李东垣曰∶古之至人，穷阴阳之造化，究乎生死之际，所着《内经》，悉言人以胃气为
本。盖人受水谷之气以生，所谓元气、谷气、营气、卫气、清气、春升生发之气，此六者以
谷气上行，皆胃气之别称也。使谷气不得升浮，生长之令不行，则无阳以护其营卫，不任风
寒，乃生寒热，皆脾胃之气不足所致也。然而与外感风寒之证颇同而理异。内伤脾胃，乃伤
其气；外伤风寒，乃伤其形。伤外为有余，有余者泻之；伤内为不足，不足者补之。汗之、
下之、吐之、克之，皆泻也；温之、和之、调之、养之，皆补也。内伤不足之病，苟误认作
外感有余之病而反泻之，则虚其虚也。《难经》曰∶实实虚虚，损不足而益有余，如此死者
，医杀之耳。然则奈何？曰∶惟当以甘温之剂，补其中，升其阳，甘寒以泻其火则愈。《内
经》曰∶劳者温之，损者温之。盖温能除大热，大忌苦寒之剂泻胃土耳。今立补中益气汤。
又曰∶夫喜怒不节，起居不时，有所劳伤，皆损其气，气衰则火旺，火旺则乘其脾土。
脾主四肢，故困热无气以动，懒于言语，动作喘乏，表热自汗，心烦不安。当病之时，宜安
心静坐以养其气，以甘寒泻其热火，以酸味收其散气，以甘温补其中气。经言劳者温之，损
者温之是也。《金匮要略》曰∶平人脉大为劳，虚极亦为劳。夫劳之为病，其脉浮大，手足
烦热，春夏剧，秋冬火差，以黄 建中汤治之，此亦温之之意也。
又曰∶脾胃受劳役之疾，饮食又复失节，耽病日久，事息心安，饱食太甚，病乃大作。
故内伤饮食，则亦恶风寒，是营卫失守，皮肤间无阳以滋养，不能任风寒也。皮毛之绝，则
心肺之本亦绝矣。盖胃气不升，元气不至，无以滋养心肺，乃不足之证也。计受病不一，饮
食失节，劳役所伤，因而饱食，内伤者极多，外伤者间而有之。举世医者，往往将元气不足
之证，便作外伤风寒表实之证，而反治心肺，是重绝其表也，安得不死乎？若曰不然，请以
众人之耳闻目见者证之。向者壬辰改元，京师戒严，迨三月下旬，受敌者凡半月，解围之后
，都人之不受病者，万无一二，既病而死者，继踵而不绝，都门十有二所，每日各门所送，
多者二千，少者不下一千，似此者几三月。此百万人岂俱感风寒外伤者耶？大都人在围城中
，饮食失节，劳役所伤，不待言而知。由其朝饥暮饱，起居不时，寒温失所，动经三两月，
胃气亏之久矣，一旦饱食太过，感而伤人，而又调治失宜，其死也无疑矣。非惟大梁为然，
远在真佑、兴定间，如东平，如太原，如凤翔，解围之后，病伤而死，无不皆然。余在大梁
，凡所亲见，有发表者，有以巴豆推之者，有以承气汤下之者，俄而变结胸发黄，又以陷胸
汤丸及茵陈汤下之，无不死者。盖初非伤寒，以调治差误，变而似真伤寒之证，皆药之罪也
。往者不可追，来者犹可及，辄以生平已试之效，着《内外伤辨论》一篇，推明前哲之余论
，历举近事之变故，庶几同志者，审其或中，触类而长之，免后人之横夭耳。
东垣辨气少气盛曰∶外伤风寒者，其气壅盛而有余；内伤饮食劳役者，其口鼻中气皆短
促不足以息。何以分之？盖外伤风寒者，心肺元气初无减损，又添邪气助之，使鼻气壅塞不
利，面赤，其鼻中气不能出，并从口出，但发一言，必前轻后重，其声壮厉而有力者，乃有
余之验也。伤风则决然鼻流清涕，其声嗄，其言响如从瓮中出，亦前轻而后重，高揭而有力
，皆气盛有余之验也。内伤饮食劳役者，心肺之气先损，为热所伤，热既伤气，四肢无力以
动，故口鼻中皆短气少气，上喘懒语，人有所问，十不欲对其一，纵勉强答之，其气亦怯，
其声亦低，是其气短少不足之验也。明白如此，虽妇人女子亦能辨之，岂有医者反不能辨之
乎？
东垣辨头痛曰∶内证头痛，有时而作，有时而止，外证头痛，常常有之，直须传入里实
方罢，此内外证之不同也。
李东垣说：古代的圣人，探究阴阳的造化规律，研究生死的界限，所著的《内经》中，都强调人以胃气为根本。大概人依靠水谷的精微之气而生存，所谓的元气、谷气、营气、卫气、清气、春升生发之气，这六者都是随着谷气上行，都是胃气的别称。如果谷气不能上升浮越，生长化育的机能就不能正常行使，就没有阳气来护卫营卫，无法抵御风寒，从而产生寒热症状，这都是脾胃之气不足所致。然而这与外感风寒的证候颇为相似，但机理不同。内伤脾胃，是损伤了正气；外伤风寒，是损伤了形体。伤于外邪属于有余（实证），有余的应当用泻法；伤于内因属于不足（虚证），不足的应当用补法。发汗、攻下、催吐、克削，都属于泻法；温养、调和、调理、滋养，都属于补法。内伤不足的疾病，如果错误地当作外感有余的疾病而反用泻法，就会使虚者更虚。《难经》说：实证误用泻法使其更实，虚证误用补法使其更虚，损害不足的正气而增加有余的邪气，像这样导致死亡的，是医生杀死了病人。那么该怎么办呢？回答说：只应当用甘温的药剂，补益其中气，升举其阳气，用甘寒的药来清泻火热，病就能痊愈。《内经》说：劳损的病要用温法治疗，亏损的病要用温法治疗。大概温能除大热，最忌讳使用苦寒的药剂来泻胃气。现在制定补中益气汤。
又说：喜怒没有节制，起居没有定时，有所劳伤，都会损伤正气，气衰则火旺，火旺则会乘袭脾土。脾主四肢，所以感到困倦发热，没有力气活动，懒于说话，动作时气喘乏力，体表发热自汗，心烦不安。在患病的时候，应当安心静坐以涵养正气，用甘寒的药清泻热火，用酸味的药收敛散失的气，用甘温的药补益中气。经文所说的“劳者温之，损者温之”就是这个意思。《金匮要略》说：平时脉象大为劳病，极度虚弱也是劳病。劳病这个疾病，脉象浮大，手足烦热，春夏季节加重，秋冬季节火热减退，用黄芪建中汤治疗，这也是温补的意思。
又说：脾胃受到劳役的疾病，饮食又再次失去节制，沉溺于病痛日久，事情平息心情安定时，饱食过度，病情就大作。所以内伤饮食，也会恶风寒，这是营卫失守，皮肤间没有阳气来滋养，不能承受风寒。皮毛的屏障功能丧失，心肺的根本也就丧失了。因为胃气不升，元气不到达，无法滋养心肺，这是不足的证候。计算受病的途径不一，饮食失节，劳役所伤，因而饱食，内伤者极多，外伤者偶尔也有。世间的医生，往往将元气不足的证候，便当作外伤风寒表实的证候，反而治疗心肺，这是重重地断绝体表阳气，怎么能不死呢？如果说不是这样，请允许我用众人耳闻目睹的事实来证明。此前壬辰年改元，京城戒严，等到三月下旬，遭受敌人围困共半个月，解围之后，城里人没有生病的，万无一二，既然后生病而死的人，接踵而至络绎不绝，城门十二处，每天各门送来的尸体，多的两千，少的不下一千，像这种情况持续了近三个月。这一百万人难道都感受了风寒这种外邪吗？大抵人在围城中，饮食失节，劳役所伤，是不言而喻的。由于他们早晨饥饿晚上饱食，起居没有定时，寒暖失调，动辄两三个月，胃气亏损已经很久了，一旦饱食太过，感邪伤人，而又调治不当，他们的死亡是毫无疑问的。不仅大梁是这样，远在真佑、兴定年间，像东平，像太原，像凤翔，解围之后，因病伤而死，无不都是如此。我在大梁，凡是亲眼所见的，有使用发表药的，有用巴豆推荡的，有用承气汤攻下的，不久变成结胸发黄，又用陷胸汤丸及茵陈汤攻下，没有不死的。起初并非伤寒，因为调治差错失误，变化得像真正的伤寒证候，这都是药物的罪过。过去的事情无法追回，未来的事情还可以补救，于是将我平生已验证有效的经验，写成《内外伤辨论》一篇，推明前代哲人的余论，列举近期事件的变故，希望志同道合的人，审慎判断其中是否有道理，触类旁通加以发展，以免后人横遭夭折罢了。
李东垣辨别气少与气盛说：外伤风寒的人，其气壅盛而有余；内伤饮食劳役的人，其口鼻中的气都短促不足以呼吸。如何区分它们？大概外伤风寒的人，心肺元气起初并没有减损，又加上邪气助长它，使得鼻气壅塞不利，面色发红，鼻中的气不能排出，并从口中呼出，只要说一句话，必定前轻后重，声音壮厉有力的，这是有余的验证。伤风则必然鼻涕流清涕，声音嘶哑，说话响声如同从瓮中发出，也是前轻而后重，高声揭起而有力，都是气盛有余的验证。内伤饮食劳役的人，心肺之气先受损，被热邪所伤，热既损伤气，四肢无力活动，所以口鼻中皆短气少气，上气喘促懒于言语，别人有所问，十个里面不想回答一个，纵然勉强回答，气息也怯弱，声音也低微，这是气短少不足的验证。像这样明白清楚，即使是妇女女子也能辨别，哪有医生反而不能辨别的呢？
李东垣辨别头痛说：内伤引起的头痛，有时发作，有时停止；外感引起的头痛，常常存在，直到传入里实证才停止，这是内外证的不同之处。
Li Dongyuan said: The ancient sages thoroughly investigated the creation and transformation of Yin and Yang, and explored the boundaries between life and death. In the *Neijing* (Inner Canon), it is consistently stated that humans rely on Stomach Qi (Stomach Energy) as their foundation. Essentially, humans derive life from the Qi of water and grain. The so-called Yuan Qi (Original Qi), Gu Qi (Grain Qi), Ying Qi (Nutritive Qi), Wei Qi (Defensive Qi), Qing Qi (Clear Qi), and the Spring-rising generating Qi are all referred to as alternative names for Stomach Qi, as they ascend with the Grain Qi. If the Grain Qi fails to ascend and float, the function of growth and development cannot be executed. Consequently, there is no Yang Qi to protect the Ying and Wei Qi, leaving the body unable to withstand Wind-Cold, thereby generating symptoms of chills and fever. These are all caused by a deficiency in Spleen and Stomach Qi. However, this condition is quite similar to exterior syndromes caused by Wind-Cold invasion, yet the underlying mechanism differs. Internal injury to the Spleen and Stomach damages the Qi (Zheng Qi/Righteous Qi); external injury by Wind-Cold damages the physical form. Injury from external pathogens constitutes an Excess syndrome (Shi Zheng), which should be treated with draining methods; injury from internal causes constitutes a Deficiency syndrome (Xu Zheng), which should be treated with tonifying methods. Sweating, purging, vomiting, and reducing are all draining methods; warming, harmonizing, regulating, and nourishing are all tonifying methods. For diseases of internal deficiency, if mistakenly identified as external excess and treated with draining methods, the deficiency will be exacerbated. The *Nan Jing* (Classic of Difficult Issues) states: "Making the excess more excess and the deficiency more deficient, damaging what is insufficient and benefiting what is already excessive"—such deaths are caused by the physician's killing of the patient. So, what should be done? The answer is: One must use sweet-warm formulas to tonify the Middle Jiao (Middle Burner) and raise the Yang Qi, and use sweet-cold herbs to clear and drain the Fire, after which the illness will heal. The *Neijing* states: "For exhaustion, use warmth; for loss, use warmth." Warmth can eliminate great heat; therefore, bitter-cold formulas that drain Stomach Qi are strictly contraindicated. I have now established the Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction).
Furthermore, he stated: Unregulated emotions and irregular daily routines, along with various forms of overexertion, all damage the Qi. When Qi declines, Fire flares up; when Fire flares, it attacks the Spleen and Earth. Since the Spleen governs the four limbs, one feels fatigued and hot, lacks energy to move, is reluctant to speak, experiences panting and fatigue upon movement, has surface heat and spontaneous sweating, and feels restless and uneasy. During the onset of the disease, one should sit quietly with a calm mind to nurture the Qi, use sweet-cold herbs to drain the Fire-Heat, use sour-flavored herbs to astringe the scattered Qi, and use sweet-warm herbs to tonify the Middle Qi. This aligns with the scriptural teaching: "For exhaustion, use warmth; for loss, use warmth." The *Jinkui Yaolue* (Essential Prescriptions of the Golden Cabinet) states: "A normal person with a large pulse suffers from Lao (chronic depletion/exhaustion); extreme weakness also indicates Lao." In cases of Lao disease, the pulse is floating and large, with vexation and heat in the hands and feet; symptoms worsen in spring and summer and improve in autumn and winter. It is treated with Huangqi Jianzhong Tang (Astragalus Decoction to Establish the Middle), which embodies the principle of warming.
He further stated: When the Spleen and Stomach suffer from labor-induced ailments, and dietary habits become irregular again, lingering in illness for a long time, once affairs cease and the mind calms, excessive eating causes the disease to flare up severely. Thus, internal injury from diet also leads to aversion to wind and cold. This is due to the failure of Ying and Wei Qi to guard the exterior, where a lack of Yang Qi in the skin prevents nourishment and resistance to Wind-Cold. The destruction of the hair and skin barrier implies the destruction of the root of the Lung and Heart. Because Stomach Qi does not ascend and Yuan Qi does not reach, the Lung and Heart cannot be nourished, resulting in a deficiency syndrome. The causes of disease vary: irregular diet, injury from labor, and subsequent overeating lead to many cases of internal injury, while external injuries occur occasionally. Physicians of the world often mistake conditions of insufficient Yuan Qi for exterior excess syndromes caused by Wind-Cold, and incorrectly treat the Lung and Heart, thereby doubly severing the exterior Yang. How could such patients not die? If you say otherwise, let me prove it with what people have seen and heard. Previously, during the change of era name in the Renchen year, the capital was under siege. By late March, after being besieged for half a month, upon relief, almost none of the city dwellers escaped illness, and those who fell ill died in succession. At the twelve gates of the capital, the number of bodies delivered daily ranged from over two thousand to at least one thousand, continuing for nearly three months. Did all these million people contract external Wind-Cold? It goes without saying that people within the besieged city suffered from irregular diet and labor-induced injury. Due to morning hunger and evening gluttony, irregular routines, and exposure to improper temperatures for months, their Stomach Qi had been depleted for a long time. Once they ate too much, became infected, and received improper treatment, their death was inevitable. This was not only true for Daliang (Kaifeng); even during the Zhenyou and Xingding eras, in places like Dongping, Taiyuan, and Fengxiang, after sieges were lifted, deaths from illness and injury were universal. While in Daliang, I personally witnessed cases where physicians used dispersing agents, Cathartics like Radix Euphorbiae Pekingensis (Badou), or Chengqi Tang (Chengqi Decoction) for purging. Soon, patients developed Jie Xiong (Chest Binding) and jaundice, leading to further treatments with Xin Xiong Tang Wan (Xin Xiong Decoction Pills) and Yinchen Tang (Artemisia Capillaris Decoction) for purging, resulting in certain death. Initially, these were not Shanghan (Cold Damage) cases; due to diagnostic and therapeutic errors, the condition transformed to resemble true Shanghan. This was the fault of the medication. Past events cannot be retrieved, but future ones can be addressed. Therefore, based on my lifelong validated experience, I wrote the essay "Bian Lun Nei Wai Shang" (Discrimination between Internal and External Injury), elucidating the remaining theories of former sages and citing recent incidents, hoping that colleagues may judge its validity, extend understanding through analogy, and prevent premature death in future generations.
Li Dongyuan distinguished between Scanty Qi and Abundant Qi: In exterior Wind-Cold invasion, Qi is congested and abundant (Excess); in internal injury from diet and labor, Qi at the mouth and nose is short and rapid, insufficient for breathing. How to differentiate them? In exterior Wind-Cold, the Yuan Qi of the Lung and Heart is initially undiminished, and the pathogenic Qi adds to it, causing nasal congestion and obstruction, reddish face, and inability to exhale through the nose, forcing exhalation through the mouth. Speech begins lightly and ends heavily, with a strong, vigorous, and powerful voice, indicating an Excess syndrome. In Wind Strike, clear nasal discharge occurs, the voice is hoarse, and speech sounds resonant as if from a jar, also beginning lightly and ending heavily, with high-pitched and powerful tones, confirming Qi abundance and Excess. In internal injury from diet and labor, the Qi of the Lung and Heart is first damaged by Heat. Since Heat damages Qi, the limbs lack strength to move. Thus, Qi at the mouth and nose is short and scant, accompanied by upper panting, reluctance to speak, and a desire to avoid answering questions (one in ten responses). Even if forced to answer, the breath is timid and the voice low, confirming Qi shortage and Deficiency. Such clarity allows even women to distinguish these conditions; how could physicians fail to do so?
Li Dongyuan differentiated headache: Internal headaches come and go intermittently; external headaches persist constantly until they transmit into interior Excess syndromes, at which point they cease. This marks the difference between internal and external syndromes.