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1. The most refined and pure part of the physical form is named the Heart (Xin), which contains innate goodness and original truth (Tianzhen). This single qi of original truth serves as the ancestor of spirit (Shen) and essence (Jing); its substance is Jing, while its function is Shen.
[Note] For both animals and plants, once a form exists, the most refined and pure aspect of that form is termed the Heart. In animals, the heart resembles a hanging lotus, containing the spiritual nature endowed by Heaven—void, luminous, and unobscured. In plants, the "heart" refers to the central bud, containing the life force endowed by Heaven—endlessly generating and thriving. Without this Heart, the form would lack a master, and its innate goodness or vitality would have no foundation. Conversely, without innate goodness or vitality, the Heart would be useless, amounting merely to a lump of dead flesh or a withered plant bud. Although humans are the noblest among animals, they share this innate goodness with all animals, rooted in Original Truth (Tianzhen). The Qi of Original Truth, when analyzed separately, comprises Jing, Qi, and Shen. Thus it is said: "Jing constitutes the substance, while Shen constitutes the function." When viewed collectively, they form a unified Qi; thus it is said: "The single Qi of Original Truth is the source of Spirit and Essence."

2. Shen arises from the wondrous union of Jing and Qi. The Hun (Ethereal Soul), which accompanies Shen, is the spiritual aspect of Yang. The Po (Corporeal Soul), which enters and exits with Jing, is the spiritual aspect of Yin. Yi (Intention) is the mental activity of the Heart that has not yet manifested. When Yi is focused, it is called Zhi (Will). The transformation of Zhi is named Si (Reflection/Thought). Planning for the distant future through Si is called Lv (Deliberation). Wisdom (Zhi) arises from applying Lv to handle affairs.
[Note] Hun is the spirituality of Yang, accompanying Shen in its movements; Po is the spirituality of Yin, entering and exiting together with Jing. Generally, the mechanism of Shen does not depart from Jing and Qi, nor does it mix with them; hence it is described as arising from a "wondrous union." Therefore, regarding Shen, it transcends Jing and Qi; regarding Jing and Qi, Shen resides within them. Yi refers to the mental activity of the Heart that is in motion but not yet manifest. Zhi refers to what Yi focuses upon. Si refers to the dynamic changes of Zhi. Lv refers to using Si to plan for the long term. Zhi (Wisdom) refers to handling matters based on Lv. These are all functions of the transformations of the Conscious Spirit (Shi Shen).