《易》有太极，是生两仪，周子惧人之不明，而制为太极图。无极而太极，无极
者，未分之太极也。太极者，已分之阴阳也。一中分太极，中字之象形，正太极之形
也。一叩伏羲之奇，一而圆之，即是无极，既曰先天太极。天尚未生，尽属无形，何为
伏羲画一奇？周子画一圈，又涉形迹矣。曰∶此不得已，而开示后学之意也。人受天
地之中以生，亦具有太极之形，在人身之中，可不究心乎！
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命门在人身之中，对脐，附脊骨，自上数下，则为十四椎，自下数上则为七椎，
《内经》曰∶七节之旁有小心，此处两肾所寄，左边一肾属阴水，右边一肾属阳水，各
开一寸五分，中间是命门所居之宫，既太极图中之白圈也。其右旁一小白窍，即相火
也。其左旁之小黑窍，即天一之真水也。此一水一火，俱属无形之气，相火禀命于命
门，真水又随相火，自寅至申，行阳二十五度；自酉至丑，行阴二十五度，日夜周流于
五脏六腑之间，滞则病，息则死矣。人生男女，交媾之时，先有火会，而后精聚，故曰
火在水之先。人生先生命门火，此褚齐贤发前人之所未发，世谓父精母血非也。男女俱
以火为先，男女俱有精，但男子阳中有阴，以火为主，女子阴中有阳，以精为主，谓阴
精阳气则可，男女合此，二气交聚，然后成形，成形俱属后天矣。后天百骸俱备，若无
一点先天火气，尽属死灰矣。然元阳君主之所以为应事接物之用者，皆从心上起经纶，
故以心为主。至于栖真养息，而为生生化化之根者，独脏于两肾之中，故尤重于肾，其
实非肾，亦非心也。（李时珍曰∶命门，为藏精系胞之物，其体非脂非肉，白膜裹之，
在脊骨第七节，两肾中央，系着于脊下，通二肾，上通心肺，贯脑，为生命之
原，相火之主，精气之腑，人物皆有之。主人生物皆由此出，男女媾精，皆禀此命火
以结胎，人之穷通寿夭，皆根于此。）
两肾俱属水，左为阴水，右为阳水，以右为命门，非也。命门在两肾中间。
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命门左边小黑圈是真水之穴，命门右边小白圈是相火之穴，此一水一火俱无形，日夜潜行不息。
《易经》中有“太极”的概念，由此生出阴阳两仪。周敦颐担心人们不明白这个道理，所以绘制了太极图。“无极”转化为“太极”，所谓“无极”，就是尚未分化的太极；所谓“太极”，就是已经分化的阴阳。中间的一划分割了太极，“中”字的字形结构，正是太极的形状。一画对应伏羲氏所画的阳爻（奇），将其画成圆形，即是无极，这被称为先天太极。在天尚未生成之前，一切都属于无形状态，为什么伏羲要画这一阳爻呢？周敦颐画了一个圆圈，似乎又落入了有形迹的范畴。回答说：这是出于无奈，为了向后世学者展示心意的做法。人禀受天地之中的气而生，也具备太极的形状，在人体之中，怎能不深入研究呢！
命门位于人身中部，正对肚脐，附着于脊柱骨上。从上往下数，是第十四节椎骨；从下往上数，是第七节椎骨。《黄帝内经》说：“第七节旁边有小心”，这里就是两肾寄居的地方。左边的一肾属阴水，右边的一肾属阳水，两肾各分开一寸五分，中间是命门所在的宫位，也就是太极图中那个白色的圆圈。其右侧旁有一个小白窍，就是相火。其左侧旁有一个小黑窍，就是天一之真水。这一水一火，都属于无形的元气。相火听命于命门，真水跟随相火，从寅时到申时，运行于阳分二十五度；从酉时到丑时，运行于阴分二十五度，日夜在五脏六腑之间循环流动，如果停滞就会生病，如果停止就会死亡。人生育男女，在交媾的时候，先有火的会合，然后精气才聚集，所以说“火在水之先”。人生下来首先拥有的是命门之火，这是褚齐贤阐发了前人未曾发现的问题。世人所说的父精母血是不对的。男女都以火为先导，男女都有精，但男子阳中有阴，以火为主；女子阴中有阳，以精为主。可以说阴中有精、阳中有气，男女结合，二气交汇聚合，然后形成形体，形成的形体都属于后天了。后天的身体百骸虽然具备，如果没有一点先天的火气，就全都是死灰了。然而元阳君主之所以能够用来应对事物、接触万物的作用，都是从心上发起经纶谋划的，所以以心为主导。至于栖息真气、保养气息，作为生生不息的根本，唯独藏在于两肾之中，所以尤其重视肾，但其实既不是肾，也不是心。（李时珍说：命门，是藏精和系胞的器官，它的质地既不是脂肪也不是肌肉，由白膜包裹着，位于脊柱第七节，两肾中央，连接在脊骨下方，贯通两肾，向上通达心肺，贯穿脑部，是生命的本源，相火的主宰，精气的府库，人和动物都有它。主人产生万物都由此出发，男女交媾结胎，都禀受这个命火来形成胎儿，人的穷达通塞、寿命长短，都根源于此。）
The *I Ching* (Book of Changes) contains the concept of *Taiji* (Supreme Ultimate), from which arise the *Liangyi* (Two Modes, i.e., Yin and Yang). Zhou Dunyi, fearing that people would not understand this principle, composed the *Taiji Tu* (Diagram of the Supreme Ultimate). "Wuji" transforms into "Taiji"; what is called "Wuji" (Non-Ultimate) is the Taiji before differentiation; what is called "Taiji" is the Yin and Yang after differentiation. The central stroke divides the Taiji; the pictographic form of the character "Zhong" (Middle/Center) corresponds precisely to the shape of the Taiji. One line corresponds to the Yang Yao (odd line) drawn by Fuxi; drawing it as a circle represents Wuji, which is referred to as the Pre-Heaven Taiji. Before Heaven was generated, everything belonged to the formless state. Why did Fuxi draw this single Yang line? Zhou Dunyi drew a circle, which seems to have fallen into the realm of tangible traces. The answer is: This was done out of necessity to reveal the intent to later scholars. Humans are born receiving the Qi of the Middle from Heaven and Earth, and thus possess the form of Taiji. Within the human body, how can one fail to study it earnestly!
The Mingmen (Gate of Life) is located in the middle of the human body, opposite the navel, attached to the vertebral column. Counting from top to bottom, it is at the fourteenth vertebra; counting from bottom to top, it is at the seventh vertebra. The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "Beside the seventh section lies the 'Xiaoxin' (Small Heart)." This is where the two Kidneys reside. The left Kidney belongs to Yin Water, and the right Kidney belongs to Yang Water. The two Kidneys are separated by one cun and five fen on each side. In the middle lies the palace of the Mingmen, which corresponds to the white circle in the Taiji Tu. To its right is a small white aperture, which is the *Xianghuo* (Ministerial Fire). To its left is a small black aperture, which is the *Zhen Shui* (True Water) of Tian Yi (One from Heaven). This Water and Fire both belong to formless Qi. The Ministerial Fire takes orders from the Mingmen, and the True Water follows the Ministerial Fire. From Yin hour to Shen hour, it circulates twenty-five degrees in the Yang phase; from You hour to Chou hour, it circulates twenty-five degrees in the Yin phase. It flows continuously day and night among the Five Zang and Six Fu organs. If it stagnates, disease occurs; if it ceases, death ensues. When humans procreate, there is first the convergence of Fire, followed by the gathering of Essence. Therefore, it is said that "Fire precedes Water." At birth, one first possesses the Fire of the Mingmen. This insight was revealed by Chu Qixian, uncovering what predecessors had not stated. The worldly view that "the father provides Jing (Essence) and the mother provides Blood" is incorrect. Both men and women prioritize Fire. Both have Jing, but in men, Yang contains Yin, with Fire as the primary aspect; in women, Yin contains Yang, with Jing as the primary aspect. It is correct to say that Yin contains Jing and Yang contains Qi. When male and female energies combine and interact, the physical form is then created. The formed body belongs entirely to Post-Heaven. Although the Post-Heaven body possesses all limbs and bones, without even a spark of Pre-Heaven Fire Qi, it would be nothing but dead ash. However, the function of the Yuan Yang (Original Yang) Monarch in responding to affairs and interacting with things originates from the Heart, which initiates planning and management; thus, the Heart is considered the master. As for dwelling in Truth and nurturing breath, serving as the root of continuous generation and transformation, this resides exclusively within the two Kidneys; therefore, the Kidneys are particularly emphasized. Yet, in reality, it is neither the Kidneys nor the Heart. (Li Shizhen said: The Mingmen is the organ that stores Jing and connects to the Bao (Uterus). Its substance is neither fat nor flesh, but wrapped in a white membrane. Located at the seventh vertebra of the spine, in the center between the two Kidneys, it attaches below the spine, connecting to both Kidneys, ascending to connect with the Heart and Lungs, and penetrating the brain. It is the origin of life, the master of Ministerial Fire, and the residence of Jing and Qi. All humans and animals possess it. All living things originate from here. When men and women conceive, they all rely on this Mingmen Fire to form the fetus. A person's fortune or misfortune, longevity or shortness of life, all stem from this.)
Both Kidneys belong to Water; the left is Yin Water, and the right is Yang Water. To consider the right Kidney as the Mingmen is incorrect. The Mingmen is located between the two Kidneys.
The small black circle to the left of the Mingmen is the aperture of True Water; the small white circle to the right of the Mingmen is the aperture of Ministerial Fire. This Water and Fire are both formless, moving secretly and ceaselessly day and night.