少阳主三阳中之半表半里，少阳之腑属胆与三焦。又因少阳主火化，故以“口苦，咽干，目眩”为少阳病提纲。其病机为枢机不利，正邪分争，少阳受病，进而影响脾胃不和之故。少阳主要病证，当与“往来寒热，胸胁苦满，默默不欲饮食，心烦，喜呕”等互参。
三阴病属阴中之里。太阴病重点在脾，主寒湿之化。脾虚脏寒，故太阴病以“腹满而吐，食不下，自利益甚，时腹自痛”等为主证。太阴脏寒，累及下焦肾命真阳，往往形成少阴寒化证。
少阴病重点在心肾，以“脉微细，但欲寐”为提纲。少阴病分阳虚寒化与阴虚热化两大证型；阳虚寒化证有脉微细，但欲寐，恶寒卧或厥冷，下利或呕逆等；阴虚热化证，则有脉细数，舌质绛，咽干咽痛，心烦不得眠等。
厥阴病重点在肝。厥阴病以“消渴，气上撞心，心中疼热，饥而不欲食，食则吐蛔。下之，利不止”为提纲。此是厥阴上热下寒，寒热错杂之证。但厥阴病又有寒证、热证、厥热胜复证及厥、利、呕、哕四大证型。
此外，三阳三阴病中，还可出现合病并病和病邪不自表而径入于里之三阴直中之证。
以上皆以六病立论———即三阳三阴之为病是也，何谓中医之无病乎？第三卷１７６盖三阳三阴之病，又不是固定不变的，而是发病之后，其病机可以相互影响，并且可以转化的。今以太阳表病为例：如病势轻浅，可以自愈；亦有病候始终稽留于表而持久不愈；有阳盛传入阳明之腑或转为少阳病的；有阴盛传入少阴之脏或转为太阴或厥阴病的；更有转为结胸、痞证等而属杂病范畴的。又以少阴里病为例：有阳回而自愈者；有兼表寒而反发热者；有纯阴无阳而成危重之证；有阴盛阳衰而为格阳、戴阳者；有阴竭阳越而成不治之证等等。盖病之传变与否，多与病邪的盛衰，正气的强弱，宿疾的有无以及误治与否等有关。如正胜邪衰，虽是三阴病可以逐渐向愈；若邪盛正衰，则三阳病也可趋向严重。故必须随时根据病证变化的情况，细致审辨，方为得之。
然辨病必须审证，而审辨证候在《伤寒论》中，尤为具体而细致准确。何谓证？如“脉浮，头项强痛而恶寒”，发热为太阳病。在太阳病脉证的基础上，若“或已发热，或未发热，必恶寒，体痛、呃逆，脉阴阳俱紧者，名为伤寒”。见无汗而喘，为麻黄汤证；若不汗出而烦躁，则是表寒里热，为大青龙证；见无汗而干呕咳喘，为表寒里饮，是小青龙证；若无汗而项背强，则是表为寒束，经俞不利，即葛根汤证。又如“太阳病，发热汗出，恶风，脉缓者，名为中风”，病机为营卫不和，卫强营弱，即桂枝汤证；见脉浮或脉浮数，发热汗出，少腹里急，烦渴或渴欲饮水，水入即吐，小便不利，为太阳蓄水，有表里证，即五苓散证等等。
阳明病以身热，汗自出，不恶寒，反恶热，脉洪大等为主要脉证。如见大烦渴不解，为气分大热，即白虎或白虎加人参汤证。若兼腹满痛，不大便，潮热，谵语等，为腑实燥结之证。腑实燥结，其证偏于心烦、谵语、蒸蒸发热者，为里热偏盛，是调胃承气证；偏于“腹大满不通”者，为浊气结滞，是小承气证；若邪热与宿垢结为燥屎，腹满痛不解，或痞满燥实坚数症俱备，则是大承气证。
少阳病以往来寒热，胸胁苦满，默默不欲饮食，心烦喜呕，口苦，咽干，目眩，舌苔白，脉弦等为主要脉证，亦即小柴胡证。兼表证有发热，微恶寒，肢节烦疼，心下支结者，为柴胡桂枝证；兼里实有潮热，不大便或下利属热结旁流者，为柴胡加芒硝汤证；兼呕不止，心下急，郁郁微烦，则是大柴胡证；兼水饮内结，证见胸胁满微结，小便不利，渴而不呕，往来寒热，心烦者，则是柴胡桂枝干姜汤证；兼胸满，烦惊，谵语，小便不利，一身尽重不可转侧者，是病邪弥漫于表里之间，寒热相混，虚实夹杂，为柴胡加龙牡汤证。
太阴病以腹满而吐，食不下，自利益甚，时腹自痛，不渴，脉弱等为主要脉证，实际即理中证。若里证已和，见脉浮可汗，则是太阴表证。如里证严重，累及少阴肾命真阳，下利厥冷，又是四逆汤证。
少阴病分阳虚寒化与阴虚热化两大证型：阳虚而寒的主要脉证有脉微细，但欲寐，恶寒卧或厥冷，下利或呕逆等。若少阴兼表，无里证，反发热，脉沉者，是麻附细辛甘草汤证；又少阴无热，背恶寒，身体痛，手足寒，骨节痛，脉沉，是阳虚而寒，即附子汤证；若少阴病，小便不利，腹痛，四肢沉重疼痛，自下利，是阳虚水泛，即真武证；又大汗大下而厥冷者，为四逆证；更有阴盛于内，阳扰于外，出现有下利清谷，脉微欲绝，身反不恶寒，其人面色赤者，名格阳，即通脉四逆证。有少阴病脉微下利，面赤，为阴盛于下，阳浮于上，下真寒而上假热，名戴阳，即白通汤证。
若利不止，厥逆，无脉，干呕心烦者，是白通加猪胆汁汤证。至于少阴阴虚而热的主要证型，一般有脉细数，舌质绛，心中烦不得眠，咽干咽痛等。如少阴病，心中烦，不得眠，是真阴亏虚，心火内扰，即黄连阿胶汤证。少阴下利，咽痛，胸满，心烦，是利下伤阴，为猪肤汤证。若下利咳而第三卷１７７呕渴，心烦不得眠，小便不利，是少阴阴虚而水热相结，即猪苓汤证等。
厥阴病，消渴，气上撞心，心中疼热，饥而不欲食，食则吐蛔，下利者是厥阴寒热夹杂、上热下寒之证。有先见厥利，后见发热者，为厥热胜复之证。厥阴病寒证，如手足厥寒，脉细欲绝之寒厥，为当归四逆汤证。又有热证，如热利下重，渴欲饮水，是白头翁汤证。
六经病中，主证之外，又有兼证。如太阳桂枝证，有兼项背强，兼微喘，兼阳虚漏汗者。少阳小柴胡证，有兼渴，兼腹痛，兼心下悸，小便不利者。此外，在六经病的过程中，往往出现属于杂病范畴之证候者，如结胸、痞证、悬饮等是。
审证又须辨病，尤为《伤寒论》之主要特色，亦是仲景“见病知源”的关键所在，与后世见证治证，头痛医头者大有不同。举例言之，如下利一证，从形象看，当属于肠，与太阴阳明有关。
但从六经衡之，三阳三阴之病，都可导致下利。如“太阳与阳明合病，必自下利，葛根汤主之。”此云两阳合病，其病机实因表病而影响肠胃升降失司，引起下利。故治法重在解表，是表病下利也。若“太阳病，桂枝证，医反下之，利遂不止，脉促者，表未解也；喘而汗出者，葛根黄芩黄连汤主之。”“太阳与少阳合病，自下利者，与黄芩汤。”以上二者，一见于太阳葛根证后，是表里俱热之下利；一称太阳少阳合病，是里热下利。实则都与阳明有关。又“下利，谵语者，有燥屎也，宜小承气汤。”“阳明少阳合病，必下利。……脉滑而数者，有宿食也，当下之，宜大承气汤。”下利一证，使用下法，似属通因通用。但其下利实为热结旁流一类，虽流者似流，而结者自结，故当审结实的程度，而定用下法的轻重。然阳热亢盛，阴液潜耗，如“少阴病，自利清水，色纯青，心下必痛，口干燥者，急下之，宜大承气汤。”虽见下利，亦应采取急下存阴一法，但仍有里实证在，此义又须明确。若“伤寒发热，汗出不解，心中痞硬，呕吐而下利者，大柴胡汤主之。”病属少阳而兼里实下利，故治宜和解通下并用之法。至于三阴虚寒，最易出现下利。如“自利不渴者，属太阴，以其藏有寒故也，当温之，宜服四逆辈。”是太阳藏寒下利。”“大汗，若大下利而厥冷者，四逆汤主之。”是少阴阳衰下利。“伤寒先厥后发热，下利必自止。”是厥阴厥热胜复之下利。其少阴病真武、白通、通脉四逆等方，厥阴病寒热错杂上热下寒之证，如乌梅丸、干姜芩连人参汤等，都以下利为主证。此外，如“少阴病，下利，便脓血者，桃花汤主之。”“热利，下重者，白头翁汤主之。”二者虽云下利，实则重在便脓血，但前者属少阴寒利，后者属厥阴热利，不容相紊。
综上所述，是知仲景诊治疾病的中心思想，既重在辨病，又强调辨证，如此对于正确诊断患者邪正的盛衰，阴阳的变化，表里的出入，病势的轻重缓急，以决定治疗措施和相适应的方药，是有重要实践意义的。
３辨六经证治异同《伤寒论》六经病中，审其异同，实属辨证施治的重要关键。同一类型的疾病，有因发病原因、病理机制不同，或各个病证在其发展阶段的具体不同，而不能采用同一的治法。不同类型的疾病，因其发病主因、病理机制相同，或处于某一阶段的性质相同，又可施用同一的治法。但疾病证候复杂、治法多样，故异同之辨，应当辩证看待。今就同中求异、异中有同及异中求同、同中有异两点，试为论述于次：（１）同中求异、异中有同：六经病中，既有各个不同的类型病证，又有各个不同的治疗方法，故必须辨析其同中之异。例如太阳病以脉浮，头项强痛而恶寒为主脉主证。若发热汗出恶风脉缓者，名为中风，即桂枝证；若或以发热，或未发热，必恶寒、体痛、呕逆、无汗而喘，脉阴阳俱紧，名为伤寒，即麻黄汤证。是二者同为太阳表病，而有中风、伤寒之分矣。阳明病以身大热，第三卷１７８汗自出，不恶寒，反恶热，脉洪大为主脉主证。若见烦渴，是气分热证，为经证；若见潮热，谵语，腹满硬痛，大便不通，脉沉实，苔黄燥，为燥实热结，属腑证。是二者同为阳明里热之病，而有经腑之辨矣。少阳病以往为寒热，胸胁苦满，默默不欲饮食，心烦喜呕，口苦咽干，目眩，舌苔白，脉弦细为主脉主证，兼里实则有潮热或呕不止，心下急，郁郁微烦；兼水饮不化，则有胸胁满微结，小便不利，渴而不呕，但头汗出，兼发热微恶寒等则为表未解之证。至于三阴，如太阴病以腹满而吐，食不下，自利益甚，时腹自痛为主证。兼表亦有发热恶寒等证。少阴病以脉微细，但欲寐为主脉主证，如兼背恶寒，身体痛，手足寒，骨节痛，口中和，脉沉，为少阴阳虚无热恶寒之证；兼腹痛，小便不利，四肢沉重疼痛，下利，是阳虚水泛之证。若病从始得之，有反发热，无汗，脉沉，则是兼有表证。更有病势危重，证见四肢厥逆，下利清谷，或脉微欲绝，身反不恶寒，面色赤等，则是少阴阳虚阴盛之寒厥，或为真寒假热之格阳、戴阳之证。厥阴病因原文叙证较杂，尚无明显例子可资佐证，故从略。
从同中求异，又反复推究其异中有同，则对于六经辨证论治之基本精神，更进一步有所认识。上举太阳病中风伤寒两证，伤寒用麻黄汤开泄腠理，解表发汗。方中麻桂并用，辛温宣发之义显然。若桂枝汤解肌祛风，调和营卫，以治太阳中风，似不宜列为汗剂。但此方服后以“遍身似有汗者益佳”。所谓“脉浮数者，可发汗，宜桂枝汤。”（５７条）“脉浮者，可发汗，宜桂枝汤。”（２７６条）则桂枝汤仍属汗法，当无疑义。推之温病列于太阳表病，治法与伤寒中风自有辛凉、辛温之异。惟因势利导，使邪从外泄，亦当属于汗法范畴。《内经》谓“其在皮者，汗而发之”是也。阳明病主方如白虎汤辛甘寒法以清解气分大热，三承气汤苦咸寒法，以通下腑实燥结。
然阳明病以燥热为主，治法重点针对阳明邪热，虽有通下有形燥结与清解无形气热之分，但均属于“热者寒之”之治法。少阳病在半表半里，枢机不利。病不在表，则不可汗，又不在里，是不可下，故治法以和解为主。因病又有兼表兼里或兼水饮不化之别，故方有柴胡桂枝汤，大柴胡汤，柴胡加芒硝汤，柴胡桂枝干姜汤等之异。但柴胡类方，均从小柴胡汤增损变化而来，可以领会其重点仍具和法之意。太阴病属脏寒，法当温中，主方如理中丸。如偏于里虚，脾肾阳微，则补火燠土，所谓“宜四逆辈”。如兼表证，则宜表里双解，方如桂枝人参汤。但立法中心大意总以温里为主。少阴病寒化各证，因病程有新久，感邪有微甚，正气受损之程度有轻重不同，故或用麻附细辛甘草汤以温阳解表，或用附子汤温阳补虚，或以四逆汤回阳救逆等等不同。但因同属于少阴阳虚，治法重点仍在于温里扶阳方面。以上二者亦即“寒者热之”的治法。
少阳经主管三阳经中处于半表半里的阶段，少阳的腑属于胆和三焦。又因为少阳主司火气的转化，所以以“口苦、咽干、目眩”作为少阳病的提纲证。其病机在于枢机运转不利，正气与邪气相互争持，导致少阳受病，进而影响脾胃功能不和。少阳的主要病证，应当结合“寒热往来、胸胁部苦于胀满、沉默寡言不想进食、心烦、喜欢呕吐”等症状来综合参考。
三阴病属于阴经中的里证。太阴病的重点在脾脏，主要主司寒湿的转化。由于脾虚且内脏寒冷，所以太阴病以“腹部胀满并呕吐、无法进食、腹泻逐渐加重、时常腹部自痛”等为主要症状。太阴脏腑寒冷，累及下焦肾和命门的真阳，往往形成少阴寒化证。
少阴病的重点在心肾，以“脉象微细、只想睡觉（精神萎靡）”作为提纲证。少阴病分为阳虚寒化和阴虚热化两大证型；阳虚寒化证有脉象微细、只想睡觉、怕冷蜷卧或四肢厥冷、腹泻或呕吐逆气等症状；阴虚热化证，则有脉象细数、舌质深红、咽喉干燥疼痛、心烦不能入睡等症状。
厥阴病的重点在肝脏。厥阴病以“口渴多饮、气向上冲撞心脏、心中疼痛且有灼热感、饥饿但不想吃东西、吃东西则吐出蛔虫、如果误用泻下法，会导致腹泻不止”作为提纲证。这是厥阴上热下寒、寒热错杂的证候。但厥阴病又有寒证、热证、厥热胜复证以及厥、利、呕、哕四大证型。
此外，在三阳和三阴病中，还可能出现合病、并病，以及病邪不经过体表而直接侵入三阴经的“直中”证候。
以上都是以六经病立论——即三阳三阴所导致的疾病，那么为什么说中医没有固定的病名呢？第三卷176页提到：三阳三阴的疾病，并不是固定不变的，而是发病之后，其病机可以相互影响，并且可以发生转化。现在以太阳表病为例：如果病势轻浅，可以自愈；也有病候始终停留在体表而持久不愈的；有阳气旺盛传入阳明腑或转为少阳病的；有阴气旺盛传入少阴脏或转为太阴或厥阴病的；更有转为结胸、痞证等属于杂病范畴的。又以少阴里病为例：有阳气回复而自愈的；有兼有表寒反而发热的；有纯阴无阳而成危重证的；有阴盛阳衰而导致格阳、戴阳的；有阴液枯竭阳气外越而成不治之证的等等。大概疾病的传变与否，多与病邪的盛衰、正气的强弱、是否有宿疾以及是否误治等因素有关。如果正气战胜邪气衰退，即使是三阴病也可以逐渐向愈；如果邪气强盛正气衰弱，那么三阳病也可趋向严重。所以必须随时根据病证变化的情况，细致审辨，才算得当。
然而，辨别疾病必须审查证候，而在《伤寒论》中，审查辨证候尤为具体、细致和准确。什么是证？例如“脉浮、头项强痛且怕冷”，发热即为太阳病。在太阳病脉证的基础上，如果“或者已经发热，或者尚未发热，必定怕冷、身体疼痛、呃逆、脉阴阳俱紧的”，名为伤寒”。见到无汗且气喘，是麻黄汤证；如果不汗出且烦躁，则是表寒里热，是大青龙汤证；见到无汗且干呕咳嗽气喘，是表寒里饮，是小青龙汤证；如果无汗且项背强直，则是体表被寒邪束缚，经络俞穴不利，即葛根汤证。又如“太阳病，发热汗出、怕风、脉缓的”，名为中风”，病机为营卫不和，卫气强而营气弱，即桂枝汤证；见到脉浮或脉浮数、发热汗出、小腹拘急、烦渴或想喝水、水入即吐、小便不利，为太阳蓄水证，有表里同病，即五苓散证等等。
阳明病以身热、自然出汗、不怕冷反而怕热、脉洪大等主要脉证为特征。如见极度烦渴不解，为气分大热，即白虎汤或白虎加人参汤证。如果兼有腹部胀满疼痛、不大便、潮热、谵语等，为腑实燥结的证候。腑实燥结，其证偏于心烦、谵语、蒸蒸发热者，为里热偏盛，是调胃承气汤证；偏于“腹部大满不通”者，为浊气结滞，是小承气汤证；如果邪热与宿食糟粕结为燥屎，腹部胀满疼痛不解，或者痞、满、燥、实、坚、数等症状俱全，则是大承气汤证。
少阳病以寒热往来、胸胁部苦于胀满、沉默寡言不想进食、心烦喜欢呕吐、口苦、咽干、目眩、舌苔白、脉弦等主要脉证为特征，也就是小柴胡汤证。兼有表证有发热、轻微怕冷、肢节烦疼、心下部支撑结聚的，为柴胡桂枝汤证；兼有里实有潮热、不大便或腹泻属于热结旁流者，为柴胡加芒硝汤证；兼有呕吐不止、心下部急迫、郁郁微烦，则是大柴胡汤证；兼有水饮内结，证见胸胁满闷微结、小便不利、口渴但不呕吐、寒热往来、心烦者，则是柴胡桂枝干姜汤证；兼有胸满、惊悸、谵语、小便不利、全身沉重不可转侧者，是病邪弥漫于表里之间，寒热相混，虚实夹杂，为柴胡加龙牡汤证。
太阴病以腹部胀满并呕吐、无法进食、腹泻逐渐加重、时常腹部自痛、口不渴、脉弱等主要脉证为特征，实际上就是理中汤证。如果里证已调和，见到脉浮可发汗，则是太阴表证。如果里证严重，累及少阴肾和命门的真阳，出现腹泻和四肢厥冷，又是四逆汤证。
少阴病分为阳虚寒化和阴虚热化两大证型：阳虚而寒的主要脉证有脉象微细、只想睡觉、怕冷蜷卧或四肢厥冷、腹泻或呕吐逆气等。如果少阴兼有表证，没有里证，反而发热，脉沉的，是麻黄附子细辛甘草汤证；又如果少阴无热，背部怕冷，身体疼痛，手脚寒冷，骨节疼痛，脉沉，是阳虚而寒，即附子汤证；如果少阴病，小便不利、腹痛、四肢沉重疼痛、自行腹泻，是阳虚水泛，即真武汤证；又如果大汗大下后出现四肢厥冷的，为四逆汤证；更有阴盛于内，阳气扰动于外，出现腹泻完谷不化、脉微欲绝、身体反而不怕冷、其人面色赤红的，名为格阳，即通脉四逆汤证。有少阴病脉微腹泻、面赤，为阴盛于下，阳气浮于上，下真寒而上假热，名为戴阳，即白通汤证。
如果腹泻不止、四肢厥逆、无脉、干呕心烦的，是白通加猪胆汁汤证。至于少阴阴虚而热的主要证型，一般常有脉象细数、舌质深红、心中烦闷不能入睡、咽喉干燥疼痛等。如少阴病，心中烦闷、不能入睡，是真阴亏虚、心火内扰，即黄连阿胶汤证。少阴腹泻、咽喉痛、胸满、心烦，是腹泻伤阴，为猪肤汤证。如果腹泻咳嗽且呕吐口渴、心烦不能入睡、小便不利，是少阴阴虚而水热互结，即猪苓汤证等。
厥阴病，口渴多饮、气向上冲撞心脏、心中疼痛且有灼热感、饥饿但不想吃东西、吃东西则吐出蛔虫、腹泻的是厥阴寒热夹杂、上热下寒的证候。有先见四肢厥冷腹泻，后见发热的，为厥热胜复的证候。厥阴病的寒证，如手足厥寒、脉细欲绝的寒厥，为当归四逆汤证。又有热证，如热性腹泻伴肛门重坠、想喝水，是白头翁汤证。
六经病中，在主证之外，又有兼证。如太阳桂枝汤证，有兼项背强直、兼轻微气喘、兼阳虚漏汗的。少阳小柴胡汤证，有兼口渴、兼腹痛、兼心下悸动、小便不利的。此外，在六经病的过程中，往往出现属于杂病范畴的证候，如结胸、痞证、悬饮等。
审查证候又必须辨别疾病，这尤为《伤寒论》的主要特色，也是张仲景“见病知源”的关键所在，与后世只见症状治疗症状、头痛医头的做法大有不同。举例来说，如下利一证，从形象看，当属于肠道，与太阴、阳明有关。
但从六经衡量，三阳三阴的疾病，都可以导致下利。如“太阳与阳明合病，必定自发性腹泻，用葛根汤主治。”这里说两阳合病，其病机实际是因为表病影响了肠胃升降功能的失调，引起下利。所以治法重在解表，这是表病引起的下利。如果“太阳病，桂枝汤证，医生反而用泻下法，腹泻于是不止，脉急促的，说明表邪未解；气喘且出汗的，用葛根黄芩黄连汤主治。”“太阳与少阳合病，自发性腹泻的，给予黄芩汤。”以上二者，一见之于太阳葛根汤证后，是表里俱热的下利；一称太阳少阳合病，是里热下利。实则都与阳明有关。又“腹泻，伴有谵语的，有燥屎存在，宜用小承气汤。”“阳明少阳合病，必定腹泻。……脉滑而数的，有宿食存在，应当用下法，宜用大承气汤。”下利一证，使用下法，似乎属于通因通用的治法。但其下利实为热结旁流一类，虽然流出的看似正常，但内部的结滞依然存在，所以应当审辨结实的程度，来决定使用下法的轻重。然而阳热亢盛，阴液暗中消耗，如“少阴病，自行腹泻清水，颜色纯青，心下部必定疼痛，口干燥的，紧急用下法，宜用大承气汤。”虽然见到下利，也应当采取急下存阴的一法，但这仍有里实证存在，这一义理又须明确。如果“伤寒发热，汗出而病不解，心下部痞硬，呕吐且腹泻的，用大柴胡汤主治。”病属少阳而兼有里实下利，所以治宜和解与通下并用之法。至于三阴虚寒，最易出现下利。如“自行腹泻且不口渴的，属于太阴，因为其内脏有寒的缘故，应当温补，宜服用四逆汤类方剂。”这是太阴脏寒下利。“大汗，或者大腹泻且四肢厥冷的，用四逆汤主治。”这是少阴阳衰下利。“伤寒先四肢厥冷后发热，腹泻必定自行停止。”这是厥阴厥热胜复之下的下利。其少阴病的真武汤、白通汤、通脉四逆汤等方，厥阴病寒热错杂上热下寒的证候，如乌梅丸、干姜芩连人参汤等，都以下利为主证。此外，如“少阴病，腹泻，大便带脓血的，用桃花汤主治。”“热利，肛门重坠的，用白头翁汤主治。”二者虽云下利，实则重在便脓血，但前者属少阴寒利，后者属厥阴热利，不容混淆。
综上所述，可知张仲景诊治疾病的核心思想，既重在辨别疾病，又强调辨证施治，如此对于正确诊断患者邪正的盛衰、阴阳的变化、表里的出入、病势的轻重缓急，以决定治疗措施和相适应的方药，具有重要的实践意义。
3. 辨析六经证治的异同：《伤寒论》六经病中，审察其异同，实属辨证施治的重要关键。同一类型的疾病，有因发病原因、病理机制不同，或各个病证在其发展阶段的具体不同，而不能采用同一的治法。不同类型的疾病，因其发病主因、病理机制相同，或处于某一阶段的性质相同，又可施用同一的治法。但疾病证候复杂、治法多样，故对异同的辨析，应当辩证看待。现就同中求异、异中有同及异中求同、同中有异两点，试为论述如下：（1）同中求异、异中有同：六经病中，既有各个不同的类型病证，又有各个不同的治疗方法，故必须辨析其同中之异。例如太阳病以脉浮、头项强痛且怕冷为主脉主证。如果发热汗出恶风脉缓的，名为中风，即桂枝汤证；如果或以发热，或未发热，必定怕冷、身体疼痛、呕吐逆气、无汗且气喘，脉阴阳俱紧的，名为伤寒，即麻黄汤证。是二者同为太阳表病，而有中风、伤寒之分了。阳明病以身大热、自然出汗、不怕冷反而怕热、脉洪大为主脉主证。如果见烦渴，是气分热证，为经证；如果见潮热、谵语、腹部胀满硬痛、大便不通、脉沉实、苔黄燥，为燥实热结，属腑证。是二者同为阳明里热之病，而有经腑之辨了。少阳病以寒热往来、胸胁苦满、沉默寡言不想进食、心烦喜呕、口苦咽干、目眩、舌苔白、脉弦细为主脉主证，兼里实则有潮热或呕吐不止、心下部急迫、郁郁微烦；兼水饮不化，则有胸胁满闷微结、小便不利、口渴但不呕吐、仅头部出汗、兼发热轻微怕冷等则为表未解之证。至于三阴，如太阴病以腹部胀满并呕吐、无法进食、腹泻逐渐加重、时常腹部自痛为主证。兼表亦有发热恶寒等证。少阴病以脉微细、只想睡觉为主脉主证，如兼背部怕冷、身体疼痛、手脚寒冷、骨节疼痛、口中平和、脉沉，为少阴阳虚无热恶寒之证；兼腹痛、小便不利、四肢沉重疼痛、腹泻，是阳虚水泛之证。如果病从开始就有反常发热、无汗、脉沉，则是兼有表证。更有病势危重，证见四肢厥逆、腹泻完谷不化、或脉微欲绝、身体反而不怕冷、面色赤红等，则是少阴阳虚阴盛之寒厥，或为真寒假热之格阳、戴阳之证。厥阴病因原文叙述证候较杂乱，尚无明显例子可资佐证，故从略。
从同中求异，又反复推究其异中有同，则对于六经辨证论治的基本精神，更进一步有所认识。上举太阳病中风伤寒两证，伤寒用麻黄汤开泄腠理，解表发汗。方中麻黄、桂枝并用，辛温宣发的含义显然。若桂枝汤解肌祛风，调和营卫，以治太阳中风，似乎不宜列为发汗剂。但此方服后以“遍身微微似有汗出的为佳”。所谓“脉浮数的，可发汗，宜用桂枝汤。”（第57条）“脉浮的，可发汗，宜用桂枝汤。”（第276条）则桂枝汤仍属汗法，当无疑义。推之温病列于太阳表病，治法与伤寒中风自有辛凉、辛温之异。惟因势利导，使邪气从外部排泄，也当属于汗法范畴。《内经》谓“病在皮表的，用发汗法发散”即是此意。阳明病主方如白虎汤用辛甘寒法以清解气分大热，三承气汤用苦咸寒法，以通下腑实燥结。
然而阳明病以燥热为主，治法重点针对阳明邪热，虽有通下有形燥结与清解无形气热之分，但均属于“热者寒之”的治法。少阳病在半表半里，枢机不利。病不在表，则不可发汗，又不在里，是不可泻下，故治法以和解为主。因病又有兼表兼里或兼水饮不化的区别，故方有柴胡桂枝汤、大柴胡汤、柴胡加芒硝汤、柴胡桂枝干姜汤等的差异。但柴胡类方，均从小柴胡汤增损变化而来，可以领会其重点仍具和法之意。太阴病属脏寒，法当温中，主方如理中丸。如偏于里虚，脾肾阳微，则补火燠土，所谓“宜用四逆汤类方剂”。如兼有表证，则宜表里双解，方如桂枝人参汤。但立法中心大意总以温里为主。少阴病寒化各证，因病程有新久，感邪有微甚，正气受损的程度有轻重不同，故或用麻黄附子细辛甘草汤以温阳解表，或用附子汤温阳补虚，或以四逆汤回阳救逆等不同。但因同属于少阴阳虚，治法重点仍在于温里扶阳方面。以上二者亦即“寒者热之”的治法。
Shaoyang (Lesser Yang) governs the half-exterior and half-interior stage among the three Yang meridians, and its fu organs belong to the Gallbladder and Sanjiao (Triple Burner). Furthermore, because Shaoyang is primarily associated with the transformation of Fire, "bitter taste in the mouth, dry throat, and dizziness" serve as the guiding symptoms for Shaoyang disease. Its pathogenesis involves the dysfunction of the pivot mechanism, a struggle between healthy qi and pathogenic factors, leading to Shaoyang involvement, which subsequently affects the harmonious functioning of the Spleen and Stomach. The main manifestations of Shaoyang disease should be comprehensively considered alongside symptoms such as "alternating chills and fever, bitter fullness in the chest and hypochondrium, silence with loss of appetite, mental irritability, and frequent vomiting."
The Three Yin diseases belong to the interior aspect of the Yin meridians. Taiyin (Greater Yin) disease focuses on the Spleen and is primarily governed by the transformation of Cold-Dampness. Due to Spleen deficiency and internal cold, the main symptoms of Taiyin disease include "abdominal fullness with vomiting, inability to eat, worsening spontaneous diarrhea, and occasional spontaneous abdominal pain." When Taiyin organ cold affects the true Yang of the Kidney and Mingmen (Gate of Life) in the lower Jiao, it often forms the Shaoyin Cold-Transformation syndrome.
Shaoyin (Lesser Yin) disease focuses on the Heart and Kidneys, with "faint and thin pulse, and a desire only to sleep (listlessness)" serving as the guiding symptoms. Shaoyin disease is divided into two major syndromes: Yang-deficiency Cold-Transformation and Yin-deficiency Heat-Transformation. The Yang-deficiency Cold-Transformation syndrome presents with faint and thin pulse, listlessness, aversion to cold with a desire to curl up or cold limbs, diarrhea, or vomiting and regurgitation. The Yin-deficiency Heat-Transformation syndrome presents with fine and rapid pulse, crimson tongue body, dry and painful throat, and mental irritability with insomnia.
Jueyin (Terminal Yin) disease focuses on the Liver. Its guiding symptoms are "excessive thirst, sensation of Qi rushing up to strike the heart, pain and heat sensation in the epigastrium, hunger without desire to eat, vomiting roundworms after eating, and if purgatives are misused, unceasing diarrhea." This represents a syndrome of upper Heat and lower Cold, with mixed Cold and Heat. However, Jueyin disease also includes Cold syndromes, Heat syndromes, Jue-Reversal and Heat-Alternation syndromes, and four major types: Jue-reversal, Diarrhea, Vomiting, and Hiccups.
Additionally, within the Three Yang and Three Yin diseases, combined diseases (Hebing), concurrent diseases (Bingbing), and direct invasion of the Three Yin meridians by pathogens bypassing the exterior (Zhizhong) may occur.
The above discussions are based on the theory of Six Meridian diseases—that is, diseases arising from the Three Yang and Three Yin. So, why is it said that Traditional Chinese Medicine does not have fixed disease entities? Volume 3, p. 176 states: Diseases of the Three Yang and Three Yin are not fixed; rather, after onset, their pathogenesis can influence each other and transform. Taking Taiyang (Greater Yang) exterior disease as an example: if the pathological process is mild, it may resolve spontaneously; some cases remain stuck at the exterior persistently; some transform due to excess Yang entering the Yangming Fu organs or becoming Shaoyang disease; some transform due to excess Yin entering the Shaoyin Zang organs or becoming Taiyin or Jueyin disease; others transform into conditions like Chest Binding (Jie Xiong) or Epigastric Fullness (Pi Zheng), falling into the category of miscellaneous diseases. Taking Shaoyin interior disease as another example: some resolve spontaneously upon the return of Yang; some present with fever despite having exterior Cold; some become critical due to pure Yin without Yang; some develop Ge-Yang (blocking Yang) or Dai-Yang (floating Yang) due to Yin excess and Yang decline; some become untreatable due to exhaustion of Yin and floating of Yang. Generally, whether a disease transmits depends on the strength of the pathogen versus healthy qi, the presence of chronic conditions, and whether mis-treatment occurred. If healthy qi overcomes the declining pathogen, even Three Yin diseases may gradually heal; if the pathogen is strong and healthy qi weak, even Three Yang diseases may worsen. Therefore, one must carefully differentiate based on the changing condition at all times to achieve proper treatment.
However, differentiating disease requires examining syndromes (Zheng), and in *Shanghan Lun* (Treatise on Cold Damage), this examination is particularly specific, detailed, and accurate. What constitutes a syndrome? For instance, "floating pulse, stiffness and pain in the head and neck, and aversion to cold," accompanied by fever, indicates Taiyang disease. On the basis of Taiyang pulse and syndrome, if there is "either already fever or no fever yet, but definitely aversion to cold, body pain, hiccups, and a pulse that is tight at both yin and yang positions," it is named Cold Damage (Shanghan). Seeing no sweat and wheezing indicates Mahuang Tang (Ephedra Decoction) syndrome; seeing no sweat but restlessness indicates exterior Cold and interior Heat, corresponding to Da Qing Long Tang (Major Blue-Green Dragon Decoction) syndrome; seeing no sweat, dry retching, cough, and wheezing indicates exterior Cold and interior Fluid retention, corresponding to Xiao Qing Long Tang (Minor Blue-Green Dragon Decoction) syndrome; seeing no sweat and stiffness in the nape and back indicates exterior constraint by Cold and dysfunction of the collaterals, corresponding to Gegen Tang (Kudzu Decoction) syndrome. Again, "Taiyang disease with fever, sweating, aversion to wind, and a slow pulse" is named Wind Strike (Zhong Feng), with a pathogenesis of disharmony between Ying (Nutritive) and Wei (Defensive) qi, where Wei is strong and Ying is weak, corresponding to Guizhi Tang (Cinnamon Twig Decoction) syndrome; seeing floating or floating-rapid pulse, fever, sweating, urgency in the lower abdomen, irritability/thirst or desire to drink water with immediate vomiting upon drinking, and difficult urination indicates Taiyang Water Accumulation with simultaneous exterior-interior involvement, corresponding to Wuling San (Five-Ling Powder) syndrome.
Yangming (Bright Yang) disease is characterized mainly by high fever, spontaneous sweating, absence of aversion to cold but presence of aversion to heat, and a large (Hongda) pulse. If extreme irritability and unquenchable thirst are seen, it indicates intense Heat in the Qi level, corresponding to Baihu Tang (White Tiger Decoction) or Baihu Jia Renshen Tang (White Tiger Plus Ginseng Decoction) syndrome. If accompanied by abdominal fullness and pain, constipation, tidal fever, and delirium, it indicates Fu-organ Excess with Dryness-Firmness accumulation. Within Fu-excess Dryness-Firmness, if symptoms lean towards irritability, delirium, and steaming fever, it indicates predominant interior Heat, corresponding to Tiaowei Chengqi Tang (Regulate the Stomach and Purge Qi Decoction) syndrome; if leaning towards "severe abdominal fullness and obstruction," it indicates stagnation of turbid Qi, corresponding to Xiaochengqi Tang (Minor Purge Qi Decoction) syndrome; if pathogenic Heat combines with retained feces to form dry stool, with unremitting abdominal fullness and pain, or if all symptoms of Pi (stuffy), Man (full), Zao (dry), Shi (excess), Jian (hard), and Shu (frequent) are present, it corresponds to Dachengqi Tang (Major Purge Qi Decoction) syndrome.
Shaoyang disease is characterized mainly by alternating chills and fever, bitter fullness in the chest and hypochondrium, silence with loss of appetite, mental irritability and frequent vomiting, bitter taste in the mouth, dry throat, dizziness, white tongue coating, and wiry pulse, which is essentially the Xiaochaihu Tang (Minor Bupleurum Decoction) syndrome. If accompanied by exterior symptoms such as fever, slight aversion to cold, joint pain, and subcostal binding, it is Chaihu Guizhi Tang (Bupleurum and Cinnamon Twig Decoction) syndrome; if accompanied by interior excess such as tidal fever, constipation, or diarrhea belonging to Heat-binding with peripheral flow, it is Chaihu Jia Mangxiao Tang (Bupleurum Plus Mirabilite Decoction) syndrome; if accompanied by incessant vomiting, epigastric urgency, and slight depression/irritability, it is Dachaihu Tang (Major Bupleurum Decoction) syndrome; if accompanied by internal fluid retention presenting with slight chest/hypochondriac fullness-knotting, difficult urination, thirst without vomiting, alternating chills and fever, and irritability, it is Chaihu Guizhi Ganjiang Tang (Bupleurum, Cinnamon Twig, and Dried Ginger Decoction) syndrome; if accompanied by chest fullness, fright/delirium, delirium, difficult urination, and whole-body heaviness preventing turning, it indicates pathogen diffusing between exterior and interior, mixing Cold and Heat, and mixing Deficiency and Excess, corresponding to Chaihu Jia Longgu Muli Tang (Bupleurum Plus Dragon Bone and Oyster Shell Decoction) syndrome.
Taiyin disease is characterized mainly by abdominal fullness with vomiting, inability to eat, worsening spontaneous diarrhea, occasional spontaneous abdominal pain, lack of thirst, and weak pulse, which is practically Lizhong Tang (Regulate the Middle Decoction) syndrome. If the interior condition has harmonized and a floating pulse allows for sweating, it is a Taiyin exterior syndrome. If the interior condition is severe, affecting the true Yang of the Shaoyin Kidney and Mingmen, leading to diarrhea and cold limbs, it corresponds to Sini Tang (Reverse the Collapse Decoction) syndrome.
Shaoyin disease is divided into two major syndromes: Yang-deficiency Cold-Transformation and Yin-deficiency Heat-Transformation. The main pulse and syndrome features of Yang-deficiency Cold include faint and thin pulse, listlessness, aversion to cold with desire to curl up or cold limbs, diarrhea, or vomiting/regurgitation. If Shaoyin is combined with exterior syndrome, lacking interior signs but presenting with fever and deep pulse, it is Ma Huang Fu Zi Xi Xin Gan Cao Tang (Ephedra, Aconite, Asarum, and Licorice Decoction) syndrome; again, if Shaoyin lacks fever, presents with aversion to cold in the back, body pain, cold hands and feet, bone/joint pain, and deep pulse, it is Yang-deficiency Cold, corresponding to Fuzi Tang (Aconite Decoction) syndrome; if Shaoyin disease presents with difficult urination, abdominal pain, heavy/painful limbs, and spontaneous diarrhea, it is Yang-deficiency with Water Overflow, corresponding to Zhenwu Tang (True Warrior Decoction) syndrome; again, if massive sweating or purging leads to cold limbs, it is Sini Tang syndrome; furthermore, if Yin excess internally and Yang disturbance externally lead to diarrhea with undigested food, pulse barely perceptible, body actually not averse to cold, and red facial complexion, it is named Ge-Yang (Blocking Yang), corresponding to Tongmai Sini Tang (Pulse-Unblocking Reverse Collapse Decoction) syndrome. If Shaoyin disease presents with faint pulse, diarrhea, and red face, it is Yin excess below and Yang floating above, true Cold below and false Heat above, named Dai-Yang (Floating Yang), corresponding to Bitong Tang (Open the Pass Decoction) syndrome.
If diarrhea is unceasing, limbs are cold/reversed, pulse is absent, with dry retching and irritability, it is Bitong Jia Zhu Dan Ye Tang (Bitong Plus Pig Bile Decoction) syndrome. Regarding the main syndromes of Shaoyin Yin-deficiency with Heat, generally there are fine and rapid pulse, crimson tongue body, mental irritability with insomnia, and dry/painful throat. If Shaoyin disease presents with mental irritability and insomnia, it is True Yin deficiency with internal disturbance by Heart Fire, corresponding to Huanglian Ejiao Tang (Coptis and Egg Yolk Decoction) syndrome. If Shaoyin diarrhea presents with sore throat, chest fullness, and irritability, it is Yin injury from diarrhea, corresponding to Zhufu Tang (Pig Skin Decoction) syndrome. If diarrhea, cough, vomiting, thirst, mental irritability with insomnia, and difficult urination occur, it is Shaoyin Yin-deficiency with Water-Heat binding, corresponding to Zhuling Tang (Polyporus Decoction) syndrome, etc.
Jueyin disease, presenting with excessive thirst, Qi rushing to strike the heart, pain/heat in the epigastrium, hunger without desire to eat, vomiting roundworms after eating, and diarrhea, represents a Jueyin mixed Cold-Heat syndrome with upper Heat and lower Cold. If cold limbs and diarrhea appear first, followed by fever, it is a Jue-Reversal and Heat-Alternation syndrome. The Cold syndrome of Jueyin, such as cold limbs with a fine pulse nearly absent (Cold Reversal), corresponds to Danggui Sini Tang (Angelica Sinensis Pulse-Unbinding Decoction) syndrome. There is also a Heat syndrome, such as hot diarrhea with rectal tenesmus and desire to drink water, corresponding to Baitouweng Tang (Pulsatilla Decoction) syndrome.
In the Six Meridian diseases, besides main syndromes, there are combined syndromes. For example, Taiyang Guizhi Tang syndrome may combine with neck/back stiffness, slight wheezing, or Yang-deficiency with leakage of sweat. Shaoyang Xiaochaihu Tang syndrome may combine with thirst, abdominal pain, palpitations in the epigastrium, or difficult urination. Additionally, during the course of Six Meridian diseases, syndromes belonging to miscellaneous diseases often appear, such as Chest Binding, Epigastric Fullness, and Suspended Fluid.
Examining syndromes requires differentiating diseases, which is a primary feature of *Shanghan Lun* and the key to Zhang Zhongjing's principle of "seeing the disease to know its source," differing greatly from later practices of treating symptoms symptomatically ("headache, treat the head"). For example, regarding diarrhea: visually, it belongs to the Intestines and relates to Taiyin and Yangming.
However, measured by Six Meridians, diseases of the Three Yang and Three Yin can all cause diarrhea. For instance, "Taiyang and Yangming combined disease inevitably causes spontaneous diarrhea, treated with Gegen Tang." Here, combined disease of two Yangs implies the pathogenesis is actually exterior disease affecting the ascending/descending function of the Stomach and Intestines, causing diarrhea. Thus, the treatment focuses on releasing the exterior; this is exterior-induced diarrhea. If "Taiyang disease, Guizhi syndrome, treated incorrectly with purgatives, resulting in unceasing diarrhea, with an urgent pulse indicating the exterior is unresolved; if accompanied by wheezing and sweating, treated with Gegen Huangqin Huanglian Tang (Kudzu, Scutellaria, and Coptis Decoction)." "Taiyang and Shaoyang combined disease with spontaneous diarrhea is treated with Huangqin Tang (Scutellaria Decoction)." The former follows Taiyang Gegen syndrome, representing interior-exterior Heat diarrhea; the latter is Taiyang-Shaoyang combined disease, representing interior Heat diarrhea. Both essentially relate to Yangming. Also, "Diarrhea with delirium indicates dry stool, suitable for Xiaochengqi Tang." "Yangming-Shaoyang combined disease inevitably causes diarrhea... slippery and rapid pulse indicates retained food, requiring purgation, suitable for Dachengqi Tang." Using purgation for diarrhea seems to follow the principle of "treating obstruction with draining methods" (Tong Yin Tong Yong). However, this diarrhea is actually Heat-binding with peripheral flow; although the flow appears normal, the binding remains. Therefore, one must assess the degree of firmness to determine the intensity of purgation. Yet, when Yang-Heat is hyperactive and Yin fluids are secretly consumed, as in "Shaoyin disease, spontaneous diarrhea of clear green water,必 (must) have epigastric pain, and dry mouth/throat, urgently purge with Dachengqi Tang." Even with diarrhea, the method of urgent purgation to preserve Yin should be adopted, provided there is still interior excess. This principle must be clear. If "Cold damage with fever, sweating but illness unresolved, epigastric stuffiness/hardness, vomiting and diarrhea, treated with Dachaihu Tang." The disease is Shaoyang combined with interior excess diarrhea, so treatment should combine harmonizing and purging. Regarding Three Yin Deficiency-Cold, diarrhea is most likely to appear. For example, "Spontaneous diarrhea without thirst belongs to Taiyin, because the Zang organs have Cold, so warm them, suitable for Sini Tang category." This is Taiyin Zang-Cold diarrhea. "Massive sweating or massive diarrhea with cold limbs, treated with Sini Tang." This is Shaoyin Yang-depletion diarrhea. "Cold damage starting with cold limbs then fever, diarrhea will stop spontaneously." This is Jueyin Jue-Reversal/Heat-Alternation diarrhea. Other formulas for Shaoyin like Zhenwu, Bitong, Tongmai Sini, and for Jueyin mixed Cold-Heat upper-Hot lower-Cold like Wu Mei Wan (Mume Pill) and Ganjiang Qinlian Renshen Tang (Dried Ginger, Scutellaria, Coptis, and Ginseng Decoction) all take diarrhea as a main symptom. Additionally, "Shaoyin disease, diarrhea with pus and blood in stool, treated with Taohua Tang (Peach Flower Decoction)." "Hot diarrhea with rectal tenesmus, treated with Baitouweng Tang." Although both mention diarrhea, they focus on pus/blood in stool; the former is Shaoyin Cold diarrhea, the latter is Jueyin Heat diarrhea, and they must not be confused.
In summary, Zhang Zhongjing's central thought in diagnosing and treating diseases emphasizes both differentiating disease and differentiating syndromes. This has significant practical value for correctly assessing the balance of pathogenic vs. healthy qi, changes in Yin/Yang, movement between exterior/interior, and severity/urgency of the disease process, thereby determining treatment measures and appropriate formulas.
3. Differentiating Similarities and Differences in Six Meridian Treatment: In the Six Meridian diseases of *Shanghan Lun*, examining similarities and differences is crucial for syndrome differentiation and treatment. Diseases of the same type may require different treatments due to different etiologies, pathomechanisms, or specific stages. Diseases of different types may share the same treatment if their primary causes, pathomechanisms, or stage natures are identical. Given the complexity of syndromes and diversity of treatments, the differentiation of similarities and differences should be viewed dialectically. We discuss here two points: seeking differences within similarities and similarities within differences, and seeking similarities within differences and differences within similarities. (1) Seeking differences within similarities and similarities within differences: Among Six Meridian diseases, there are various syndrome types and treatment methods, so one must analyze differences within similarities. For example, Taiyang disease takes floating pulse, head/neck stiffness/pain, and aversion to cold as main pulses/syndromes. If fever, sweating, aversion to wind, and slow pulse are present, it is named Wind Strike, i.e., Guizhi Tang syndrome; if fever (or no fever), definite aversion to cold, body pain, vomiting, no sweat, wheezing, and tight pulse at yin/yang positions are present, it is named Cold Damage, i.e., Mahuang Tang syndrome. Both are Taiyang exterior diseases but differ into Wind Strike and Cold Damage. Yangming disease takes high fever, spontaneous sweating, no aversion to cold but aversion to heat, and large pulse as main features. If irritability and thirst are seen, it is Qi-level Heat syndrome, a Jing (Channel) syndrome; if tidal fever, delirium, abdominal fullness/hardness/pain, constipation, deep-solid pulse, and yellow-dry coating are seen, it is Dryness-Firmness Heat binding, a Fu (Organ) syndrome. Both are Yangming interior Heat diseases but differ into Channel and Organ syndromes. Shaoyang disease takes alternating chills/fever, chest/hypochondriac fullness, silence/loss of appetite, irritability/vomiting, bitter taste/dry throat/dizziness, white coating, and wiry-thin pulse as main features. Combined with interior excess, there is tidal fever or incessant vomiting/epigastric urgency/depression; combined with untransformed fluid retention, there is slight chest/hypochondriac knotting, difficult urination, thirst without vomiting, head-only sweating, plus slight fever/aversion to cold indicating unresolved exterior. As for the Three Yin: Taiyin disease takes abdominal fullness/vomiting, inability to eat, worsening diarrhea, occasional abdominal pain as main symptoms, possibly combined with exterior fever/aversion to cold. Shaoyin disease takes faint-thin pulse and listlessness as main features; if combined with back aversion to cold, body pain, cold limbs/joints, neutral mouth, and deep pulse, it is Shaoyin Yang-deficiency without Heat aversion to Cold; if combined with abdominal pain, difficult urination, heavy/painful limbs, and diarrhea, it is Yang-deficiency Water Overflow. If from onset there is contrary fever, no sweat, and deep pulse, it combines exterior syndrome. If critically ill with cold limbs, diarrhea with undigested food, or barely perceptible pulse, body not averse to cold, red face, it is Shaoyin Yang-deficiency Yin-excess Cold Reversal, or True Cold False Heat Ge-Yang/Dai-Yang syndromes. Jueyin disease text is complex, so examples are omitted.
By seeking differences within similarities and repeatedly exploring similarities within differences, one gains deeper insight into the basic spirit of Six Meridian syndrome differentiation and treatment. Regarding the Taiyang Wind Strike and Cold Damage examples: Cold Damage uses Mahuang Tang to open pores, release exterior, and induce sweating. The combination of Ephedra and Cinnamon Twig clearly signifies acrid-warm dispersal. Guizhi Tang releases muscle layer, dispels wind, and harmonizes Ying/Wei to treat Taiyang Wind Strike; it might seem unsuitable as a diaphoretic. However, after administration, "general slight sweating is best." As stated, "Floating-rapid pulse, can induce sweating, suitable for Guizhi Tang" (Line 57); "Floating pulse, can induce sweating, suitable for Guizhi Tang" (Line 276). Thus, Guizhi Tang belongs to the sweating method without doubt. Extending this, Warm Disease classified under Taiyang exterior has acrid-cool vs. acrid-warm differences compared to Cold Damage Wind Strike. Nevertheless, guiding the pathogen outwards belongs to the sweating method category. *Neijing* states: "Pathogens in the skin should be released via sweating." Yangming main formulas like Baihu Tang use acrid-sweet-cold methods to clear intense Qi-level Heat; the three Chengqi formulas use bitter-salty-cold methods to purge Fu-excess Dryness-Firmness.
However, since Yangming disease is dominated by Dryness-Heat, treatment targets Yangming pathogenic Heat. Whether purging有形 (form-bound) Dryness-Firmness or clearing无形 (formless) Qi-Heat, both fall under the treatment principle of "Heat is treated with Cold." Shaoyang disease is at half-exterior/half-interior with pivot dysfunction. Since it is not in the exterior, sweating is contraindicated; since not in the interior, purging is contraindicated. Thus, treatment focuses on harmonizing. Due to combinations with exterior/interior or fluid retention, formulas vary: Chaihu Guizhi Tang, Dachaihu Tang, Chaihu Jia Mangxiao Tang, Chaihu Guizhi Ganjiang Tang, etc. But all Chaihu formulas derive from modifications of Xiaochaihu Tang, retaining the essence of the Harmonizing Method. Taiyin disease involves Zang-Cold, requiring warming the middle; main formula is Lizhong Wan. If leaning towards interior deficiency with Spleen/Kidney Yang depletion, fire is supplemented to warm earth ("suitable for Sini Tang category"). If combined with exterior syndrome, exterior-interior dual resolution is used, e.g., Guizhi Renshen Tang. The core principle remains warming the interior. Shaoyin Cold-Transformation syndromes vary by病程 (course), pathogen severity, and healthy qi damage degree, using Ma Huang Fu Zi Xi Xin Gan Cao Tang for warming Yang/releasing exterior, Fuzi Tang for warming Yang/nourishing deficiency, or Sini Tang for restoring Yang/rescuing collapse. Since all belong to Shaoyin Yang-deficiency, the focus remains on warming the interior and supporting Yang, following the principle "Cold is treated with Heat."