热为火之用，火为热之体，故言火则不言热，言热则不言火，一而二，二而一也。温者，热之不甚者也。六气言火
不言温，举一以概二也。曰温热者，乃温病热病之总称。邪之轻者为温，邪之重者为热。近世概以温病括之，而温病乃
赅热暑湿燥而言。温病暑病之冬伤于寒而春夏发者，及春夏感邪而秋冬发者，皆谓之伏气；随时感受而即发者，谓之新
感。新感其邪轻，治之尚易；伏气其邪重，治之较难。故治温病之法不独异于伤寒，伏气与新感亦不可同日而论也。
瘟疫本名疠疫，传染病也。《素问·刺法论》云∶帝曰∶余闻五疫之至，皆相染易，无问大小，病状相似。《六元正
纪大论》云∶厉（《韵会》∶疠通作厉）大至，民善暴死。皆言疠疫之证状者也。《说文》∶疠者，恶疾也；疫者，民皆疾
也。从 役省声。《释名》∶疫，役也。言有鬼行役也。《刺法论》于疠疫之分，则以干支推之，谓天运化疫，地运化疠。
盖以疫之与疠，不过上下刚柔之异。故又以金木水火土统之，即所谓五疫者也。而按之实际，则疠疫均有寒温之别。其
流行者，温疠温疫多，而寒疠寒疫少。《六元正纪大论》曰∶其病温疠大行，远近咸若。又曰∶其病温疠。皆言温疠，
而不及寒疠，盖以温疠概寒疠也。《老子》曰∶凶年之后，必有温疫。《抱朴子》曰∶经温疫，则不畏。俱言温疫，而不
及寒疫，亦以温疫概寒疫也。后人又立杂疫之名，以统疫病之杂症也。
夫温病与瘟疫，病源既殊，治法各异，古人分辨，本极明了，不可以混同也。后人犹恐其相混，故改温疫之温作瘟。
吴又可不明此意，以古无瘟字，反混温病瘟疫为一病。（吴又可云∶《伤寒论》曰发热而渴，不恶寒者为温病；后人去
加为瘟，即瘟也。要之，古无瘟字，乃后人之自为变易者，不可因易其文，以温瘟为两病）不识温病者，以温为病名
也；温疫温疠者，以疫疠为病名，言疫之温者、疠之温者也。惟其古无瘟字，乃知瘟疫温疠之温非病名，何得反混温病
为疠疫哉？
夫言事物者，必通权而达变，医病亦何独不然？春温夏热秋凉冬寒，感之而病者，常也；《素问》曰重阴必阳，重
阳必阴，冬伤于寒，春必病温，春伤于风，夏生飧泄，夏伤于暑，秋必 疟，秋伤于湿，冬生咳嗽者，皆伏气也，则谓
之变。然犹不传染，仍属变中之常。若夫喉痧、白喉、霍乱、伏阴症、痧症、痢疾、疫痉、鼠疫，诸传染病，则又变中
之非常者也。（但白喉、霍乱、痧症、痢疾，亦有非传染而病者，则亦属变中之常）故论温病而欲穷其原委，则非明乎
常变之道不可。
然自吴又可混温病瘟疫为一之后，附和者众，而常变之理不明，治瘟疫之书多混温病，治温病之书亦杂瘟疫，后之
学人，苟非好学深思之士，鲜不为其所惑者。（松如）窃忧之，爰将关于温病瘟疫之书分别评论，俾后之读者知所取舍
焉。
热是火的作用，火是热的本体，所以说言火时不言热，言热时不言火，这是一与二的关系，二也是一的关系。温，是指热度不强烈的状态。在六气（风、寒、暑、湿、燥、火）的理论中只提火而不提温，是以“火”来概括两者。称为“温热”，是对温病和热病的总称。邪气轻浅的称为温，邪气深重的称为热。近代人通常用“温病”来统称所有此类疾病，而这里的温病实际上涵盖了热、暑、湿、燥等病因。
冬季感受寒邪而在春夏季发作的温病、暑病，以及春夏季感受邪气而在秋冬季发作的疾病，都称为伏气（潜伏之邪）；随时感受邪气随即发病的，称为新感（即时发作）。新感的邪气较轻，治疗相对容易；伏气的邪气较重，治疗较为困难。因此，治疗温病的方法不仅不同于伤寒，伏气与新感也不可同日而语。
瘟疫本名疠疫，即传染病。《素问·刺法论》说：黄帝问道：我听说五疫之气到来时，都会相互传染，无论年龄大小，病症表现相似。《素问·六元正纪大论》说：厉气（《韵会》注：疠通作厉）盛大来临时，百姓容易突然死亡。这些都是描述疠疫症状的记载。《说文解字》解释：疠，是恶疾；疫，是百姓都患的病。字形从役省声。《释名》解释：疫，通役。说是鬼魂在服役奔走。《刺法论》对于疠和疫的区别，则是通过天干地支来推演，认为天运化生疫，地运化生疠。大概是因为疫与疠的区别，不过是上下刚柔的不同。所以又用金木水火土五行来统摄它们，这就是所谓的五疫。但考察实际情况，疠疫都有寒性和温性的区别。其中流行较多的，是温疠、温疫，而寒疠、寒疫较少。《六元正纪大论》说：其病为温疠大规模流行，远近地区都一样。又说：其病为温疠。都是指温疠，而未提及寒疠，大概是用温疠来概括寒疠。《老子》说：凶年之后，必定会有温疫。《抱朴子》说：经过温疫之地，则无所畏惧。都是只提温疫而不提寒疫，也是以温疫概括寒疫。后人又设立了“杂疫”的名称，用来统括疫病中的复杂症候。
温病与瘟疫，既然病源不同，治法各异，古人分辨得非常清楚，不可以混淆。后人恐怕人们混淆，所以将“温疫”的“温”改为“瘟”。吴又可不明白这个意思，因为古代没有“瘟”字，反而将温病和瘟疫混为一谈。（吴又可说：《伤寒论》中说发热而口渴，不恶寒的是温病；后人去掉偏旁加为瘟，就是瘟。总之，古代没有瘟字，是后人自己改变文字造成的，不能因为文字的改变，就把温、瘟当作两种病）不了解温病的人，把“温”当作病名；温疫、温疠的人，把“疫疠”当作病名，意思是说属于温性的疫、属于温性的疠。正因为古代没有“瘟”字，才知道瘟疫、温疠中的“温”不是病名，怎么能反过来把温病混同为疠疫呢？
谈论事物，必须通晓权变之道，治病又何尝不是如此？春温、夏热、秋凉、冬寒，因感受这些气候而生病，是常理；《素问》说重阴必转化为阳，重阳必转化为阴，冬季感受寒邪，春季必定发生温病，春季感受风邪，夏季产生飧泄（完谷不化的腹泻），夏季感受暑邪，秋季必定发生疟疾，秋季感受湿邪，冬季产生咳嗽，这些都属伏气，称之为“变”。然而这些还不具有传染性，仍属于变化中的常态。至于喉痧、白喉、霍乱、伏阴症、痧症、痢疾、疫痉、鼠疫等各种传染病，则是变化中的非常态。（但白喉、霍乱、痧症、痢疾，也有非传染性而患病的情况，那也属于变化中的常态）所以论述温病想要穷尽其原委，就必须明白常与变的道理。
然而自从吴又可混淆温病与瘟疫为一体后，附和者众多，导致常变的道理不明，治疗瘟疫的书籍多混杂温病内容，治疗温病的书籍也夹杂瘟疫内容，后来的学人，如果不是好学深思之士，很少不被他们迷惑的。（松如）对此深感忧虑，于是将关于温病和瘟疫的书籍分别进行评论，使后来的读者知道如何取舍。
Heat is the function of Fire, and Fire is the substance of Heat. Therefore, when speaking of Fire, one does not speak of Heat; when speaking of Heat, one does not speak of Fire. They are one yet two, and two yet one. "Warmth" (Wen) refers to a state where heat is not intense. In the theory of the Six Qi (Wind, Cold, Summer-heat, Dampness, Dryness, Fire), only Fire is mentioned, not Warmth, using "Fire" to encompass both. The term "Warmth-Heat" (Wen-Re) is a general designation for Warm Diseases (Wenbing) and Heat Diseases. When the pathogenic factor is mild, it is called Warmth; when severe, it is called Heat. In modern times, "Warm Disease" is generally used as an umbrella term, which actually encompasses etiologies such as Heat, Summer-heat, Dampness, and Dryness.
Warm diseases and Summer-heat diseases caused by Winter Cold injury manifesting in Spring or Summer, as well as diseases contracted in Spring or Summer but manifesting in Autumn or Winter, are all referred to as Latent Pathogens (Fuqi). Those that manifest immediately upon contraction are referred to as New Contractions (Xingan). New contractions involve milder pathogens and are relatively easier to treat; latent pathogens involve heavier pathogens and are more difficult to treat. Therefore, the methods for treating Warm Diseases differ not only from those for Cold Damage (Shanghan), but Latent Pathogens and New Contractions cannot be compared on the same level.
Plague (Piyi) was originally named Liyi, referring to infectious diseases. *Suwen: Cifa Lun* states: The Yellow Emperor asked: I have heard that when the Five Plagues arrive, they are all contagious, regardless of age, and the symptoms are similar. *Suwen: Liuyuan Zhengji Dalun* states: When the Malignant Qi (Li) arrives in force, the people are prone to sudden death. These texts describe the symptoms of Liyi. *Shuowen Jiezi* explains: Li is a malignant disease; Yi is a disease affecting the common people. The character derives from the phonetic component of Yi (service). *Shiming* explains: Yi is synonymous with Yi (service/役). It implies ghosts performing service. In *Cifa Lun*, the distinction between Li and Yi is deduced through Heavenly Stems and Earthly Branches, stating that Heaven generates Yi, and Earth generates Li. This suggests that the difference between Yi and Li lies merely in the upper/lower and rigid/flexible aspects. Thus, they are categorized under the Five Elements (Metal, Wood, Water, Fire, Earth), known as the Five Plagues. However, in actual practice, both Li and Yi have Cold and Warm varieties. Among them, Warm Li and Warm Yi are more prevalent, while Cold Li and Cold Yi are less common. *Liuyuan Zhengji Dalun* states: Their illness is Warm Li, spreading widely, affecting distant and near areas alike. It also states: Their illness is Warm Li. These references mention Warm Li without mentioning Cold Li, likely using Warm Li to generalize Cold Li. *Laozi* states: After a year of disaster, there will inevitably be Warm Plague. *Baopuzi* states: One who has passed through a Warm Plague area fears nothing. Both texts mention Warm Plague without Cold Plague, again using Warm Plague to generalize Cold Plague. Later generations established the term "Miscellaneous Plague" (Zayi) to categorize complex syndromes within epidemics.
Since the etiology and treatment methods for Warm Diseases and Plagues are distinct, ancient scholars distinguished them clearly, and they should not be confused. Fearing confusion, later generations changed the character "Wen" (Warm) in "Wenyi" (Warm Plague) to "Wen" (Plague/Wen). Wu Youke failed to understand this meaning. Noting the absence of the character "Wen" (Plague) in ancient texts, he erroneously conflated Warm Diseases and Plagues into a single entity. (Wu Youke stated: *Shanghan Lun* says that fever with thirst and no aversion to cold constitutes a Warm Disease; later generations added the radical to create 'Wen', which is Plague. Essentially, the character 'Wen' did not exist in antiquity; it was a later alteration. One should not treat 'Wen' and 'Wen' as two different diseases based on this textual change.) Those who do not understand Warm Diseases view "Wen" as the disease name itself. For Warm Plague and Warm Li, "Yi/Li" is the disease name, specifying that it is the Warm type of Plague or Li. Precisely because the character "Wen" (Plague) did not exist in ancient times, we know that the "Wen" in Wenyi and Wenli is not a disease name. How can one then erroneously conflate Warm Disease with Liyi?
When discussing matters, one must understand flexibility and adaptation; medicine is no exception. Illnesses resulting from contracting Spring Warmth, Summer Heat, Autumn Coolness, or Winter Cold are considered normal (Chang). *Suwen* states: Extreme Yin transforms into Yang; extreme Yang transforms into Yin. Winter Cold injury leading to Spring Warm Disease, Spring Wind injury leading to Summer Sundry Diarrhea (Sunxie), Summer Heat injury leading to Autumn Malaria, and Autumn Dampness injury leading to Winter Cough are all examples of Latent Pathogens, termed "Variation" (Bian). However, these are still non-contagious and belong to the "normal within variation." Conversely, infectious diseases such as Throat Sha (Housha), White Throat (Baihou), Cholera (Huoluan), Hidden Yin Syndrome (Fuyinzheng), Sha Syndrome (Shazheng), Dysentery (Liji), Epidemic Spasm (Yijing), and Bubonic Plague (Shuyi) represent the "abnormal within variation." (Note: Baihou, Huoluan, Shazheng, and Liji can also occur non-infectiously, in which case they fall under the "normal within variation.") Therefore, to thoroughly investigate the origins and details of Warm Diseases, one must comprehend the principles of Normalcy and Variation.
However, since Wu Youke conflated Warm Diseases and Plagues, many have followed suit, obscuring the principles of Normalcy and Variation. Books on treating Plagues often mix in Warm Disease content, and books on treating Warm Diseases often include Plague content. Subsequent scholars, unless they are diligent and deep thinkers, are rarely unaffected by this confusion. (Songru) deeply worries about this and has therefore critically reviewed books concerning Warm Diseases and Plagues separately, enabling future readers to make informed choices.