凡物之死生，本由阳气。顾今人之病阴虚者十常八九，何谓哉？不知此一阴字，正阳气之根也。
盖阴不可以无阳，非气无以生形也；阳不可以无阴，非形无以载气也。故物之生也生于阳，物之成也成
于阴，此谓元阳元阴，亦曰真精真气也。欲知所以死生者，须察乎阳，察阳者，察其衰与不衰；欲
知所以存亡者，须察乎阴，察阴者，察其坏与不坏，此保生之要法也。
稽之前辈，殊有不识真阴面目，而立言多矫强者。自河间主火之说行，而丹溪以寒苦为补阴，举世宗
之，莫能禁止。揆厥所由，盖以热证明显，人多易见；寒证隐微，人多不知，而且于虚火实火之间，
尤为难辨。亦孰知实热为病者，十中不过三四；虚火为病者，十中常见六七。夫实热者，火之盛，元
气本无所伤，故可以苦寒折之。然当热去即止，不可过用，过用则必伤元气。虚火者，真阴之亏也，真阴
不足，又岂苦劣难堪之物，所能填补？矧沉寒之性，绝无生意，非惟不能补阴，抑且善败真火。第阴性柔
缓，因循玩用，暗损寿元，勿之觉耳。故有老人亦喜凉者，正以元阳本足，故能受寒，非寒凉寿之也。
余请详言真阴之象、真阴之藏、真阴之用，真阴之病。真阴之治，以悉其义。
所谓真阴之象者，阳以阴为根也。经曰∶五脏者，主脏精者也不可伤，伤则失守而阴虚，阴虚则无
气，无气则死矣。非以精为真阴乎？又曰∶形肉已脱，九候虽调犹死。非以形为真阴乎？观形质之坏与不坏
，即真阴之伤与不伤，此
真阴之象，不可不察也。
所谓真阴之藏者，凡五脏五液，各有所主，经曰∶肾者主水，受五脏六腑之精而藏之。故五液皆归乎
精，而五精皆统乎肾。肾有精室，是曰命门，为天一所居，即真阴之腑。精藏于此，精即真阴之水也；气化
于此，气即阴中之火也。命门居两肾之中，而水火具焉，消长系焉，故为受生之初，为性命之本。欲治真
阴而舍命门，非其治也。此真阴之藏，不可不察也。
所谓阴之用者，凡水火之功，不可缺一。命门之火，谓之元气；命门之水，谓之元精。五液充则形
体赖以强壮，五气治则营卫赖以和调。此命门之水火，即十二脏之化源。故十二脏之阴阳，皆赖资之以为治
。此皆真阴之用，不可不察也。
所谓真阴之病者，凡阴气本无有余，阴病皆因不足。即如阴胜于下者，原非阴盛，以命门之火衰也
；阳胜以标者，原非阳盛，以命门之水亏也。水亏则阴虚之病叠出，火衰则阳虚之证迭生，如戴阳者面赤如
朱，格阳者外热如火。或口渴咽焦，引水以自救；或躁扰狂越，欲卧于泥中；或五心烦热而消瘅骨蒸；或二
便秘结而溺浆如汁；或吐血衄血；或咳嗽遗精；或斑黄无汗，由津液之枯涸；或中风螈 ，以精血之败伤。
凡此之类，有属无根之焰，有因火不归原，是皆阴不足以配阳，病在阴中之水也。又如火亏于下，或为神气
之昏沉，或为动履之困倦。其有头目眩晕而七窍偏废者，有咽喉哽咽而呕恶气短者，此皆上焦之阳虚也；有
饮食不化而吞酸反胃者，有痞满隔塞而水泛为痰者，皆中焦之阳虚也；有清浊不分而肠鸣滑泄者，有阳痿精
寒而脐腹多痛者，皆下焦之阳虚也。又或畏寒洒洒者，以火脏之阳虚，不能御寒也；或
肌肉膨胀者，以土脏之阳虚，不能制水也；或拘挛痛痹者，以木脏之阳虚，不能营筋也；或寒嗽虚喘
，身凉自汗者，以金脏之阳虚，不能保肺也；或遗精血泄；二便失禁，腰骨如折，骨痛之极者，以水脏之
阳虚，精髓内竭也。凡此之类，皆阳不足以胜阴，病在阴中之火也。王太仆曰∶寒之不寒，责其无水；
热之不热，责其无火，无水无火，皆在命门。故曰阴虚之病，不可不察也。
所谓真阴之治者，凡乱有所由起，病有所由生，故治病必当求其本。盖五脏之本，本在命门；神气之
本，本在元精，此即真阴之谓也。王太仆曰∶壮水之主，以制阳光；益火之源，以消阴翳。惟薛立斋独得其
妙，而常用仲景八味丸、钱氏六味丸，即益火、壮水之剂也。寒邪中人，本属表症，而汗液之化，必由乎
阴；中风为病，身多偏枯，而筋脉之败，必由乎阴。虚劳生火，非壮水何以救其燎原；泻利亡阴。非补
肾何以因其门户？臌胀由乎水邪，主水须求水脏；关格本乎阴虚。欲强阴舍阴不可。此数者，乃疾病中最大
纲领，明者觉之，可因斯而三反矣。
凡事物的生死，根本在于阳气。然而如今人们患阴虚病的十有八九，这是为什么呢？不知道这个“阴”字，正是阳气的根本。
大概阴不能没有阳，没有气就无法生成形体；阳不能没有阴，没有形体就无法承载气。所以万物的生长源于阳，万物的成熟成于阴，这称为元阳、元阴，也称为真精、真气。想要了解导致生死的原因，必须考察阳气，考察阳气，是看它衰退还是不衰退；想要了解导致存亡的原因，必须考察阴气，考察阴气，是看它败坏还是不败坏，这是保养生命的要点。
考察前代医家，大多不认识真阴的真面目，立论多偏执强硬。自从刘河间主张火说流行后，朱丹溪以寒凉苦味药物作为补阴之法，举世尊崇，无人能禁止。推究其缘由，大概是因为热证表现明显，人们容易看见；寒证隐微，人们往往不知道，而且在虚火与实火之间，尤其难以辨别。又有谁知道，因实热致病的人，十人中不过三四；因虚火致病的人，十人中常见六七。所谓实热，是火的亢盛，元气本来没有受伤，所以可以用苦寒药来折服它。然而应当热去即止，不可过度使用，过度使用必然会损伤元气。所谓虚火，是真阴的亏损，真阴不足，又岂能用那些苦涩难以下咽的药物所能填补？况且沉寒之性的药物，完全没有生机，不仅不能补阴，反而善于败坏真火。只是阴性柔缓，因循苟且地滥用，暗中损害寿命，人们却察觉不到罢了。所以有的老人也喜欢凉性食物，正是因为元阳原本充足，所以能承受寒凉，并不是寒凉之物能使人长寿。
我请求详细阐述真阴的征象、真阴的藏所、真阴的作用、真阴的病证以及真阴的治疗，以便完全明白其中的义理。
所谓真阴的征象，是阳以阴为根本。《内经》说：五脏中主藏精的器官不可以受伤，受伤就会失守而导致阴虚，阴虚就没有气，没有气就会死亡。这不就是把精视为真阴吗？又说：如果形体肌肉已经脱陷，即使九候脉象调和也必死无疑。这不就是把形视为真阴吗？观察形质的败坏与否，就知道真阴是否受伤，这就是真阴的征象，不可不考察。
所谓真阴的藏所，凡是五脏和五液，各有其所主，《内经》说：肾主水，接受五脏六腑的精气而贮藏起来。所以五液都归于精，五精都由肾统摄。肾中有精室，称为命门，是天一之气居住的地方，也就是真阴之腑。精藏于此，精就是真阴之水；气化于此，气就是阴中之火。命门位于两肾之中，水火皆具备，消长关系系于此，所以它是受生的初始，是性命的根本。想要治疗真阴却舍弃命门，不是正确的治疗方法。这就是真阴的藏所，不可不考察。
所谓阴的作用，凡是水火的功能，缺一不可。命门之火，称为元气；命门之水，称为元精。五液充盈则形体依靠它而强壮，五气调治则营卫依靠它而和谐。这命门的水火，就是十二脏腑的气化源头。所以十二脏腑的阴阳，都依赖它来维持治疗。这些都是真阴的作用，不可不考察。
所谓真阴的病证，凡是阴气本来就不会有余，阴病都是因为不足。就像阴胜于下者，原本不是阴盛，而是因为命门之火衰微；阳胜在标者，原本不是阳盛，而是因为命门之水亏虚。水亏则阴虚的病证接连出现，火衰则阳虚的证候迭次发生，如戴阳证见面赤如朱砂，格阳证见外热如火。或者口渴咽干焦灼，引水来自救；或者烦躁扰乱狂越，想卧在泥水中；或者五心烦热并伴有消瘦骨蒸；或者二便秘结且小便如汁；或者吐血衄血；或者咳嗽遗精；或者发斑发黄无汗，这是由于津液枯涸；或者中风抽搐，这是由于精血败伤。
像这些情况，有的是属于无根之火，有的是因为火不归原，这都是阴不足以配阳，病在阴中之水。另外如果火亏于下，或者表现为神气昏沉，或者表现为行动困倦。有的出现头目眩晕且七窍功能偏废丧失，有的出现咽喉哽咽且呕吐恶心气短，这些都是上焦的阳虚；有的出现饮食不化且吞酸反胃，有的出现痞满隔塞且水泛为痰，这些都是中焦的阳虚；有的出现清浊不分且肠鸣滑泄，有的出现阳痿精冷且脐腹多痛，这些都是下焦的阳虚。又或者畏寒战栗，是因为火脏（心）的阳虚，不能抵御寒冷；或者肌肉肿胀，是因为土脏（脾）的阳虚，不能制约水湿；或者拘挛疼痛痹阻，是因为木脏（肝）的阳虚，不能濡养筋脉；或者寒嗽虚喘，身凉自汗，是因为金脏（肺）的阳虚，不能保肺；或者遗精血泄，二便失禁，腰骨如折断，骨痛至极，是因为水脏（肾）的阳虚，精髓内竭。像这些情况，都是阳不足以胜阴，病在阴中之火。王太仆说：用寒药治寒而不退，要责之于无水；用热药治热而不退，要责之于无火，无水无火，都在命门。所以说阴虚的病，不可不考察。
所谓真阴的治疗，凡是紊乱有所由起，病有所由生，所以治病必须探求根本。大概五脏的根本，在于命门；神气的根本，在于元精，这就是真阴的含义。王太仆说：壮水之主，以制阳光；益火之源，以消阴翳。只有薛立斋独得其妙，而常用张仲景的八味丸、钱乙的六味丸，这就是益火、壮水的方剂。寒邪侵入人体，本属表症，但汗液的化生，必然由阴提供基础；中风致病，身体多偏枯，但筋脉的败坏，必然由阴提供基础。虚劳生火，不用壮水的方法怎能扑灭燎原之火；泻利亡阴，不补肾怎么能守住门户？鼓胀由于水邪，主治水须求之于水脏；关格本乎阴虚，想要强阴舍阴是不可能的。这几条，是疾病中最大的纲领，明眼人觉察到这一点，可以由此反复推演了。
The life and death of all things fundamentally depend on Yang Qi. However, nowadays nine out of ten people suffer from Yin deficiency. Why is this? It is because one does not realize that this "Yin" is precisely the root of Yang Qi.
Generally speaking, Yin cannot exist without Yang; without Qi, there can be no generation of Form. Yang cannot exist without Yin; without Form, there can be no bearing of Qi. Therefore, the growth of things arises from Yang, while their maturation is accomplished by Yin. This is referred to as Original Yang and Original Yin, also known as True Essence (Zhen Jing) and True Qi (Zhen Qi). To understand the causes of life and death, one must examine Yang; examining Yang involves observing whether it is declining or not. To understand the causes of survival and demise, one must examine Yin; examining Yin involves observing whether it is deteriorating or not. This is the essential method for preserving life.
Reviewing the works of predecessors, many failed to recognize the true nature of True Yin, leading to rigid and dogmatic theories. Since Liu Hejian's theory emphasizing Fire became prevalent, Zhu Danxi advocated using bitter-cold herbs to tonify Yin, a view universally adopted and unchallenged. The reason for this lies in the fact that Heat syndromes are obvious and easily observed, whereas Cold syndromes are subtle and often overlooked. Furthermore, distinguishing between Deficient Fire and Excess Heat is particularly difficult. Few realize that among cases caused by Excess Heat, only three or four out of ten occur, whereas those caused by Deficient Fire are common, occurring six or seven times out of ten. Excess Heat represents the flourishing of Fire, where Original Qi is initially uninjured; thus, it can be subdued with bitter-cold herbs. However, treatment should cease once the Heat is resolved; overuse will inevitably damage Original Qi. Deficient Fire, on the other hand, results from the depletion of True Yin. When True Yin is insufficient, how can harsh, bitter, and cold substances possibly replenish it? Moreover, the nature of deeply cold herbs lacks vitality; they not only fail to tonify Yin but also tend to destroy True Fire. Due to the gentle and lingering nature of Yin pathology, improper use secretly damages longevity without being perceived. Thus, some elderly individuals who prefer coolness do so because their Original Yang is sufficient to withstand cold; it is not that coolness extends life.
I request to elaborate in detail on the manifestations, residence, functions, pathologies, and treatments of True Yin, to fully elucidate its principles.
Regarding the manifestations of True Yin: Yang takes Yin as its root. The *Classic of Internal Medicine* states: "The Zang organs that store Essence must not be injured; injury leads to loss of control and Yin deficiency, Yin deficiency leads to lack of Qi, and lack of Qi leads to death." Does this not designate Essence as True Yin? It also states: "If flesh and form have wasted away, even if the nine pulse positions are harmonious, death will ensue." Does this not designate Form as True Yin? Observing whether physical structure is intact or deteriorated reveals whether True Yin is injured or not. These are the manifestations of True Yin, which must be examined.
Regarding the residence of True Yin: Each of the five Zang organs and five fluids has its specific governance. The *Classic of Internal Medicine* states: "The Kidney governs Water and receives the Essence of the five Zang and six Fu organs to store it." Thus, the five fluids return to Essence, and the five Essences are unified by the Kidney. Within the Kidney lies the chamber of Essence, called the Gate of Life (Ming Men), which is the dwelling place of Heavenly One, i.e., the Fu organ of True Yin. Essence is stored here; Essence is the Water of True Yin. Qi transformation occurs here; Qi is the Fire within Yin. The Gate of Life resides between the two Kidneys, possessing both Water and Fire, governing their waxing and waning. Hence, it is the beginning of conception and the root of life and destiny. Treating True Yin while neglecting the Gate of Life is incorrect. This is the residence of True Yin, which must be examined.
Regarding the function of Yin: The functions of Water and Fire are indispensable. The Fire of the Gate of Life is called Original Qi; the Water of the Gate of Life is called Original Essence. When the five fluids are abundant, the body relies on them for strength; when the five Qi are regulated, Ying and Wei (Defensive and Nutritive Qi) rely on them for harmony. The Water and Fire of the Gate of Life are the source of transformation for the twelve Zang-Fu organs. Therefore, the Yin and Yang of the twelve organs all depend on it for regulation. These are the functions of True Yin, which must be examined.
Regarding the pathology of True Yin: Yin Qi is never in excess; Yin diseases always arise from insufficiency. For instance, what appears as Yin dominance in the lower jiao is originally not Yin excess, but rather the decline of Fire in the Gate of Life. What appears as Yang dominance at the surface is originally not Yang excess, but rather the depletion of Water in the Gate of Life. Depletion of Water leads to successive Yin deficiency diseases; decline of Fire leads to recurring Yang deficiency syndromes. Examples include Dai Yang syndrome (face red like cinnabar) and Ge Yang syndrome (external heat like fire). Symptoms may include thirst and dry throat seeking water for relief; restlessness, agitation, and mania desiring to lie in mud; five-palm heat accompanied by emaciation and bone-steaming fever; constipation of both bowels and urine resembling juice; hematemesis and epistaxis; coughing and spermatorrhea; macules, jaundice, and anhidrosis due to exhaustion of body fluids; or wind-stroke with convulsions due to damage to essence and blood.
Such conditions belong either to rootless flames or to Fire failing to return to its origin. All result from Yin being insufficient to balance Yang, indicating disease in the Water of Yin. Conversely, if Fire is deficient in the lower jiao, it may manifest as mental dullness or physical fatigue. Dizziness and visual/auditory impairment indicate upper jiao Yang deficiency. Throat obstruction, nausea, and shortness of breath indicate upper jiao Yang deficiency. Indigestion, acid regurgitation, and vomiting indicate middle jiao Yang deficiency. Fullness, blockage, and phlegm from water flooding indicate middle jiao Yang deficiency. Mixing of clear and turbid, intestinal murmurs, and diarrhea indicate lower jiao Yang deficiency. Impotence, cold sperm, and abdominal pain indicate lower jiao Yang deficiency. Aversion to cold and shivering indicate Yang deficiency of the Fire Zang (Heart), unable to resist cold. Muscle distension indicates Yang deficiency of the Earth Zang (Spleen), unable to control water. Spasms and painful bi-syndromes indicate Yang deficiency of the Wood Zang (Liver), unable to nourish sinews. Cold cough, deficiency asthma, cool body, and spontaneous sweating indicate Yang deficiency of the Metal Zang (Lung), unable to protect the Lung. Spermatorrhea, bloody stool, incontinence, broken-back sensation, and extreme bone pain indicate Yang deficiency of the Water Zang (Kidney), with internal exhaustion of essence and marrow. Such conditions result from Yang being insufficient to overcome Yin, indicating disease in the Fire of Yin. Wang Taipu stated: "When cold fails to treat cold, blame the lack of Water; when heat fails to treat heat, blame the lack of Fire. Both lack of Water and Fire reside in the Gate of Life." Therefore, Yin deficiency diseases must be examined.
Regarding the treatment of True Yin: Since disorders have origins and diseases have causes, treating disease requires seeking the root. The root of the five Zang organs lies in the Gate of Life; the root of Spirit and Qi lies in Original Essence. This is True Yin. Wang Taipu stated: "Strengthen the master of Water to control the glare of Sunlight; benefit the source of Fire to dissipate the shadows of Yin." Only Xue Lizhai mastered this subtlety, frequently using Zhang Zhongjing's Ba Wei Wan (Eight-Ingredient Pill) and Qian Yi's Liu Wei Wan (Six-Ingredient Pill), which are formulas for benefiting Fire and strengthening Water. When cold pathogens invade, although presenting as exterior syndromes, the transformation of sweat depends on Yin. In wind-stroke, where hemiplegia is common, the deterioration of sinews and vessels depends on Yin. In deficiency consumption generating fire, how else can one extinguish the prairie fire but by strengthening Water? In dysentery causing Yin loss, how else can one secure the gates but by tonifying the Kidney? In distension caused by water pathogens, one must seek the Water Zang to govern water; in Guan Ge syndrome rooted in Yin deficiency, one cannot strengthen Yin by abandoning Yin. These few points are the major guidelines in disease management. Those with insight can reflect upon them repeatedly.