伤寒之病，莫先于分表里；治表里之法，莫先于分汗、下。汗、下一差，变症百出，是以前人论治伤寒，有曰汗药
宜早，下药宜迟。此二语虽云大纲，亦紧要法也。然曰宜早者，谓风寒之邪自表而入，即当速为发表，即仲景所谓觉病
须臾，即宜早治，不避晨夜是也。其曰宜迟者，谓风寒之邪传入于里，攻下必须在正阳阳明之腑，即仲景所谓下早恐成
痞气与结胸是也。此云“迟早”，论治法非论时刻也。而《此事难知》谓非预早之早，乃早晚之早，发汗当在午前阳分；
非待久之迟，攻下当在巳后阴分。以迟、早二字，作日候之迟、早解，惑乱人心为甚，宜亟正之。
伤寒六经传变，自表入里，三阳为表，三阴为里，自浅而深，六经传尽，必无出而再传之理。成氏
以六日厥阴传经已尽，七日当愈；七日不愈，再自太阳传出，复至厥阴；十三日不愈，谓之过经坏病。此
等注释，谬戾殊甚。马元台辨之，谓太阳至厥阴，犹人入户升堂以入于室。太阳为三阳，最在外；阳明为
二阳，在太阳之内；少阳为一阳，在阳明之内。此三阳之在表也。太阴为三阴，在少阳之内；少阴为二
阴，在太阴之内；厥阴为一阴，在少阴之内。此三阴之里也。故一日始于太阳，二日传阳明，三日传少
阳，四日传太阴，五日传少阴，六日传厥阴。经文之论次第相传，亦言其大概耳！所云七日不愈再传经
者，七日行经未尽，仍在太阳一经故也。如仲景所谓太阳病头痛，七日以上自愈，以行其经尽也，若欲再
作经者，针足阳明，使经不传则愈。可见太阳一经有行之七日以上者，则阳明、少阳亦可羁留过经不解。
故针阳明中土，使经不传，此行其经未尽，未尝曰传其经尽也。若云六经传尽，复自厥阴出，而再传太
阳，则有二阴、三阴、一阳、二阳以格之，容有自外入内，又自内而越于外之理？风寒之邪，入人脏腑，
岂两阴交尽于里，复从皮毛外而再入太阳以为害者耶？成氏之谬，千古大惑，请从辨之。
伤寒病的治疗，没有比区分表证和里证更优先的了；治疗表证和里证的方法，没有比区分发汗法和攻下法更优先的了。发汗与攻下只要出现一次差错，就会引发上百种变证，因此前人论述治疗伤寒时，曾说“发汗药宜早用，攻下药宜迟用”。这两句话虽然说是总纲，也是至关重要的法则。
所谓“宜早”，是指风寒之邪从体表侵入，就应当迅速发散表邪，这正是张仲景所说的“发觉病情须臾之间，就应当尽早治疗，不分早晚”的意思。所谓“宜迟”，是指风寒之邪传入体内，攻下必须在正气充盛的阳明腑实证时才进行，这正是张仲景所说的“过早攻下恐怕会形成痞气或结胸证”的意思。这里说的“迟早”，讨论的是治法的时机原则，而非具体的钟点时刻。
然而，《此事难知》一书认为，这里的“早”不是指预先提前的早，而是指一天中早晨的早，发汗应当在午前阳气旺盛的时候进行；这里的“迟”不是指等待很久的迟，攻下应当在巳时之后阴气初生时进行。将“迟、早”二字解释为日期的先后，极大地迷惑人心，应当立即予以纠正。
伤寒六经的传变，是从表入里，三阳经属表，三阴经属里，由浅入深，六经传遍之后，必然没有再向外传变的道理。成无己认为，经过六天厥阴经传变已尽，第七天应当痊愈；如果第七天未愈，则再次从太阳经传出，重新传至厥阴经；如果十三天未愈，称为过经坏病。这些注释谬误极其严重。马元台对此进行了辨析，认为从太阳经到厥阴经，就像人进入门户、登上厅堂然后进入内室一样。太阳经是三阳，在最外面；阳明经是二阳，在太阳经之内；少阳经是一阳，在阳明经之内。这三阳经位于体表。太阴经是三阴，在少阳经之内；少阴经是二阴，在太阴经之内；厥阴经是一阴，在少阴经之内。这三阴经位于体内。所以第一天始于太阳经，第二天传至阳明经，第三天传至少阳经，第四天传至太阴经，第五天传至少阴经，第六天传至厥阴经。经文关于次第相传的论述，也只是说个大概罢了！所说的“七日不愈再传经”，是因为七天内行经未尽，病邪仍在太阳一经的缘故。正如张仲景所说：“太阳病头痛，七天以上自愈，是因为行经已尽。”如果打算让它再传一经，针刺足阳明经，使病邪不传变就能痊愈。由此可见，太阳一经有运行七天以上的情况，那么阳明经、少阳经也可能滞留超过经期而不解。所以针刺阳明中土（脾胃），使病邪不传变，这是说行经未尽，并没有说传经已尽。如果说六经传遍之后，又从厥阴经出来，再传回太阳经，那么有二阴、三阴、一阳、二阳作为阻隔，怎么会有从外入内，又直接从内部越出到体外的道理呢？风寒之邪侵入人体脏腑，难道会在两阴交尽于里的情况下，又从皮毛外部再次侵入太阳经来造成危害吗？成无己的错误，是千古以来的大迷惑，请允许我加以辨正。
In the treatment of Cold Damage (Shanghan) disease, nothing is more primary than distinguishing between Exterior (Biao) and Interior (Li) patterns; in treating Exterior and Interior patterns, nothing is more primary than distinguishing between Sweating (Han) and Purging (Xia) methods. A single error in sweating or purging can lead to hundreds of complications; therefore, predecessors discussing the treatment of Cold Damage stated that "Sweating herbs should be used early, and Purging herbs should be used late." Although these two phrases serve as a general principle, they are also crucial therapeutic rules.
The phrase "should be used early" refers to the fact that when Wind-Cold pathogens enter from the exterior, one should promptly release the Exterior pathogen. This aligns with Zhang Zhongjing's saying: "Once the disease is perceived, even for an instant, it should be treated early, regardless of morning or night." The phrase "should be used late" refers to the principle that when Wind-Cold pathogens have transmitted into the Interior, purging must only be performed when there is excess heat in the Yang Ming Fu organs (Stomach and Intestines). This aligns with Zhang Zhongjing's warning: "Purging too early may lead to Pi Qi (Glomus/Epigastric fullness) or Jie Xiong (Chest Binding)." Here, "early and late" discuss the principles of therapeutic timing, not specific clock hours.
However, the book *Ci Shi Nan Zhi* (Difficulties of Certain Matters) argues that this "early" does not mean preemptive early, but rather the "morning" of the day, suggesting that sweating should occur before noon during the Yang phase; and this "late" does not mean waiting for a long time, but suggests that purging should occur after the Si hour (9-11 AM) during the Yin phase. Interpreting the characters "late" and "early" as referring to the sequence of days causes great confusion among people and must be urgently corrected.
The transmission of the Six Channels (Liu Jing) in Cold Damage proceeds from the Exterior to the Interior. The Three Yang channels belong to the Exterior, and the Three Yin channels belong to the Interior, progressing from shallow to deep. Once the Six Channels have been fully transmitted through, there is no logical possibility of further transmission outward. Cheng Wuji claimed that after six days, the transmission through the Jue Yin channel is complete, and healing should occur on the seventh day; if not healed by the seventh day, it transmits again starting from the Tai Yang channel, repeating until reaching Jue Yin; if not healed by the thirteenth day, it is termed "Guo Jing Huai Bing" (Disease beyond the period with deterioration). These annotations are extremely erroneous. Ma Yuantai refuted this, stating that transmission from Tai Yang to Jue Yin is like entering a house, ascending to the hall, and then entering the inner room. Tai Yang is the First Yang, located furthest outward; Yang Ming is the Second Yang, inside Tai Yang; Shao Yang is the Third Yang, inside Yang Ming. These Three Yang channels are at the Exterior. Tai Yin is the First Yin, inside Shao Yang; Shao Yin is the Second Yin, inside Tai Yin; Jue Yin is the Third Yin, inside Shao Yin. These Three Yin channels are at the Interior. Thus, on the first day, the disease begins in Tai Yang; on the second day, it transmits to Yang Ming; on the third day, to Shao Yang; on the fourth day, to Tai Yin; on the fifth day, to Shao Yin; and on the sixth day, to Jue Yin. The canonical text's discussion of sequential transmission merely outlines the general trend. The statement about "transmitting again if not healed by the seventh day" implies that within seven days, the course of transmission was incomplete, and the pathogen remained solely in the Tai Yang channel. As Zhang Zhongjing stated: "Tai Yang disease with headache heals spontaneously after seven days because the course of the channel has been completed." If one wishes for it to transmit to another channel, needling the Foot Yang Ming channel can prevent transmission and result in cure. This demonstrates that Tai Yang can persist for more than seven days; similarly, Yang Ming and Shao Yang may also linger beyond their periods without resolving. Therefore, needling the Earth element of Yang Ming (Spleen/Stomach) prevents transmission, indicating that the course of transmission was incomplete, not that the transmission cycle had finished. If one claims that after the Six Channels are fully transmitted, the pathogen exits from Jue Yin and re-transmits to Tai Yang, it would have to pass through barriers of Two Yin, Three Yin, One Yang, and Two Yang. How could there be a logic where the pathogen enters from outside to inside, and then directly jumps out to the exterior? When Wind-Cold pathogens invade the Zang-Fu organs, how could they, having reached the depth of the Two Yin channels, return from the skin and hair to invade Tai Yang again to cause harm? Cheng Wuji's error represents a profound misunderstanding throughout history, which I shall now clarify.