is the root of the generation numbers of the Five Elements. Generation numbers precede completion numbers, forming the way of Yin-Yang generation, which is the natural principle of Heaven and Earth. Although the Hetu lists the order of the Five Elements, it essentially distinguishes their Yin and Yang. Once Yin and Yang have an order, the Qi and numbers must have prosperity and decline. As stated in the *Su Wen: Liuyuan Zhengji Dalun* regarding Cold Transformation One, Cold Transformation Six, Disaster Palace One, Disaster Palace Three, etc., all are determined by these numbers. Qibo said: In years of excess, the number corresponds to completion; in years of deficiency, the number corresponds to generation; Earth always uses the generation number. This means that in the five Tai (Major/Yang) years of Jia, Bing, Wu, Geng, Ren, which are excessive, the number corresponds to completion; in the five Shao (Minor/Yin) years of Yi, Ding, Ji, Xin, Gui, which are deficient, the number corresponds to generation. Only Earth commonly uses the generation number because Five is the middle of the numbers, Earth occupies the central position, and encompasses the Qi of the four directions; thus, Earth's number often corresponds to the middle. Although the *Yijing Xici* mentions Heaven Ten completing, the *Su Wen: Sanbu Jiuhou Lun* states: The numbers of Heaven and Earth begin with One and end with Nine. This is why Earth does not wait for Ten to complete. The ancient sages observed the generation and completion numbers to seek Yunqi (Luck and Qi), intending to use numbers to predict the prosperity and decline of Qi transformation, and to show people the methods of imitating Yin and Yang, harmonizing numerology, anticipating annual Qi, and conforming to Heavenly Harmony. This concerns the Way of Life significantly; readers should not neglect it.