所以谓伤寒、热病有别者，别于诊不别于症，别于法不别于药。气盛身寒，得之伤寒；
气虚
身热，得之伤暑。诊之别也。然而伤寒传变，则亦身热；伤暑发狂，则亦气盛。非症之无别
者
乎？浅人误认，职是故耳！伤寒皆先汗后下；温热或先下后汗∶法之别也。然而汗则麻、葛，
下则硝、黄；伤寒之汗、下以是，温热之汗、下亦以是。非药之无别者乎？由是推之，伤寒
虽因于寒，一经化热，舍黄连、石膏，更用何药以凉之？温热虽已为热，倘或过治，舍干姜
、附子，更用何药以温之？人生之患，纵有万端，本草之数，止此一定，药可通用，方何独
不可通用？近之解《伤寒论》者，执其中之白虎、黄芩等汤，以证此书之兼出温热治法。彼
将谓伤寒病始终不宜寒药，温热病始终不宜温药乎？噫！医可若是之固哉？
寒之为气，虽截然与热对峙，而其伤人也，则随人虚实而为病。其人实，则寒不能深入
，但
着于皮肤，而闭其腠理，即不得不热；其人虚，则寒无所隔碍，遂过乎肌表而达于脏腑，即
不得不寒。苟取《素》风论之旨绎之，即知仲景方论寒热杂见之故矣。若《素》热论人伤于
寒，则为病热云云，乃专主寒邪在经之常法，以答篇首六七日之问，不兼直中言，与仲景为
寒字尽致者义别。河间泥此，遂谓伤寒有热无寒，概指通脉、理中等症，为得之寒药误下，
非惟浓诬仲景，并误会《内经》也。寒之乘也，猛于他气，故例曰∶其伤于四时之气，皆能
为病。以伤寒为毒者，以其最成杀厉之气也。河间乃谓温热凉寒，皆取伤寒而分其微甚，是
以伤寒为四气病统称，岂其然乎？寒之藏也，历春至夏，则阳气大泄，而不能复留，故例止
云寒毒藏于肌骨，至春变为温病，至夏变为暑病。河间乃续之曰∶秋变为湿病，冬变为正伤
寒。如此任意增改，其不足与语伤寒也明矣。
所以说，认为伤寒与热病是有区别的，这种区别在于诊断方法的不同，而不在于症状的不同；在于治疗法则的不同，而不在于药物的不同。气机亢盛而身体发冷，这是感受了伤寒；气机虚弱而身体发热，这是感受了伤暑。这是诊断上的区别。然而，伤寒在传变过程中，也会出现身体发热；伤暑严重时出现狂躁，也会出现气机亢盛的现象。这难道不是症状上没有区别吗？浅薄的人错误地认识这一点，就是由于这个原因啊！
治疗伤寒通常先使用汗法，后使用下法；治疗温热病有时先使用下法，后使用汗法：这是治疗法则的区别。然而，发汗常用麻黄、葛根，攻下常用芒硝、大黄；伤寒的汗法和下法使用这些药物，温热病的汗法和下法也使用这些药物。这难道不是药物上没有区别吗？由此推论，伤寒虽然是因为寒邪引起，但一经化热，除了黄连、石膏，还能用什么药来清热呢？温热病虽然已经是热证，但如果治疗过度损伤阳气，除了干姜、附子，还能用什么药来温补呢？人生的疾病，纵然有万种端绪，但本草所载的药物数量是有限的，药物可以通用，方剂为什么唯独不能通用呢？
近来解读《伤寒论》的人，执着于书中提到的白虎汤、黄芩汤等方剂，以此来证明这本书兼有治疗温热病的方法。他们难道会认为伤寒病始终不宜用寒凉药，温热病始终不宜用温热药吗？唉！医生怎么能如此固执不通呢？
寒邪之气，虽然截然与热邪相对峙，但它伤人时，却是随着人体虚实的情况而发病。如果人体正气充实，那么寒邪就不能深入，只是附着在皮肤，闭塞腠理，这就不得不表现为发热；如果人体正气虚弱，那么寒邪就没有阻隔阻碍，于是越过肌表直达脏腑，这就不得不表现为寒冷。如果取《素问·风论》的宗旨来推究，就知道张仲景的方论中寒热症状杂见的原因了。至于《素问·热论》中说“人伤于寒，则为病热”等等，那是专门针对寒邪在经络这一常规情况的说法，用来回答篇首关于六七日病程的问题，并不兼指直中脏腑的情况，这与张仲景将“寒”字含义发挥到极致的义理是不同的。
刘河间拘泥于这一点，于是认为伤寒只有热没有寒，一概将通脉四逆汤、理中汤等病症，归结为误用寒凉药攻下所致，这不仅严重诬蔑了张仲景，也误解了《内经》。寒邪侵袭，猛烈胜过其他邪气，所以医经例言说：“人伤于四时之气，皆能为病。”之所以称伤寒为毒，是因为它形成了最具有杀伤厉气的邪气。刘河间却认为温热、凉、寒，都是取法伤寒并区分其轻重程度，这是把伤寒作为四时邪气的统称，难道真是这样吗？
寒邪潜伏，经历春天到夏天，阳气大量宣泄，而不能重新留存，所以医经例言只说寒毒潜伏于肌骨，到了春天变为温病，到了夏天变为暑病。刘河间却接着补充说：秋天变为湿病，冬天变为正伤寒。像这样任意增改，他不足以与他谈论伤寒的道理是显而易见的。
Therefore, it is said that the distinction between Shanghan (Cold Damage) and Rebing (Heat Disease) lies in the difference of diagnosis, not symptoms; in the difference of treatment principles, not herbs. When Qi is abundant but the body feels cold, this results from contracting Shanghan; when Qi is deficient but the body feels hot, this results from contracting Shangs (Summerheat). This constitutes the distinction in diagnosis. However, during the transmission of Shanghan, the body may also become hot; when Shangs leads to mania, Qi may also become abundant. Is this not an indication that there is no distinction in symptoms? Superficial practitioners misunderstand this, precisely due to this reason!
The treatment for Shanghan typically employs sweating methods first, followed by purgative methods; whereas the treatment for Wenre (Warm-Heat) diseases may employ purgative methods first, followed by sweating methods: this constitutes the distinction in treatment principles. However, sweating often utilizes Ephedrae Herba (Mahuang, 麻黄) and Puerariae Radix (Gegen, 葛根); purgation often utilizes Mirabilite (Xiashaofen, 硝) and Rhubarb (Dahuang, 大黄). The sweating and purgative treatments for Shanghan use these, and the sweating and purgative treatments for Wenre also use these. Is this not an indication that there is no distinction in herbs? From this we can infer: although Shanghan originates from Cold pathogen, once it transforms into Heat, apart from Coptidis Rhizoma (Huanglian, 黄连) and Gypsum Fibrosum (Shigao, 石膏), what other herbs can be used to cool it? Although Wenre disease is already a Heat condition, if treated excessively leading to Yang deficiency, apart from Zingiberis Radix Preparata (Ganjiang, 干姜) and Aconiti Lateralis Radix Preparata (Fuzi, 附子), what other herbs can be used to warm it? Human ailments, though myriad in nature, are limited by the fixed number of herbs in Materia Medica. If herbs can be used universally, why should formulas not be used universally?
Recent commentators on the *Treatise on Cold Damage* (*Shanghan Lun*) cling to formulas such as Baihu Tang (White Tiger Decoction) and Huangqin Tang (Scutellaria Decoction) found within the text, using them to prove that this book encompasses treatment methods for Warm-Heat diseases. Would they claim that Shanghan disease should never use Cold herbs throughout its course, and that Warm-Heat disease should never use Warm herbs throughout its course? Alas! Can physicians be so rigid and inflexible?
The Qi of Cold, although distinctly opposed to Heat, affects humans according to their constitution's excess or deficiency. If a person is Excess (Shi), Cold cannot penetrate deeply; it merely attaches to the skin and closes the Couli (pores), inevitably resulting in Heat manifestation. If a person is Deficient (Xu), Cold encounters no obstruction, passes through the muscle layer, and reaches the Zang-Fu organs, inevitably resulting in Cold manifestation. If one expounds upon the principles of the *Suwen: Fenglun* (Wind Chapter of the Basic Questions), one will understand the reason why Zhang Zhongjing’s formula discussions present mixed Cold and Heat symptoms.
The statement in *Suwen: Relun* (Heat Chapter of the Basic Questions) that "when humans are injured by Cold, they develop Heat diseases," etc., specifically addresses the standard method of Cold pathogen residing in the meridians, answering the question posed at the beginning of the chapter regarding the six-to-seven-day progression. It does not include direct invasion (Zhizhong) into the interior, which differs in meaning from Zhang Zhongjing’s exhaustive elaboration on the concept of "Cold." Liu Hejian, adhering rigidly to this view, asserted that Shanghan involves only Heat and no Cold, attributing conditions treated with Tongmai Sini Tang (Pulse-Recovering Decoction) and Lizhong Tang (Regulate the Middle Decoction) solely to errors caused by mistaken purgation with Cold herbs. This not only severely slandered Zhang Zhongjing but also misinterpreted the *Neijing*.
Cold attacks more fiercely than other pathogens; hence, the general principle states: "Injury by the Qi of the four seasons can all cause disease." Shanghan is termed "poison" because it forms the most lethal and destructive Qi. Liu Hejian, however, argued that Warm, Heat, Cool, and Cold are all derived from Shanghan, differentiated only by degree, thereby treating Shanghan as a collective term for diseases caused by the four seasonal pathogens. Is this really the case?
Cold hides within the body. Passing through Spring to Summer, Yang Qi is greatly depleted and cannot remain stored. Therefore, the general principle states only that Cold poison hides in the muscles and bones, transforming into Wenbing (Warm Diseases) in Spring and Shubing (Summerheat Diseases) in Summer. Liu Hejian added: transforming into Shibing (Dampness Diseases) in Autumn, and Zhengshanghan (True Shanghan) in Winter. Such arbitrary alteration makes it clear that he is unworthy of discussing the principles of Shanghan.