汉长沙着《伤寒论》，以治风、寒、暑、湿、燥、火六气之邪，非仅为寒邪而设。然则其书名伤寒何
也？盖缘十二经脉，惟足太阳在表，为寒水之经，凡六淫之邪为病者，皆必先伤于寒水之经，故曰伤寒。
今人都以寒水之寒字，误为寒热之寒，若此则伤寒之书，专治寒邪，而风、暑、燥、湿、火，了不干涉矣。
殊不思长沙首列桂枝汤以治风，明明指人统治六气，而非仅治一寒邪之意，于此已露一斑。若果专治寒邪，
理当列麻黄汤、附子汤、四逆、理中等汤为先，而不列桂枝汤为首也。况又有白虎汤以治暑，五苓散以治湿，
炙甘草汤以治燥，大小承气以治火，此显明六气统治之书，而今以为专治寒邪，则误甚矣。时贤又谓伤寒论六
经，温热论三焦，此两句书，更为印定眼目。不知邪气袭人，皆由表而入于里，惟温疫之气，秽浊之气，乃论
三焦可也。以其气从口鼻而入，先扰于上，次传中下，除此而外，则风、寒、暑、湿、燥、火，无不尽从表
入。况李 谓“太阳行身之表，外邪皆得伤之”。其伤寒之书，能统治六气者，可无疑矣。凡学治时病者，
必须读仲景《伤寒论》，参读时贤之书，考古酌今，则胸中自有风、寒、暑、湿、燥、火之界限。若不
读仲景之本，而专读时贤之书，真所谓舍本求末矣。
In the Han Dynasty, Zhang Zhongjing, the Grand Administrator of Changsha, authored *Shanghan Lun* (Treatise on Cold Damage Diseases) to treat pathogens of the six qi (Six Climatic Factors: Wind, Cold, Summer-heat, Dampness, Dryness, and Fire), not merely for the purpose of treating Cold pathogen. Then why is the book named *Shanghan Lun*? It is because among the twelve meridians, only the Foot-Taiyang Bladder Meridian is located at the exterior and belongs to the Water-Cold meridian. Whenever diseases are caused by the six excesses (Liuyin, the six climatic factors acting as pathogens), they invariably first injure the Water-Cold meridian; hence it is called "Shanghan" (Cold Damage).
Modern people mistakenly interpret the character "Han" (Cold) in "Water-Cold" as referring to "Cold-Heat" differentiation. If this interpretation were correct, then *Shanghan Lun* would exclusively treat Cold pathogen, having no relevance to Wind, Summer-heat, Dryness, Dampness, or Fire. Little do they realize that Zhang Zhongjing listed Guizhi Tang (Cinnamon Twig Decoction) first to treat Wind, clearly indicating that the book governs the treatment of all six qi, rather than just a single Cold pathogen. This is evident from the very beginning. If it truly treated only Cold pathogen, logic would dictate listing Mahuang Tang (Ephedra Decoction), Fuzi Tang (Aconite Decoction), Sini Tang (Frigid Extremities Decoction), and Lizhong Tang (Regulate the Middle Decoction) as primary formulas, rather than placing Guizhi Tang first. Moreover, the text includes Baihu Tang (White Tiger Decoction) to treat Summer-heat, Wuling San (Five-Ling Powder) to treat Dampness, Zhigancao Tang (Honey-Fried Licorice Decoction) to treat Dryness, and Dachengqi Tang (Major Order the Qi Decoction) and Xiaochengqi Tang (Minor Order the Qi Decoction) to treat Fire. This explicitly demonstrates that it is a book governing the treatment of the six qi. To regard it now as exclusively treating Cold pathogen is a significant error.
Contemporary scholars further assert that *Shanghan Lun* discusses the Six Meridians (Liu Jing), while *Wenre Lun* (Treatise on Warm Heat) discusses the Triple Burner (San Jiao). These two statements have further confined scholarly perspective. One should understand that pathogens invading the human body enter from the exterior into the interior. Only the Qi of Warm Epidemics (Wenyi) and turbid/filthy Qi are appropriately discussed via the Triple Burner differentiation, as these pathogens enter through the mouth and nose, first disturbing the Upper Burner, then transmitting to the Middle and Lower Burners. Apart from these, Wind, Cold, Summer-heat, Dampness, Dryness, and Fire all enter from the exterior. Furthermore, Li Shizhen stated, "The Taiyang meridian runs along the exterior of the body, and external pathogens can all injure it." Thus, there is no doubt that his *Shanghan Lun* can govern the treatment of the six qi.
Those who study and treat seasonal diseases must read Zhang Zhongjing's *Shanghan Lun* and reference the works of contemporary experts. By examining ancient texts and considering modern practices, one will naturally discern the boundaries between Wind, Cold, Summer-heat, Dampness, Dryness, and Fire. If one does not read Zhang Zhongjing's foundational classic but instead specializes only in the works of contemporary experts, it is truly described as abandoning the root to pursue the branches.