七十五难曰∶经言东方实，西方虚，泻南方，补北方，何谓也？然∶金木水火土，当更相平。
东方木也，西方金也。木欲实，金当平之；火欲实，水当平之；土欲实，木当平之；金欲实，火
当平之；水欲实，土当平之。东方者肝也，则知肝实；西方者肺也，则知肺虚。泻南方火，补北
方水。南方火，火者，木之子也；北方水，水者，木之母也。水胜火，子能令母实，母能令子虚，
故泻火补水，欲令金不得平木也。经曰∶不能治其虚，何问其余？此之谓也。余每读至此，未尝
不叹夫越人之得经旨也，而悼夫后人之失经旨也。
先哲有言，凡读书不可先看注解，且将经文反复而详味之，待自家有新意，却以注解参校，
庶乎经意昭然，而不为他说所蔽。若先看注解，则被其说横吾胸中，自家竟无新意矣。余平生佩
服此训，所益甚多。且如《难经》此篇，其言周备纯正，足以为万世法。后人纷纷之论，其可凭乎？
夫实则泻之，虚则补之，此常道也；实则泻其子，虚则补其母，亦常道也。人皆知之。今肝
实肺虚，乃不泻肺而泻心，此则人亦知之。至不补肺补脾，而补肾，此则人不能知，惟越人知之
耳。夫子能令母实，母能令子虚，以常情观之，则曰∶心火实，致肝木亦实，此子能令母实也；
脾土虚，致肺金亦虚，此母能令子虚也。心火实，固由自旺；脾土虚，乃由肝木制之。法当泻心
补脾，则肝肺皆平矣。越人则不然。其子能令母实，子谓火，母谓木，固与常情无异；其母能令
子虚，母谓水，子谓木，则与常情不同矣。故曰∶水者，木之母也。子能令母实一句，言病因也；
母能令子虚一句，言治法也。其意盖曰∶火为木之子，子助其母，使之过分而为病矣。今将何以
处之？惟有补水泻火之治而已。
夫补水者何谓也？盖水为木之母，若补水之虚，使力可胜火，火势退而木势亦退。此则母能虚子之义，所
谓不治之治也。（此虚字与精气夺则虚之不同，彼虚谓耗其真而致虚，此虚谓抑其过而致虚之也。）
若曰不然，则母能令子虚一句，将归之于脾肺乎？既归于脾肺，今何不补脾乎？夫五行之道，其
所畏者畏所克耳。今火太旺，水太亏，火何畏乎？惟其无畏，故愈旺而莫能制。苟非滋水以求胜
之，孰能胜之？水胜火三字，此越人寓意处，当细观之，勿轻忽也。虽泻火补水并言，然其要又
在于补水耳。后人乃曰∶独泻火而不用补水。又曰∶泻火则是补水。得不大违越人与经之意乎？
若果不用补水，经必不言补北方，越人必不言补水矣。虽然，水不虚，而火独暴旺者，固不必补
水亦可也。若先因水虚而致火旺者，不补水可乎？水虚火旺而不补水，则药至而暂息，药过而复
作，将积年累月无有穷已，安能绝其根哉？虽苦寒之药，通为抑阳扶阴，不过泻火邪而已，终非
肾脏本药，不能以滋养北方之真阴也。欲益其阴，非地黄、黄柏之属不可也。且夫肝之实也，其
因有二∶心助肝，肝实之一因也；肺不能制肝，肝实之二因也。肺之虚也，其因亦有二∶心克肺，
肺虚之一因也；脾受肝克，而不能生肺，肺虚之二因也。今补水而泻火，火退则木气削，又金不
受克而制木，东方不实矣。金气得平，又土不受克而生金，西方不虚矣。若以虚则补母言之，肺
虚则当补脾，岂知肝势正盛，克土之深，虽曰补脾，安能敌其正盛之势哉？纵使土能生金，金受
火克，亦所得不偿所失。此所以不补土而补水也。
或疑木旺补水，恐水生木而木愈旺，故闻独泻火不补水之论，欣然而从之。殊不知木已旺矣，
何待生乎？况水之虚，虽峻补尚不能复其本气，安有余力生木哉？若能生木，则能胜火矣。或又
谓∶补水者，欲其不食于母也，不食于母，则金气还矣。岂知火克金，土不能生金，金之虚已极，
尚不能自给，水虽欲食之，何所给乎？若如此，则金虚不由于火之克。土之不生而由于水之食耳，
岂理也哉？纵水不食金，金亦未必能复常也。金不得平木一句，多一不字。所以泻火补水者，正
欲使余得平木也，不字当删去。不能治其虚，何问其余？虚指肺
虚而言也，泻火补水，使金得平木，正所谓能治其虚。不补土，不补金，乃泻火补水，使金自平，
此法之巧而妙者。苟不能晓此法，而不能治此虚，则不须问其他，必是无能之人矣。故曰∶不能
治其虚，何问其余？若夫上文所谓金木水火土更相平之义，不劳解而自明，兹故弗具也。夫越人，
亚圣也，论至于此，敢不敛衽？但恨说者之 蚀之，故辨。
《难经》第七十五难说：经文讲“东方实，西方虚，泻南方，补北方”，这是什么意思呢？回答说：金、木、水、火、土五行，应当互相平衡。
东方属木，西方属金。木气想要充实，金气应当制约它；火气想要充实，水气应当制约它；土气想要充实，木气应当制约它；金气想要充实，火气应当制约它；水气想要充实，土气应当制约它。东方对应肝脏，所以知道是肝气实证；西方对应肺脏，所以知道是肺气虚证。治疗应当泻南方之火，补北方之水。南方属火，火是木的子行；北方属水，水是木的母行。水能胜火，子行能使母行充实，母行能使子行虚弱，所以通过泻火补水，目的是让金气不再去平抑木气（即解除金对木的过度克制）。经文说：“不能治疗其虚证，还问其他什么呢？”说的就是这个道理。我每次读到此处，未曾不感叹越人（秦越人）能够领会经旨，而哀叹后人失去了经旨。
先哲有句话说，凡是读书不可以先看注解，且将经文反复诵读并细细品味，等到自己有了新的心得，再用注解来参校对照，这样经文的意思自然显明，而不被他人的学说所蒙蔽。如果先看注解，就会被对方的学说横亘在心中，自己终究不会有新的见解。我平生佩服这一教诲，受益良多。况且像《难经》这篇，它的言论周全完备、纯正，足以成为万世的法则。后人纷纷议论的那些观点，可以信赖吗？
一般来说，“实证用泻法，虚证用补法”，这是常规之道；“实证泻其子行，虚证补其母行”，这也是常规之道。人们都知道这一点。现在肝实肺虚，却不泻肺而泻心，这也是人们知道的。至于不补肺补脾，反而补肾，这就不是普通人能知道的，只有越人知道罢了。所谓“子能令母实，母能令子虚”，从常理来看，会说：心火实证，导致肝木也实，这是子能令母实；脾土虚证，导致肺金也虚，这是母能令子虚。心火实，固然由于自身旺盛；脾土虚，是由于肝木克制它所致。治法应当泻心补脾，那么肝和肺就都平衡了。越人却不是这样。他说“子能令母实”，子指火，母指木，这确实与常理无异；但他所说的“母能令子虚”，母指水，子指木，这就与常理不同了。所以说：水是木的母行。“子能令母实”这一句，讲的是病因；“母能令子虚”这一句，讲的是治法。他的意思是：火是木的子行，子行助长母行，使其过分而为病。现在将如何处理呢？只有采用补水泻火的治法罢了。
什么叫补水呢？因为水是木的母行，如果补充水的不足，使水的力量能够胜过火，火势退却，木势也随之退却。这就是“母能令子虚”的含义，也就是所谓的“不治之治”。（这里的“虚”字与《内经》中“精气夺则虚”的虚不同，彼处的虚是指耗损真阴而导致虚损，此处的虚是指抑制过亢而导致虚弱。）如果说不是这样，那么“母能令子虚”这一句，难道要归结到脾肺吗？既然归结到脾肺，现在为什么不补脾呢？五行的规律，它所畏惧的是被其所克制的对象。现在火太旺，水太亏，火还畏惧什么？正因为无所畏惧，所以更加旺盛而无法制约。如果不是滋水以求战胜它，谁能战胜它？“水胜火”这三个字，是越人寓意的关键之处，应当仔细观察，不可轻视。虽然文中同时提到泻火和补水，但重点又在于补水罢了。后人却说：只泻火而不补水。又说：泻火就是补水。这难道不是大大违背了越人和经文的原意吗？如果果然不用补水，经文必定不会说“补北方”，越人也必定不会说“补水”了。虽然如此，如果水不虚，而火单独暴旺，那固然是不必补水也可以的。如果是先因水虚而导致火旺，不补水可以吗？水虚火旺而不补水，那么药物到达时暂时平息，药力过后又会复发，这将积年累月没有穷尽，怎么能断绝病根呢？即使是苦寒的药物，通常都是抑制阳热扶持阴液，不过只是泻火邪而已，终究不是肾脏的本药，不能滋养北方的真阴。想要益阴，非地黄、黄柏这类药物不可。
况且肝实的成因有二：一是心火助长肝木，这是肝实的一个原因；二是肺金不能制约肝木，这是肝实的第二个原因。肺虚的成因也有二：一是心火克制肺金，这是肺虚的一个原因；二是脾土受肝木克制，而不能生养肺金，这是肺虚的第二个原因。现在通过补水而泻火，火退则木气削弱，另外金气不受火克而能制约木气，东方（肝）就不实了。金气得平，土气也不受木克而生金，西方（肺）就不虚了。如果按照“虚则补其母”来说，肺虚则应当补脾，怎知肝势正盛，深刻克制脾土，虽然说补脾，怎么能抵挡其正盛之势呢？纵使土能生金，金受到火克，也是所得不足以补偿所失。这就是不补土而补水的原因。
有人怀疑木旺补水，恐怕水生木而使木更旺，所以听到只泻火不补水的说法，欣然听从。殊不知木已经旺了，何须等待水生呢？况且水虚，即使峻补尚且不能恢复其本气，哪有余力生木呢？如果能生木，就能胜火了。又有人说：补水，是想让水不去消耗金（母），水不食金，则金气恢复了。怎知火克金，土不能生金，金的虚损已极，尚且不能自给，水虽然想“食”金（生水需耗金之气以相生，此处借喻关系），有什么可供给的呢？如果这样，那么金虚就不是由于火的克制，而是由于水的消耗了，这合乎情理吗？纵使水不消耗金，金也未必能恢复正常。文中“金不得平木”一句，多了一个“不”字。之所以泻火补水，正是为了让金能够平抑木，“不”字应当删去。“不能治其虚，何问其余？”这里的虚指的是肺虚。泻火补水，使金能够平抑木，这正是所谓能治疗其虚证。不补土，不补金，而是泻火补水，使金自行平复，这是方法的巧妙和精妙之处。如果不能通晓此法，不能治疗此虚证，那么就不用问其他事情了，必然是无能之人。所以说：“不能治其虚，何问其余？”至于上文所说的金木水火土互相平衡的意义，不需解释自然明了，这里就不再赘述了。越人是亚圣般的人物，论述达到这种境界，岂敢不恭敬？只是痛恨解说者曲解了它，所以加以辨析。
The Seventy-Fifth Difficulty states: The Classic says, "The East is excess, the West is deficiency; drain the South, tonify the North." What does this mean? The answer is: Metal, Wood, Water, Fire, and Earth should balance each other.
The East corresponds to Wood, and the West to Metal. If Wood desires to be excessive, Metal should regulate it; if Fire desires to be excessive, Water should regulate it; if Earth desires to be excessive, Wood should regulate it; if Metal desires to be excessive, Fire should regulate it; if Water desires to be excessive, Earth should regulate it. The East corresponds to the Liver (Gan), indicating Liver excess; the West corresponds to the Lung (Fei), indicating Lung deficiency. The treatment should drain Southern Fire and tonify Northern Water. The South corresponds to Fire, which is the Son of Wood; the North corresponds to Water, which is the Mother of Wood. Water overcomes Fire. The Son can make the Mother full, and the Mother can make the Son empty. Therefore, by draining Fire and tonifying Water, the intention is to prevent Metal from regulating Wood (i.e., to relieve the excessive constraint of Metal on Wood). The Classic states: "If one cannot treat the deficiency, why ask about the rest?" This refers to this principle. Whenever I read this, I cannot help but sigh at Yuèrén's (Qin Yueren) ability to grasp the intent of the Classic, while lamenting that later generations have lost this intent.
Ancient sages said, when studying books, one should not first look at annotations. Instead, repeatedly recite and savor the original text until one has new insights, then cross-reference with annotations. Thus, the meaning of the Classic will become clear, and one will not be obscured by others' theories. If one looks at annotations first, their views will dominate one's mind, leaving no room for new insights. I have always admired this teaching and benefited greatly from it. Moreover, this chapter in the *Nan Jing* (Classic of Difficult Issues) is comprehensive and pure, serving as a model for all ages. Can the numerous discussions of later generations be trusted?
Generally, "excess is treated by draining, deficiency is treated by tonifying" is the standard approach; "drain the Son of an excess pattern, tonify the Mother of a deficiency pattern" is also a standard approach. Everyone knows this. Now, with Liver excess and Lung deficiency, instead of draining the Lung, one drains the Heart. This is known to people. However, instead of tonifying the Lung or the Spleen, one tonifies the Kidney. This is unknown to most, known only to Yuèrén. Regarding "the Son can make the Mother full, and the Mother can make the Son empty," from a common perspective, one might say: Heart Fire excess causes Liver Wood to be excess; this is the Son making the Mother full. Spleen Earth deficiency causes Lung Metal to be deficient; this is the Mother making the Son empty. Heart Fire excess is indeed due to its own hyperactivity; Spleen Earth deficiency is due to being constrained by Liver Wood. The method should be to drain the Heart and tonify the Spleen, so that both Liver and Lung would be balanced. Yuèrén, however, did not do this. When he said "the Son can make the Mother full," the Son is Fire and the Mother is Wood, which aligns with common sense. But when he said "the Mother can make the Son empty," the Mother is Water and the Son is Wood, which differs from common sense. Thus, he stated: Water is the Mother of Wood. The phrase "the Son can make the Mother full" explains the etiology; the phrase "the Mother can make the Son empty" explains the therapeutic method. His meaning is: Fire is the Son of Wood. The Son assists the Mother, causing it to become excessive and diseased. How should this be handled? Only through the treatment of tonifying Water and draining Fire.
What does tonifying Water mean? Since Water is the Mother of Wood, if one tonifies the deficiency of Water, enabling its strength to overcome Fire, the Fire qi will retreat, and consequently, the Wood qi will also retreat. This embodies the meaning of "the Mother can make the Son empty," which is referred to as "treating without treating" (indirect treatment). (Note: The character "deficiency" here differs from "deficiency due to loss of essence and Qi" in the *Jing Mai* chapter. In the latter, deficiency refers to depletion of true Yin leading to weakness; here, it refers to suppressing excess to induce a state of relative emptiness/weakness.) If one argues otherwise, to which organ system should "the Mother can make the Son empty" be attributed? To the Spleen and Lung? If so, why not tonify the Spleen? The principle of the Five Elements dictates that what is feared is what overcomes it. Now, Fire is too strong, and Water is too deficient. What does Fire fear? Precisely because it fears nothing, it becomes even stronger and uncontrolled. Unless one nourishes Water to overcome it, who can overcome it? The three characters "Water overcomes Fire" are the key implication of Yuèrén, to be observed carefully, not lightly dismissed. Although both draining Fire and tonifying Water are mentioned, the crux lies in tonifying Water. Later commentators claimed: "Only drain Fire, do not tonify Water." Or they said: "Draining Fire is equivalent to tonifying Water." Is this not a great deviation from the intent of Yuèrén and the Classic? If tonifying Water were truly unnecessary, the Classic would not have said "tonify the North," nor would Yuèrén have said "tonify Water." That said, if Water is not deficient and Fire alone is violently hyperactive, it is indeed possible to proceed without tonifying Water. But if Fire hyperactivity was caused initially by Water deficiency, can one skip tonifying Water? If Water is deficient and Fire is hyperactive, and one does not tonify Water, the medicine may temporarily suppress symptoms, but they will recur after the medicine wears off. This will continue indefinitely year after year. How can the root be eradicated? Even bitter-cold herbs, which generally suppress Yang and support Yin, merely drain Fire pathogenic factors. They are ultimately not the proper herbs for the Kidney and cannot nourish the True Yin of the North. To benefit Yin, herbs such as Dihuang (Rehmanniae Radix) and Huangbai (Phellodendri Cortex) are indispensable.
Furthermore, there are two causes for Liver excess: First, Heart assistance makes Liver excess; second, the Lung's inability to control Liver makes Liver excess. There are also two causes for Lung deficiency: First, Heart overcoming Lung makes Lung deficient; second, the Spleen being controlled by Liver prevents it from generating Lung, making Lung deficient. Now, by tonifying Water and draining Fire, Fire retreats, weakening Wood qi. Additionally, Metal is no longer overcome by Fire and can constrain Wood, so the East (Liver) is no longer in excess. With Metal qi balanced, Earth is no longer overcome by Wood and can generate Metal, so the West (Lung) is no longer deficient. If one speaks according to "tonify the Mother in deficiency patterns," Lung deficiency should be treated by tonifying the Spleen. But how can one ignore that Liver qi is currently vigorous and deeply constrains Earth? Even if one tonifies the Spleen, how can it withstand the vigorous Liver? Even if Earth generates Metal, if Metal is overcome by Fire, the gain will not compensate for the loss. This is why one tonifies Water instead of Earth.
Some suspect that tonifying Water when Wood is hyperactive might cause Water to generate more Wood, making Wood even stronger. Thus, they happily accept the theory of "only draining Fire, not tonifying Water." Little do they know that Wood is already hyperactive; why wait for generation? Moreover, Water is deficient; even with potent tonification, it struggles to restore its original qi, let alone have surplus energy to generate Wood. If it could generate Wood, it would already be able to overcome Fire. Others argue: Tonifying Water aims to prevent Water from consuming its Mother (Metal). If Water does not consume Metal, Metal qi returns. How can they not realize that Fire overcomes Metal, and Earth fails to generate Metal due to Liver constraint? Metal's deficiency is extreme, unable to sustain itself. Even if Water wishes to "consume" Metal (in the generative cycle context, though technically Water is generated by Metal, the argument implies resource competition or lack of support), where is there anything to give? If this were true, Metal's deficiency would not be due to Fire's constraint but due to Water's consumption. Is this logical? Even if Water does not consume Metal, Metal may not necessarily recover. The phrase "Metal does not regulate Wood" contains an extra "not." The reason for draining Fire and tonifying Water is precisely to enable Metal to regulate Wood. The word "not" should be deleted. "If one cannot treat the deficiency, why ask about the rest?" Here, "deficiency" refers to Lung deficiency. Draining Fire and tonifying Water enables Metal to regulate Wood, which is exactly what is meant by "being able to treat the deficiency." Not tonifying Earth or Metal, but rather draining Fire and tonifying Water to allow Metal to self-balance, is the cleverness and subtlety of this method. If one cannot understand this method and cannot treat this deficiency, there is no need to ask about other matters; such a person is undoubtedly incompetent. Hence, "If one cannot treat the deficiency, why ask about the rest?" As for the meaning of Metal, Wood, Water, Fire, and Earth balancing each other mentioned earlier, it is self-evident and needs no explanation, so it is omitted here. Yuèrén is a near-sage. When his discourse reaches this level, how can one not bow in respect? I only regret that commentators have distorted it, hence this clarification.