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。一即伏羲之奇，一而图之即是无极。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，可不究心哉。
\r太极图\p04-a41a43.bmp\r
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，两肾在人身中，合成一太极。
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。
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，即太极图中之
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，此褚斋贤发前人之所未发，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，独藏于两肾
之中，故尤重于肾，其实非肾，亦非心也。（《冯氏》）
\r阳水阴水相火真水命门图\p04-a41a44.bmp\r
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，精气之府，人物皆有之，生人生物，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。
《易经》中有太极，由此生出两仪。周敦颐担心人们不明白其中的道理，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，正是太极的形状。这一划即伏羲氏所画的阳爻（奇），用这一划来图示，就代表了无极。既然说是先天太极，此时天尚未生成，一切都属于无形状态，为什么伏羲要画一阳爻，周子要画一圈，这又涉及到了有形迹了呢？回答说：这是不得已而向后来学者开示心意的做法。人禀受天地之中气而生，体内也具有太极的形状，在人体之中，怎能不深入研究呢？
两肾都属于水，左侧为阴水，右侧为阳水，这种说法是不对的。命门位于两肾之间，两肾在人体中，共同合成一个太极。命门左边的小黑圈，是真水的穴位；命门右边的小白圈，是相火的穴位。这一水一火都属无形，日夜潜行不息。
命门位于人体之中，正对肚脐，附着于脊骨之上。从上往下数则是第十四椎，从下往上数则是第七椎。《黄帝内经》说：“第七节旁边有小心。”此处是两肾寄居的地方，左边的肾属于阴水，右边的肾属于阳水，各向外开一寸五分，中间是命门居住的宫室，也就是太极图中的白圈。其右侧旁有一个小白窍，即是相火。其左侧旁有一个小黑窍，即是天一之真水。这一水一火都属于无形的元气，相火受命门的命令支配，真水跟随相火，从寅时到申时，运行阳二十五度，从酉时到丑时，运行阴二十五度，日夜在五脏六腑之间循环流动，停滞则生病，停止则死亡。人在男女交媾之时，先有火会合而后精聚拢，所以说火在水之先。人生下来首先拥有的是命门之火，这是褚斋贤阐发了前人未曾发现的问题。世人认为父精母血的说法是不对的。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。可以说阴精阳气，男女结合此气交聚，然后形成形体，形成的形体都属于后天了。后天百骸俱备，如果没有一点先天的火气，就全是死灰了。然而元阳君主之所以能够应对事物，都是从心上发起经纶谋划的，所以以心为主。至于栖守真性、涵养气息，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，其实既不是肾，也不是心。（出自《冯氏》）
李时珍说：命门是藏精和系胞的物质，它的体状非脂非肉，由白膜包裹着，位于脊骨第七节两肾中央，连接于脊骨，向下连通两肾，向上连通心肺，贯穿脑部，是生命的本源，相火的主宰，精气所在的府库，人和动物都有它，生育人类和生物，都由此而出。男女交媾结精，都禀受此命火来结成胎元，人的穷困显达、长寿短命，都根源于此。
The *I Ching* (Book of Changes) contains the Supreme Ultimate (Taiji), from which the Two Modes (Liangyi, Yin and Yang) are generated. Zhou Dunyi, fearing that people would not understand this principle, created the Diagram of the Supreme Ultimate. "Non-ultimate" transforms into "Supreme Ultimate." What is called "Non-ultimate" is the Supreme Ultimate before differentiation; what is called "Supreme Ultimate" is Yin and Yang after differentiation. The central line divides the Supreme Ultimate; the character shape of "Zhong" (Middle/Center) corresponds exactly to the form of the Supreme Ultimate. This single line represents the Yang Yao (odd line) drawn by Fuxi; diagramming it with this single line represents the Non-ultimate. Since it is referred to as the Pre-heaven Supreme Ultimate, where Heaven has not yet been born and everything belongs to the formless state, why did Fuxi draw a single Yang Yao and Zhou Dunyi draw a circle, thus involving tangible traces? The answer is: this is an不得已 (unavoidable/necessary) method to reveal the intent to later learners. Humans are born receiving the Qi of the Middle from Heaven and Earth, and thus possess the form of the Supreme Ultimate within their bodies. In the human body, how can one fail to study it carefully?
Both kidneys belong to Water. The left is Yin Water, and the right is Yang Water; this view is incorrect. the Mingmen (Gate of Life) is located between the two kidneys. The two kidneys together in the human body constitute one Supreme Ultimate. The small black circle on the left side of the Mingmen is the acupoint of True Water; the small white circle on the right side of the Mingmen is the acupoint of Minister Fire (Xianghuo). This Water and this Fire are both formless, operating secretly and ceaselessly day and night.
The Mingmen is located in the human body, opposite the navel, attached to the spinal column. Counting from top to bottom, it is the fourteenth vertebra; counting from bottom to top, it is the seventh vertebra. The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "Beside the seventh section lies the Small Heart." This place is where the two kidneys reside. The left kidney belongs to Yin Water, and the right kidney belongs to Yang Water. Each extends one cun and five fen outward. In the middle is the palace where the Mingmen resides, which is the white circle in the Diagram of the Supreme Ultimate. The small white orifice on its right is the Minister Fire. The small black orifice on its left is the True Water of Tianyi (One from Heaven). This Water and this Fire both belong to formless Yuan Qi (Original Qi). The Minister Fire receives orders from the Mingmen, and the True Water follows the Minister Fire. From Yin hour to Shen hour, it circulates twenty-five degrees of Yang; from You hour to Chou hour, it circulates twenty-five degrees of Yin. It flows continuously day and night among the Five Zang and Six Fu organs. Stagnation leads to disease, and cessation leads to death. At the time of sexual intercourse between man and woman, the Fire meets first, and then the Essence gathers. Therefore, it is said that Fire precedes Water. Upon birth, humans first possess the Fire of the Mingmen. This insight was expounded by Chu Zhaixian, revealing what predecessors had not yet discovered. The worldly belief that "father provides Jing (Essence) and mother provides Xue (Blood)" is incorrect. Both men and women prioritize Fire as the precursor. Both have Jing, but in men, Yang contains Yin, so Fire is primary; in women, Yin contains Yang, so Jing is primary. It is acceptable to speak of Yin Jing and Yang Qi. When male and female energies intersect and gather, the physical form is then created. The created form belongs to Post-heaven. Although the post-heaven body possesses all bones and limbs, without even a spark of pre-heaven Fire Qi, it would be nothing but dead ash. However, the reason why the Monarch of Yuan Yang can respond to affairs and interact with things is that all planning originates from the Heart (Zang organ); therefore, the Heart is considered primary. As for dwelling in truth and nurturing breath, serving as the root of endless generation and transformation, this is uniquely stored within the two kidneys; thus, the Kidneys are particularly emphasized. In reality, however, it is neither the Kidneys nor the Heart. (From *Feng Shi*)
Li Shizhen stated: The Mingmen is the substance that stores Jing and connects to the Bao (uterus/womb). Its structure is neither fat nor flesh, wrapped in a white membrane. It is located in the center of the two kidneys at the seventh vertebra of the spine, connected to the spine, communicating downward with the two kidneys, upward with the Heart and Lungs, and penetrating the brain. It is the origin of life, the master of Minister Fire, and the mansion of Jing and Qi. All humans and animals possess it. Human reproduction and the creation of all living beings originate from here. When men and women engage in sexual union to combine essence, they all rely on this Mingmen Fire to form the fetus. A person's fortune or misfortune, longevity or shortness of life, all root in this.