经云∶病有逆从者，以病有微甚；病有微甚者，以证有真假，不知寒热有真假。真者正
治，
知者无难，假者反治，乃为难耳。如寒热之真假者，真寒则脉沉而细，或弱而迟，为厥逆，
为呕吐，为腹痛，为飧泄下利，为小便频。即发热必欲得衣，此浮热在外，沉寒在里也。真
热则脉数有力，滑大而实，为烦躁喘满，为声音壮厉，或大便秘结，或小便赤涩，或发热掀
衣，或胀痛热渴，此皆真病。真寒者，宜温其寒；真热者，宜解其热，是当正治也。至若假
寒者，火极似水，阳证似阴也，外虽寒而内则热，脉数而有力，或沉而鼓击，或身恶衣，或
便热秘结，或烦渴引饮，或肠垢臭秽，此则恶寒非寒，明是热证，所谓热极反兼寒化，亦曰
阳盛格阴也。假热者，水极似火，阴证似阳也。外虽热而内则寒，脉微而弱，或数而虚，或
浮大无根，或弦芤断续，身虽炽热而神色自静，语虽谵妄而声音则微，或虚狂起倒而禁之则
止，或蚊迹假斑而涉红细碎，或喜冷水而所饮不多，或舌面赤而衣被不彻，或小水多利而大
便不结。此则恶热非热，明是寒证，所谓寒极又兼热化，亦曰阴盛格阳也，此皆假病假寒者
。清其内热，内清则浮阴去舍矣。假热者，温其真阳，中温则虚火归元矣，是当从治者也。
又如虚热实热，实则泻之，虚则补之，此不易之法也。然至虚有盛候，则有假实矣；大实有
羸状，则有假虚矣。总之虚者，正气虚也，为色惨形瘦，为神衰气怯，或自汗不收，或二便
不禁，或梦遗精滑，或呕吐鬲塞，或久病攻多，或短气似喘，或劳伤过度。或暴困失志，虽
外证似实，而脉弱无神者，皆虚证之当补也。实者邪气实也，或外闭于经络，或内结于脏腑
，或气壅而不行，或血流而凝滞，必脉病俱盛，乃实证之当攻也。然而虚实之间，最多疑似
，有不可不辨其真者。如经云∶邪气盛则实，精气夺则虚，此虚实之大法也。设有人焉，正
已夺而邪方盛者，将顾其正而补之乎？抑先其邪而攻之乎？见有不的，则死生系之，此其所以
宜慎也。夫正者本也，邪者标也。若正气既虚，则邪气虽盛，亦不可攻，盖恐邪未去而先脱
，呼吸变生，则措手无及。故治虚邪者，先当顾正气，正气存，则不至于害。且补中自有攻
意，未有正气复而邪犹不退者，此治虚之道也。若正气无损者，邪气虽微，自不宜补，盖补
之则正无与，而邪反盛，适足藉寇兵而 盗粮。故治实证者，必直去其邪，邪去则身安，但
法贵精专，使致速效。治实之道也。要之能胜攻者，便是实证，不能胜攻者，便是虚证。惟
是假虚之证不多见，而假实之证最多也；假寒之证不难治，而假热之证治多误也。世有不明
真假本末，而云知医，我敢轻许乎哉？
《黄帝内经》说：疾病有顺证和逆证的区别，是因为病情有轻微和严重的不同；病情有轻微和严重的区别，是因为症状有真象和假象的不同。如果不了解寒热症状的真假，治疗就会出错。对于真病采用正治法（即寒者热之、热者寒之），懂得辨证的医生处理起来并不困难；而对于假象采用反治法（即热因热用、寒因寒用），这才是难点所在。
以寒热的真假为例：真寒证表现为脉象沉细，或者微弱迟缓，出现四肢厥冷、呕吐、腹痛、完谷不化的泄泻或下利、小便频数等症状。即使伴有发热，患者也一定想要穿衣保暖，这是浮热在体表，而沉寒在体内的表现。真热证则表现为脉象数而有力，滑大且实，出现烦躁、气喘胸闷，声音洪亮粗厉，或者大便秘结，或者小便短赤涩痛，或者发热时掀开衣被，或者胀痛、口渴喜冷饮，这些都是真正的热病。真寒证，应当用温法来散寒；真热证，应当用清法来解热，这属于正治法。
至于假寒证，是火极似水，阳证表现出阴证的特征。虽然体表感觉寒冷，但体内却是热的，脉象数而有力，或者沉取时搏动有力如鼓击，或者身体厌恶穿衣，或者大便燥结灼热，或者心烦口渴想喝水，或者排泄物秽臭，这都是恶寒并非真寒，明明是热证，所谓“热极反兼寒化”，也称为“阳盛格阴”。
假热证，是水极似火，阴证表现出阳证的特征。虽然体表感觉发热，但体内却是寒的，脉象微细无力，或者数而虚软，或者浮大无根，或者弦细芤脉且断续不匀，身体虽然炽热但神色安静，说话虽然谵妄但声音微弱，或者虚性狂躁起倒但制止后即止，或者皮疹像蚊迹般的假斑且颜色红而细碎，或者喜欢喝冷水但饮用量不多，或者舌面发红但衣被穿得严实，或者小便多而通畅但大便不干燥。这都是恶热并非真热，明明是寒证，所谓“寒极又兼热化”，也称为“阴盛格阳”，这些都属于假病和假寒证。对于假寒证，应清除内部的热邪，内热清了，浮游的阴寒之气自然离去。对于假热证，应温补真正的阳气，中焦温暖了，虚浮的火气自然回归本源，这属于从治法（反治法）。
又如虚热和实热，实证用泻法，虚证用补法，这是不变的原则。然而，极度虚弱可能出现盛实的征候，这就是假实；极度实邪可能出现羸弱的形态，这就是假虚。总之，虚证是正气虚弱，表现为面色惨淡、形体消瘦、精神萎靡、气息怯弱，或者自汗不止，或者大小便失禁，或者梦遗滑精，或者呕吐膈塞不通，或者久病攻伐过度，或者气短似喘，或者劳伤过度，或者突然困顿意志消沉。虽然外部症状看似实证，但脉象虚弱无神的，都是应当用补法的虚证。实证是邪气盛实，或者外邪闭塞经络，或者内邪结聚脏腑，或者气机壅滞不行，或者血液凝滞，必须脉象和病症都呈现盛实状态，才是应当用攻法的实证。
然而，虚实之间，最容易混淆，有不分辨清楚真假的不可之处。正如经文所说：“邪气盛则实，精气夺则虚”，这是辨别虚实的大法。假设有人，正气已经亏损而邪气正盛，是应该顾护正气先进行补益呢？还是应该先祛除邪气进行攻伐呢？如果判断不准确，就关系到生死，所以对此必须谨慎。正气是本，邪气是标。如果正气已经虚弱，那么即使邪气很盛，也不可攻伐，因为恐怕邪气未去而正气先脱，呼吸间发生变故，就来不及措手了。所以治疗虚实夹杂的病，首先应当顾护正气，只要正气存在，就不会造成危害。而且补益之中自有攻邪之意，没有正气恢复而邪气还不退去的，这就是治疗虚证的方法。如果正气没有损伤，即使邪气轻微，也不宜补益，因为补益会导致正气无所依附（或理解为补药滋腻碍胃，正气无法运化），反而使邪气更盛，这无异于借给敌人兵器、送给盗贼粮食。所以治疗实证，必须直接去除邪气，邪气去除了身体就安泰了，但治疗方法贵在精专，以求速效，这就是治疗实证的方法。总而言之，能够耐受攻伐的，就是实证；不能耐受攻伐的，就是虚证。只是假虚的证候不多见，而假实的证候最多；假寒的证候不难治疗，而假热的证候治疗失误最多。世上那些不明白真假本末却声称懂医的人，我敢轻易认可吗？
The *Yellow Emperor's Inner Canon* states: Diseases have favorable (conforming) and unfavorable (contrary) courses, due to the slightness or severity of the disease; the slightness or severity of the disease is determined by the truth or falsity of the symptoms. If one does not understand the truth or falsity of cold and heat, errors in treatment will occur. For true conditions, direct treatment (Zheng Zhi, treating cold with heat and heat with cold) is applied; for those who understand this, it is not difficult. For false conditions, contrary treatment (Fan Zhi, such as treating heat with heat or cold with cold) is required, which is the difficult part.
Regarding the truth or falsity of cold and heat: A true cold condition presents with a deep and fine pulse, or weak and slow, accompanied by cold extremities (Jue Ni), vomiting, abdominal pain, undigested food diarrhea (Sun Xie), loose stools, and frequent urination. Even if fever is present, the patient desires to wear clothes; this indicates floating heat on the exterior and sinking cold in the interior. A true heat condition presents with a rapid and forceful pulse, slippery, large, and excess; accompanied by restlessness, panting, and chest fullness, loud and harsh voice, constipation, or dark and scanty urine, or fever where the patient throws off covers, or distending pain and thirst for cold drinks. These are all true diseases. True cold should be treated with warming methods to dispel cold; true heat should be treated with clearing methods to resolve heat. This is direct treatment.
As for false cold, it is extreme fire resembling water, where Yang conditions resemble Yin. Although the exterior feels cold, the interior is hot. The pulse is rapid and forceful, or deep but beating strongly like a drum, or the body dislikes clothing, or stool is hot and constipated, or there is irritability and thirst with desire to drink, or intestinal discharge is foul-smelling. This is aversion to cold that is not true cold, clearly a heat condition. It is called "extreme heat assuming cold transformation" or "Yang excess repelling Yin."
False heat is extreme water resembling fire, where Yin conditions resemble Yang. Although the exterior feels hot, the interior is cold. The pulse is faint and weak, or rapid but empty, or floating and large without root, or wiry, knotted, intermittent. The body may be burning hot but the spirit and expression remain calm; speech may be delirious but the voice is weak; or there is false mania and tumbling that stops when restrained; or skin lesions resemble mosquito bites with small, fragmented red spots; or there is a preference for cold water but little is drunk; or the tongue surface is red but the patient keeps warm clothing/bedding on; or there is frequent urination but no constipation. This is aversion to heat that is not true heat, clearly a cold condition. It is called "extreme cold assuming heat transformation" or "Yin excess repelling Yang." These are false diseases and false cold. For false cold, clear the internal heat; once the internal heat is cleared, the floating Yin will depart. For false heat, warm the true Yang; once the middle warmer is warmed, the deficient fire will return to its origin. This is contrary treatment (Cong Zhi).
Similarly, regarding deficient heat and excess heat: Excess is purged, deficiency is tonified. This is an unchangeable principle. However, extreme deficiency may present with excess signs, which is false excess; extreme excess may present with emaciated signs, which is false deficiency. In summary, deficiency refers to the deficiency of Zheng Qi (Upright Qi), manifesting as a gloomy complexion and emaciated form, mental fatigue and timid qi, spontaneous sweating that does not stop, incontinence of urine and feces, nocturnal emission and seminal leakage, vomiting and diaphragmatic obstruction, excessive purgation during long-term illness, shortness of breath resembling asthma, overexertion, or sudden exhaustion and loss of will. Although external signs may resemble excess, if the pulse is weak and lacks spirit, these are all deficiency conditions requiring tonification. Excess refers to the excess of Xie Qi (Pathogenic Factors), whether blocking meridians externally or knotting in organs internally, or qi stagnation and blood stasis. Only when both pulse and disease signs are robust is it an excess condition requiring attack/purging.
However, between deficiency and excess, there is much ambiguity, making it essential to distinguish the truth. As the Canon states: "When pathogenic factors are abundant, it is excess; when essence and qi are depleted, it is deficiency." This is the general rule for deficiency and excess. Suppose a person whose Zheng Qi has been depleted while Xie Qi is currently abundant: Should one protect the Zheng Qi and tonify first? Or should one attack the Xie Qi first? If the judgment is not accurate, life and death depend on it; thus, caution is necessary. Zheng Qi is the root; Xie Qi is the branch. If Zheng Qi is already deficient, even if Xie Qi is abundant, one must not attack, for fear that the Xie Qi will not be expelled before the Zheng Qi collapses, leading to fatal changes in breathing that cannot be managed. Therefore, in treating mixed deficiency and excess, one must first protect the Zheng Qi. If Zheng Qi is preserved, harm will not occur. Moreover, tonification contains the intent of purging; there is no case where Zheng Qi recovers while Xie Qi remains. This is the method for treating deficiency. If Zheng Qi is undamaged, even if Xie Qi is slight, one should not tonify, for tonification would leave Zheng Qi unsupported and allow Xie Qi to flourish, effectively lending weapons to bandits and grain to thieves. Therefore, in treating excess conditions, one must directly remove the Xie Qi; once removed, the body is at peace. The method must be precise and focused to achieve rapid results. This is the method for treating excess. Ultimately, those who can withstand attack are excess conditions; those who cannot are deficiency conditions. False deficiency conditions are rare, while false excess conditions are most common; false cold conditions are not difficult to treat, but false heat conditions are often mistreated. I dare not lightly endorse those in the world who claim to know medicine without understanding the root and branches of truth and falsity.