（２）异中求同、同中有异：异中求同，举例如“伤寒中风，有柴胡证，但见一证便是，不必悉具”（１０１条）用以说明其理。所谓有柴胡证，自以“伤寒五六日中风，往来寒热，胸胁苦满，默默不欲饮食，心烦喜呕……小柴胡汤主之”（９６条）为最标准。其次为２２６条，叙证略同。此外，如“设胸满胁痛者”（３７条），“胁下满”（９９条），“胸胁满不去”（２２９条），“胁下及心痛”（２３１条），“胁下硬满，不大便而呕，舌上白苔者”（２３０条），“呕而发热者”（１４９、３７４条），“妇人中风，七八日，续得寒热，发作有时，经水适断者，此为热入血室”（１４４条）等等，是证候小有差异，而主治均用小柴胡汤。说明只要病在少阳，枢机不利，虽证未全具，自可施用和解一法。但仲景文法，有以此例彼者，有举一隅而通向全盘者。故但见一证便是之例，实贯穿于《伤寒论》多数方证之中，所赅者广。如“太阳中风，阳浮而阴弱，阳浮者，热自发，阴弱者，汗自出，啬啬恶寒，淅淅恶风，翕翕发热，鼻鸣干呕者，桂枝汤主之”（１２条）。其“头痛、发热、汗出、恶风”（１３条），“伤寒发汗已解，半日许复烦，脉浮数者”（５７条），更有“时发热自汗出而不愈者”（５４条），“病常自汗出第三卷１７９者”（５３条）均用桂枝汤，足可证明只要病位在表，营卫不和，无论伤寒杂病，有无表证，皆可施用调和营卫一法。另如“太阳中风，脉浮紧，发热恶寒，身疼痛，不汗出而烦躁者，大青龙汤主之”（３８条）。“伤寒，脉浮缓，身不疼，但重，乍有轻时，无少阴证者，大青龙汤发之”（３９条）。
又《金匮》“病溢饮者，当发其汗，大青龙汤主之。”（《痰饮咳嗽病篇》）此三条脉证大有差异，其发病原因，或由风寒、或关水饮，又有不同。但其病机总为外寒束表，里热内郁，均以“不汗出而烦躁”为主证则一。故可同用大青龙汤以解表清里、表里双解。再有“太阳病三日，发汗不解，蒸蒸发热者，属胃也，调胃承气汤主之”（２４８条）。其“伤寒吐后，腹胀满者”（２４９条），“阳明病，不吐不下，心烦者”（２０７条），皆可与调胃承气汤。以上数条叙证不同，但其病机总为胃热燥结，其主证当有阳明肠胃成实，大便不通，故可同用和胃通下之法。
又如“太阳病发汗，汗出不解，其人仍发热，心下悸，头眩，身动，振振欲擗地者，真武汤主之”（８２条）。“少阴病，二三日不已，至四五日，腹痛，小便不利，四肢沉重疼痛，自下利者，此为有水气，……真武汤主之”（３１６条）。两条之发病原因及所表现证候不同，一属太阳过汗，阳气浮而寒水内动；一属少阴里虚，水气泛滥。但病机总为肾阳虚衰，水气冲逆。其主证当同为小便不利，可以会意。故二者皆用真武汤以温阳散水，健脾利湿。又“食谷欲呕，属阳明也，吴茱萸汤主之”（２４３条）。“少阴病，吐利，手足逆冷，烦躁欲死者，吴茱萸汤主之”（３０９条）。“干呕，吐涎沫，头痛者，吴茱萸汤主之”（３７８条）。此三者一为阳明中寒气逆；一为下焦阳气虚衰，阴寒之气冲逆于胃；一为厥阴浊阴之气，循经上逆。其总的病机为中虚气逆，胃中不和致呕则一。
故可同用吴茱萸汤，以和胃散寒，降逆止呕。
以上为六经证治中异中求同之例，若在此基础上进一步推究其同中之异，则对证候之辨析，更为细致；对所采用之治疗方法，自能适合病情，使其恰到好处。如上所举“太阳中风，……桂枝汤主之。”（１２条）是因表受风寒，其病机阳浮而阴弱，亦即营卫不和，卫强营弱。故用桂枝汤辛甘温之剂，以解肌祛风，调和营卫。并用啜热粥及温覆取遍身微汗之法，以鼓舞胃气而加强助正祛邪之力。若“病常自汗出者”，当属卫气不和，卫外不固，卫气不与营气相谐和，则“宜桂枝汤”调和营卫即可，似不必采用温覆取汗之法，以免汗多亡阳损阴之弊。至于“病人脏无他病，时发热自汗出而不愈者”，亦属卫气不和，用桂枝汤，采取“先其时发汗”之法，助正祛邪，此与《内经》“凡治疟，先其发时如食顷而刺之，一刺则衰，二刺则知，三刺则已”之义较合。
伤寒杂病用桂枝汤相同，因具体病况不同，故治法又有不同。
前述阳明腑实调胃承气三证，其治法重在和胃泻热，故以“温顿服之”为主，亦有“若胃气不和，谵语者，少与调胃承气汤”（２９条）一法。此外，大承气汤为阳明峻下热结之方，其主证如“阳明病，脉迟，虽汗出不恶寒者，其身必重，短气腹满而喘，有潮热者，此外欲解可攻里也。手足然汗出者，此大便已硬也，大承气汤主之”（２０８条）。但仲景使用下法，颇为审慎，如证未全具，并有欲用大承气、先与小承气之试探法。更有阳明腑实病重而势甚急，阳热亢盛，阴液潜消，又有阳明、少阴六急下证之急下存阴法。是用大承气汤同，而治法中心大意，自有种种不同。
又少阴虚寒重证，用回阳救逆法，主方为四逆汤。其主证如“大汗，若大下利，而厥冷者，四逆汤主之”（３５４条）。但“自利不渴者，属太阴，以其脏有寒故也，当温之，宜服四逆辈”（２７７条），何也？考太阴主方为理中汤（丸），今云宜四逆辈，正与《金匮》肝病实脾之旨相合，恐病势由太阴而演变为少阴阳衰阴盛重证之义。又有“少阴病，脉沉者，急温之，宜四逆汤”（３２３条）。
第三卷１８０以证少阴虚寒，救阳之法不可稍缓，虽无下利厥逆，亦当采用急温之法。更有“既吐且利，小便复利，而大汗出，下利清谷，内热外寒，脉微欲绝者，四逆汤主之”（３８９条）。此条见于《霍乱病》篇，当是阴寒直中一类严重病候。吐利暴发，最易导致“阴盛于内，阳亡于外”之危急病势，其“里寒外热”当是真寒假热，病为格阳，用四逆汤，当如方后“强人可大附子一枚，干姜三两”之例，亦即通脉四逆汤方义，重用姜附以存阴回阳。服法当取热药冷服之法，所谓“治凉以热，冷而行之。”（《素问·五常政大论》）庶药气与病气无杆格之虞。以上同属四逆汤证，因证候有轻重，病势有缓急，故治法中心大意又有种种不同矣。
４探六经证治常与变《伤寒论》在六经分证总的原则下，其所载之证候、脉象有常有变，治法亦有常有变。所谓常，是指疾病的证候、脉象一般情况及与之相适应的治法。所谓变，即指较为特殊的病证状况当有随证而变的治法。但机体是复杂的，病变是多种多样的，在一定的病证下，治法又具有灵活性。学习时要从六经病证的全局观点出发，既要通其常，又要知其变，方能曲尽病情，体会出病机变化治疗法则的关键所在。
（１）脉证有变，治法不变：在讨论六经证治之常变中，李氏认为研究重点当着重于变。六经病中，有脉证有变而主证不变，其治法自亦不变者：例如“太阳之为病，脉浮，头项强痛而恶寒”。
（宋本，下同，第１条），头项强痛为太阳表病主证之一，故“病如桂枝证，头不痛，项不强”（１６６条）则非表证。但表病有只头痛而项不强者，如“太阳病，头痛，发热，汗出，恶风，桂枝汤主之”（１３条）是也。恶寒亦为太阳表病主证。伤寒注家并有伤寒恶寒中风之说。但中风证有“啬啬恶寒”（１２条）者，伤寒证亦有“恶风”（３５条）。恶风较轻，恶寒较重，二者在程度上有不同，其性质无大差异，是又不必拘于此矣。表证恶寒多与发热伴见。但在表病初起阶段，如太阳伤寒亦有“或未发热”（３条）者。太阳表病主脉为浮，伤寒则“脉阴阳俱紧”，是浮紧为太阳伤寒主脉。
所谓“脉浮紧，法当身疼痛，宜以汗解之”（５０条）。但亦有脉浮或脉浮数者：如“脉浮者，病在表，可发汗，宜麻黄汤”（５２条）是也。又如“太阳中风，脉浮紧，发热恶寒，身疼痛，不汗出而烦躁者，大青龙汤主之”（３８条）。“伤寒，脉浮缓，身不疼，但重，乍有轻时，无少阴证者，大青龙汤发之”（３９条）。以上两条脉证大有差异，而治法一样，何也？因其病机同为表闭阳郁而有内热，主证之“不汗出而烦躁”，当为两条所共有。故可同用大青龙汤以大发其汗，兼清散郁热为治也。阳明病提纲为胃家实，其病多值燥热极盛阶段，以“身热，汗自出，不恶寒，反恶热”（１８２条）为外证，以“脉大”（１８６条）为主脉，但有热结于里，使阴阳气不相顺接，演变为厥深热深，如“伤寒，脉滑而厥者，里有热，白虎汤主之”（３５０条）。亦有因壮热太盛，汗液大泄，导致津气两伤，其证有见“背微恶寒”（１６９）者，有“时时恶风”（１６８条）者，则白虎汤加人参汤清热兼以益气生津。凡此均须与表证作仔细鉴别，故曰：“伤寒脉浮，发热无汗，其表不解，不可与白虎汤”（１７０条）自可窥其深意。若阳明里热燥结成实，脉多见沉实滑数。所谓“脉沉实者，以下解之”（３９４条）。“阳明病，谵语，发潮热，脉滑而疾者，小承气汤主之”（２１４条）。然里热燥结于府，营卫气血流行之机不畅，又可出现脉迟。如“阳明病，脉迟，虽汗出不恶寒者，其身必重，短气腹满而喘，有潮热者，此外欲解，可攻里也。手足然汗出者，此大便已硬也，大承气汤主之”（２０８条）。但燥热结实之证，则其脉迟必实而有力，此义又所当知也。少阳病以“往来寒热，胸胁苦满，默默不欲饮食，心烦喜呕”（９６条）等为主证。但论中只有“设胸满胁痛者”（３７条）“胁下满”（９９条）者，“胸胁满不去”（２２９条）者，“胁下硬满，不大便而呕”者（２３０条），“呕而发热第三卷１８１者”（１４９、３７９条），“寒热发作有时”（１４４条）者，治法均主用和解，主方为小柴胡汤。综上所述，可以证明少阳枢机不利，只要主证有一二存在，虽证候有些差异，而治法大体不变。此即仲景所谓“伤寒中风，有柴胡证，但见一证便是，不必悉具”（１０１条）之例。但见一证便是，李氏意当不仅局限于柴胡一证。考前段所举大青龙两条，以及桂枝汤治太阳中风外，并治“时发热、自汗出”（５４条）或“常自汗出”（５３条），总的病机为脏无他病，在表营卫不和所致，故都可施用调和营卫之法。推之“自利不渴者，属太阴，以其脏有寒故也，当温之，宜服四逆辈”（２７７条）。自利不渴，自属太阴主证，治法宜用温中，主方如理中汤（丸）。若脏寒太甚，侵及下焦肾命真阳，治法急宜温补脾肾，补火燠土。故在下利证候的基础上，如“下利，腹胀满，……先温其里，……温里宜四逆汤”（３７２条）。“伤寒，病下之，续得下利清谷不止，……急当救里，……救里宜四逆汤”（９１条）。可见虚寒下利，脾肾阳微，虽证候略有小异，治法均可施用四逆汤以温补脾肾，回阳救逆。但见一证便是，与李氏所提脉证有变而主证大抵不变，则其治法不变之说，极有联系，故特此郑重提出，以供参考。
（2）在差异中寻找共性，在共性中辨析差异：所谓“异中求同”，举例来说，《伤寒论》第101条提到：“患伤寒或中风，出现柴胡汤证，只要见到其中一个症状即可，不必所有症状都具备。”以此说明其道理。所谓的柴胡证，以第96条最为标准：“伤寒五六天或中风，寒热往来，胸胁部苦闷胀满，神情沉默不想饮食，心烦且喜欢呕吐……主治用小柴胡汤。”其次是第226条，叙述的症状大致相同。此外，如第37条的“如果胸满胁痛”，第99条的“胁下胀满”，第229条的“胸胁满闷不除”，第231条的“胁下及心痛”，第230条的“胁下硬满，大便不通且呕吐，舌上有白苔”，第149条和第374条的“呕吐且发热”，以及第144条的“妇女中风，七八天后，持续出现寒热，发作有定时，月经恰好中断，这是热邪进入血室”等等，这些证候虽有细微差别，但主治均使用小柴胡汤。这说明只要病位在少阳，枢机运转不利，即使症状未完全具备，自然可以使用和解的方法。但是张仲景的行文法度，有用此例彼的，也有举一反三贯通全篇的。所以“但见一证便是”的例子，实际上贯穿于《伤寒论》多数方证之中，涵盖范围很广。例如第12条：“太阳中风，脉象阳浮而阴弱，阳浮者，热自发，阴弱者，汗自出，怕冷啬啬，怕风淅淅，发热翕翕，鼻鸣干呕的，主治用桂枝汤。”其第13条的“头痛、发热、汗出、恶风”，第57条的“伤寒发汗后已解，半天左右又烦，脉浮数的”，更有第54条的“时常发热自汗出而不愈的”，第53条的“病人经常自汗出的”，均使用桂枝汤，足可证明只要病位在表，营卫不和，无论是伤寒还是杂病，有无典型表证，都可以施用调和营卫的方法。另外如第38条：“太阳中风，脉浮紧，发热恶寒，身体疼痛，无汗且烦躁的，主治用大青龙汤。”第39条：“伤寒，脉浮缓，身体不疼，只是沉重，偶尔有轻的时候，没有少阴证的，用大青龙汤发散。”
另外《金匮要略》中提到：“患溢饮病的，应当发汗，主治用大青龙汤。”（出自《痰饮咳嗽病篇》）。这三条的脉证有很大差异，发病原因也不同，有的由风寒引起，有的与水饮有关。但其病机总体都是外寒束缚肌表，里热内郁，都以“无汗且烦躁”为主要症状是一致的。因此可以共同使用大青龙汤来解表清里、表里双解。还有第248条：“太阳病三天，发汗后病不解，蒸蒸发热的，属于胃，主治用调胃承气汤。”第249条的“伤寒吐后，腹胀满的”，第207条的“阳明病，不吐不下，心烦的”，都可以与调胃承气汤。以上几条叙述的症状不同，但其病机总体为胃热燥结，主要症状应当有阳明肠胃成实，大便不通，因此可以共同使用和胃通下的方法。
又如第82条：“太阳病发汗，汗出后病不解，其人仍然发热，心下悸动，头晕，身体震颤动摇，振颤欲倒地的，主治用真武汤。”第316条：“少阴病，两三天未愈，到四五天，腹痛，小便不利，四肢沉重疼痛，自下利的，这是有水气……主治用真武汤。”这两条的发病原因及所表现的证候不同，一条属于太阳过汗，阳气浮越而寒水内动；一条属于少阴里虚，水气泛滥。但病机总体都是肾阳虚衰，水气冲逆。其主要症状应当同为小便不利，可以领会。因此两者都用真武汤来温阳散水，健脾利湿。又第243条：“进食后想呕吐，属于阳明，主治用吴茱萸汤。”第309条：“少阴病，吐利，手足逆冷，烦躁得快要死的，主治用吴茱萸汤。”第378条：“干呕，吐涎沫，头痛的，主治用吴茱萸汤。”这三者一条是阳明中寒气逆；一条是下焦阳气虚衰，阴寒之气冲逆于胃；一条是厥阴浊阴之气，循经上逆。其总的病机是中焦虚寒气逆，胃中不和导致呕吐是一致的。
因此可以共同使用吴茱萸汤，以和胃散寒，降逆止呕。
以上是六经证治中异中求同的例子，若在此基础上进一步推究其同中之异，则对证候的辨析更为细致；对所采用的治疗方法，自然能适合病情，使其恰到好处。如上所述第12条“太阳中风，……主治用桂枝汤。”是因为体表受风寒，其病机是阳浮而阴弱，也就是营卫不和，卫强营弱。因此用桂枝汤这种辛甘温的药剂，以解肌祛风，调和营卫。并配合喝热粥及温覆取遍身微微出汗的方法，以鼓舞胃气从而加强助正祛邪的力量。如果“病人经常自汗出的”，应当属于卫气不和，卫外不固，卫气不与营气相和谐，那么“宜用桂枝汤”调和营卫即可，似乎不必采用温覆取汗的方法，以免汗多亡阳损阴的弊端。至于“病人内脏没有其他疾病，时常发热自汗出而不愈的”，也属于卫气不和，用桂枝汤，采取“在其发作前发汗”的方法，助正祛邪，这与《内经》中“凡是治疗疟疾，在发作前大约一顿饭的时间针刺，刺一次则衰退，刺两次则好转，刺三次则痊愈”的意义比较吻合。
伤寒杂病使用桂枝汤虽然相同，但因具体病情不同，所以治法又有不同。
前述阳明腑实调胃承气汤的三种证候，其治法重在和胃泻热，因此以“温热顿服”为主，也有第29条“如果胃气不和，说胡话的，少量给予调胃承气汤”的方法。此外，大承气汤是阳明峻下热结的方剂，其主要症状如第208条：“阳明病，脉迟，虽然出汗但不恶寒的，其身必定沉重，短气腹满而喘，有潮热的，这表示表证将解可以攻里了。手足濈然汗出的，这表示大便已经硬结，主治用大承气汤。”但是张仲景使用下法颇为审慎，如证候未完全具备，并有想用大承气汤时，先用小承气汤试探的方法。更有阳明腑实病重而势甚急，阳热亢盛，阴液潜消，又有阳明、少阴六急下证之急下存阴法。是用大承气汤相同，而治法的中心大意，自有种种不同。
另外少阴虚寒重证，用回阳救逆法，主方为四逆汤。其主要症状如第354条：“大汗，或者大下利，而四肢厥冷的，主治用四逆汤。”但第277条说“自利不渴的，属于太阴，因为内脏有寒的缘故，应当温之，宜服用四逆辈”，为什么呢？考察太阴主方为理中汤（丸），现在说宜四逆辈，正与《金匮要略》肝病实脾的宗旨相合，恐怕是病势由太阴演变为少阴阳衰阴盛重证的意思。又有第323条：“少阴病，脉沉的，急温之，宜四逆汤。”
因证属少阴虚寒，救阳之法不可稍缓，虽然没有下利厥逆，也当采用急温的方法。更有第389条：“既吐且利，小便复利，而大汗出，下利清谷，内热外寒，脉微欲绝的，主治用四逆汤。”这一条见于《霍乱病》篇，应当是阴寒直中一类严重病候。吐利暴发，最易导致“阴盛于内，阳亡于外”的危急病势，其“里寒外热”应当是真寒假热，病为格阳，用四逆汤，应当像方后注“强壮的人可用大附子一枚，干姜三两”的例子，也就是通脉四逆汤的方义，重用姜附以存阴回阳。服法应当取热药冷服的方法，所谓“治凉以热，冷而行之。”（《素问·五常政大论》）这样才没有药气与病气抵触的担忧。以上同属四逆汤证，因证候有轻重，病势有缓急，故治法的中心大意又有种种不同矣。
4. 探讨六经证治的常与变：《伤寒论》在六经分证总的原则下，其所记载的证候、脉象有常有变，治法亦有常有变。所谓常，是指疾病的证候、脉象一般情况及与之相适应的治法。所谓变，即指较为特殊的病证状况当有随证而变的治法。但机体是复杂的，病变是多种多样的，在一定的病证下，治法又具有灵活性。学习时要从六经病证的全局观点出发，既要通晓其常，又要知晓其变，方能详尽病情，体会出病机变化治疗法则的关键所在。
（1）脉证有变，治法不变：在讨论六经证治之常变中，李培生先生认为研究重点应当着重于变。六经病中，有脉证有变而主证不变，其治法自然也不变的情况：例如第1条“太阳之为病，脉浮，头项强痛而恶寒”。头项强痛是太阳表病的主证之一，所以第166条“病如桂枝证，头不痛，项不强”则不是表证。但表病有只头痛而项不强的，如第13条“太阳病，头痛，发热，汗出，恶风，主治用桂枝汤”就是。恶寒也是太阳表病的主证。伤寒注家并有伤寒恶寒中风之说。但中风证有第12条“啬啬恶寒”的，伤寒证也有第35条“恶风”的。恶风较轻，恶寒较重，二者在程度上有不同，其性质无大差异，这又不必拘泥于此了。表证恶寒多与发热伴见。但在表病初起阶段，如太阳伤寒也有第3条“或未发热”的。太阳表病主脉为浮，伤寒则“脉阴阳俱紧”，是浮紧为太阳伤寒主脉。所谓第50条“脉浮紧，法当身疼痛，宜以汗解之”。但也有脉浮或脉浮数的：如第52条“脉浮者，病在表，可发汗，宜麻黄汤”就是。又如第38条“太阳中风，脉浮紧，发热恶寒，身疼痛，不汗出而烦躁的，主治用大青龙汤。”第39条“伤寒，脉浮缓，身不疼，但重，乍有轻时，无少阴证的，用大青龙汤发散。”以上两条脉证大有差异，而治法一样，为什么呢？因为其病机同为表闭阳郁而有内热，主证的“不汗出而烦躁”，应当为两条所共有。故可同用大青龙汤以大发其汗，兼清散郁热为治也。阳明病提纲为胃家实，其病多值燥热极盛阶段，以第182条“身热，汗自出，不恶寒，反恶热”为外证，以第186条“脉大”为主脉，但有热结于里，使阴阳气不相顺接，演变为厥深热深，如第350条“伤寒，脉滑而厥的，里有热，主治用白虎汤。”也有因壮热太盛，汗液大泄，导致津气两伤，其证有见第169条“背微恶寒”的，有第168条“时时恶风”的，则白虎加人参汤清热兼以益气生津。凡此均须与表证作仔细鉴别，所以说第170条“伤寒脉浮，发热无汗，其表不解，不可与白虎汤”自可窥其深意。若阳明里热燥结成实，脉多见沉实滑数。所谓第394条“脉沉实的，以下解之”。“阳明病，谵语，发潮热，脉滑而疾的，主治用小承气汤”（第214条）。然而里热燥结于腑，营卫气血流行之机不畅，又可出现脉迟。如第208条“阳明病，脉迟，虽汗出不恶寒的，其身必重，短气腹满而喘，有潮热的，这表示表证将解，可攻里了。手足濈然汗出的，这表示大便已硬，主治用大承气汤。”但燥热结实之证，则其脉迟必实而有力，这个意义也是应当知道的。少阳病以第96条“往来寒热，胸胁苦满，默默不欲饮食，心烦喜呕”等为主证。但论中只有第37条“设胸满胁痛的”，第99条“胁下满”的，第229条“胸胁满不去”的，第230条“胁下硬满，不大便而呕”的，第149条和第379条“呕而发热”的，第144条“寒热发作有时”的，治法均主用和解，主方为小柴胡汤。综上所述，可以证明少阳枢机不利，只要主证有一二存在，虽证候有些差异，而治法大体不变。此即仲景所谓第101条“伤寒中风，有柴胡证，但见一证便是，不必悉具”的例子。但见一证便是，李培生先生的意思应当不仅局限于柴胡一证。考前段所举大青龙两条，以及桂枝汤治太阳中风外，并治第54条“时发热、自汗出”或第53条“常自汗出”，总的病机为脏无他病，在表营卫不和所致，故都可施用调和营卫之法。推之第277条“自利不渴的，属于太阴，因为内脏有寒的缘故，应当温之，宜服用四逆辈”。自利不渴，自属太阴主证，治法宜用温中，主方如理中汤（丸）。若脏寒太甚，侵及下焦肾命真阳，治法急宜温补脾肾，补火燠土。故在下利证候的基础上，如第372条“下利，腹胀满，……先温其里，……温里宜四逆汤”。“伤寒，病下之，续得下利清谷不止，……急当救里，……救里宜四逆汤”（第91条）。可见虚寒下利，脾肾阳微，虽证候略有小异，治法均可施用四逆汤以温补脾肾，回阳救逆。但见一证便是，与李培生先生所提脉证有变而主证大抵不变，则其治法不变之说，极有联系，故特此郑重提出，以供参考。
(2) Seeking commonality amidst differences, and distinguishing differences within commonality: "Seeking commonality amidst differences" can be illustrated by the example in Clause 101 of the *Shanghan Lun* (Treatise on Cold Pathogenic Diseases): "In cases of cold damage or wind strike, if there are Chaihu syndrome manifestations, observing just one symptom is sufficient; it is not necessary for all symptoms to be present." This illustrates the principle. The so-called Chaihu syndrome is best exemplified by Clause 96: "After five or six days of cold damage or wind strike, with alternating chills and fever, bitter fullness and distension in the chest and hypochondrium, silent desire to eat nothing, irritability, and a tendency to vomit... Xiao Chaihu Tang (Minor Bupleurum Decoction) is the primary formula." Secondly, Clause 226 describes similar symptoms. Additionally, such as "if there is chest fullness and hypochondriac pain" (Clause 37), "fullness under the ribs" (Clause 99), "chest and hypochondriac fullness that does not resolve" (Clause 229), "pain under the ribs and in the heart region" (Clause 231), "hardness and fullness under the ribs, constipation accompanied by vomiting, and a white coating on the tongue" (Clause 230), "vomiting accompanied by fever" (Clauses 149, 374), and "in women with wind strike, after seven or eight days, continuing to have chills and fever occurring at specific times, with menstruation having just stopped, this is heat entering the Blood Chamber" (Clause 144), etc. Although these syndromes have slight variations, they are all primarily treated with Xiao Chaihu Tang (Minor Bupleurum Decoction). This demonstrates that as long as the disease is in the Shaoyang (Lesser Yang) stage, with dysfunction of the pivot mechanism, even if not all symptoms are present, the method of harmonization (He Jie) can naturally be applied. However, Zhang Zhongjing's textual style includes using one case to illustrate another, or inferring the whole from a part. Therefore, the example of "observing just one symptom is sufficient" is actually贯穿 (permeates) most of the formula-syndrome combinations in the *Shanghan Lun*, covering a broad scope. For instance, Clause 12 states: "In Taiyang wind strike, the pulse is floating on the exterior and weak on the interior. Floating on the exterior indicates spontaneous heat; weak on the interior indicates spontaneous sweating. With aversion to cold described as 'se se', aversion to wind as 'xi xi', fever as 'xi xi', nasal congestion, and dry vomiting, Guizhi Tang (Cinnamon Twig Decoction) is the primary formula." Similarly, "headache, fever, sweating, and aversion to wind" (Clause 13); "after cold damage and sweating, the condition resolves, but half a day later returns with vexation and a floating, rapid pulse" (Clause 57); "occasional fever with spontaneous sweating that does not resolve" (Clause 54); and "the patient constantly has spontaneous sweating" (Clause 53) are all treated with Guizhi Tang (Cinnamon Twig Decoction). This sufficiently proves that as long as the disease location is in the Exterior (Biao), with disharmony of Ying (Nutritive) and Wei (Defensive) Qi, whether in cold damage or miscellaneous diseases, regardless of whether typical exterior symptoms are present, the method of harmonizing Ying and Wei Qi can be applied. Furthermore, Clause 38 states: "Taiyang wind strike, with a floating-tight pulse, fever, aversion to cold, body pain, no sweating, and irritability, Da Qing Long Tang (Major Blue-Green Dragon Decoction) is the primary formula." Clause 39 states: "Cold damage, with a floating-slow pulse, no body pain but heaviness, occasionally lighter, without Shaoyin syndrome, Da Qing Long Tang (Major Blue-Green Dragon Decoction) is used to disperse."
Additionally, in the *Jingui Yaolue* (Essential Prescriptions of the Golden Cabinet), it is stated: "For patients with Yi Yin (Overflowing Fluids), sweating should be induced, and Da Qing Long Tang (Major Blue-Green Dragon Decoction) is the primary formula" (from the Chapter on Phlegm-Fluids and Coughing). These three clauses have significantly different pulse and syndrome presentations, and their etiologies differ: some arise from wind-cold, others from fluid retention. However, their pathogenesis is generally external cold binding the exterior and internal heat stagnating within, all sharing "no sweating and irritability" as the main symptom. Thus, Da Qing Long Tang (Major Blue-Green Dragon Decoction) can be commonly used to release the exterior and clear the interior, achieving a dual resolution of both layers. Also, Clause 248 states: "After three days of Taiyang disease, if sweating fails to resolve the condition, and there is steaming fever, it belongs to the Stomach, and Tiaowei Chengqi Tang (Regulate the Stomach and Purge Decoction) is the primary formula." Clauses 249 ("abdominal fullness after vomiting in cold damage") and 207 ("vexation in Yangming disease without vomiting or purging") can also be treated with Tiaowei Chengqi Tang (Regulate the Stomach and Purge Decoction). Although the described symptoms in these clauses differ, their pathogenesis is generally stomach heat with dryness and accumulation, with main symptoms involving Yangming intestinal and gastric excess and constipation. Therefore, the method of harmonizing the stomach and purging downward can be commonly applied.
Moreover, Clause 82 states: "After sweating in Taiyang disease, if the condition does not resolve upon sweating, and the person still has fever, palpitations in the epigastrium, dizziness, body tremors, and a sensation of trembling as if about to fall to the ground, Zhenwu Tang (True Warrior Decoction) is the primary formula." Clause 316 states: "In Shaoyin disease, if it persists for two or three days and progresses to four or five days, with abdominal pain, difficulty in urination, heaviness and pain in the four limbs, and spontaneous diarrhea, this is due to water qi... Zhenwu Tang (True Warrior Decoction) is the primary formula." The etiologies and manifested syndromes of these two clauses differ: one belongs to excessive sweating in Taiyang leading to floating yang and internal movement of cold fluids; the other belongs to Shaoyin interior deficiency with flooding of water qi. However, the pathogenesis is generally kidney yang deficiency with counterflow of water qi. Their main symptoms should both include difficulty in urination, which can be understood. Thus, both use Zhenwu Tang (True Warrior Decoction) to warm yang and dissipate water, strengthen the spleen and promote diuresis. Also, Clause 243 states: "Desire to vomit after eating food belongs to Yangming, and Wuzhuyu Tang (Evodia Decoction) is the primary formula." Clause 309 states: "In Shaoyin disease, with vomiting and diarrhea, cold extremities, and severe irritability bordering on death, Wuzhuyu Tang (Evodia Decoction) is the primary formula." Clause 378 states: "Dry heaving, vomiting of saliva and froth, and headache, Wuzhuyu Tang (Evodia Decoction) is the primary formula." These three represent: one is middle jiao cold with counterflow of qi; one is deficiency of lower jiao yang with counterflow of yin-cold qi to the stomach; one is Jueyin turbid yin qi counterflowing along the meridians. Their general pathogenesis is middle jiao deficiency with counterflow of qi and stomach disharmony leading to vomiting.
Therefore, Wuzhuyu Tang (Evodia Decoction) can be commonly used to harmonize the stomach, dissipate cold, descend counterflow, and stop vomiting.
The above are examples of seeking commonality amidst differences in the treatment of Six Meridian syndromes. If one further investigates the differences within commonality on this basis, the differentiation of syndromes becomes more detailed, and the chosen treatment methods can better suit the condition, achieving precision. As mentioned above, Clause 12 "Taiyang wind strike... Guizhi Tang (Cinnamon Twig Decoction) is the primary formula" occurs because the exterior is affected by wind-cold, with a pathogenesis of floating yang and weak yin, i.e., disharmony of Ying and Wei Qi, with strong Wei and weak Ying. Therefore, Guizhi Tang (Cinnamon Twig Decoction), a pungent, sweet, and warm preparation, is used to release the muscle layer, dispel wind, and harmonize Ying and Wei Qi. It is combined with drinking hot porridge and covering warmly to induce mild, uniform sweating throughout the body, thereby boosting Stomach Qi to enhance the power of supporting healthy qi and expelling pathogenic factors. If "the patient constantly has spontaneous sweating," it should belong to disharmony of Wei Qi, with insecure exterior defense, where Wei Qi does not harmonize with Ying Qi. Then, simply using Guizhi Tang (Cinnamon Twig Decoction) to harmonize Ying and Wei Qi is appropriate, and it may not be necessary to adopt the method of covering warmly to induce sweating, to avoid the detriment of excessive sweating damaging yang and yin. As for "the patient has no internal organ pathology, but has occasional fever with spontaneous sweating that does not resolve," this also belongs to disharmony of Wei Qi. Using Guizhi Tang (Cinnamon Twig Decoction) and adopting the method of "inducing sweating before the onset" supports healthy qi and expels pathogens, which aligns with the meaning in the *Neijing* (Inner Canon): "When treating malaria, puncture approximately the time of a meal before the attack begins; one puncture reduces it, two punctures improve it, three punctures cure it."
Although Guizhi Tang (Cinnamon Twig Decoction) is used similarly for cold damage and miscellaneous diseases, the treatment methods differ due to specific conditions.
Regarding the three syndromes of Yangming fu-organ excess treated with Tiaowei Chengqi Tang (Regulate the Stomach and Purge Decoction), the treatment focuses on harmonizing the stomach and purging heat, thus emphasizing "taking it warm in one dose." There is also the method from Clause 29: "If the Stomach Qi is disharmonious and there is delirium, give a small amount of Tiaowei Chengqi Tang (Regulate the Stomach and Purge Decoction)." Additionally, Dachengqi Tang (Major Order the Qi Decoction) is a formula for severe purging of heat and accumulation in Yangming. Its main symptoms are described in Clause 208: "Yangming disease, with a slow pulse, although sweating occurs and there is no aversion to cold, the body must be heavy, short of breath, abdominal fullness with panting, and tidal fever. This indicates the exterior is resolving and the interior can be attacked. If there is continuous sweating of the hands and feet, this indicates the stool has hardened, and Dachengqi Tang (Major Order the Qi Decoction) is the primary formula." However, Zhang Zhongjing was very cautious in using purgative methods. If symptoms were not fully present, and there was a desire to use Dachengqi Tang (Major Order the Qi Decoction), he employed a probing method using Xiaochengqi Tang (Minor Order the Qi Decoction) first. Furthermore, in severe Yangming fu-organ disease with urgent progression, hyperactive yang-heat, and latent consumption of yin-fluids, there is the method of urgent purging to preserve yin in the Six Urgent Syndromes of Yangming and Shaoyin. Thus, while Dachengqi Tang (Major Order the Qi Decoction) is the same, the central intent of the treatment varies.
Furthermore, for severe Shaoyin deficiency-cold syndromes, the method of restoring yang and rescuing from collapse is used, with Sini Tang (Recover the Four Decoction) as the primary formula. Its main symptoms are described in Clause 354: "Profuse sweating, or severe diarrhea, with cold extremities, Sini Tang (Recover the Four Decoction) is the primary formula." But Clause 277 states: "Spontaneous diarrhea without thirst belongs to Taiyin, because the zang organs have cold; therefore, warming is indicated, and Sini category formulas are suitable." Why? The primary formula for Taiyin is Lizhong Tang (Regulate the Middle Decoction). Now saying "Sini category" aligns with the principle in the *Jingui Yaolue* of strengthening the Spleen when treating Liver disease, suggesting the fear that the disease trend may evolve from Taiyin into a severe Shaoyin syndrome of yang deficiency and yin excess. Also, Clause 323 states: "Shaoyin disease, with a sinking pulse, urgently warm it; Sini Tang (Recover the Four Decoction) is suitable."
Because the syndrome is Shaoyin deficiency-cold, the method of saving yang cannot be delayed. Even without diarrhea and cold extremities, the method of urgent warming should be adopted. Moreover, Clause 389 states: "With both vomiting and diarrhea, frequent urination, profuse sweating, diarrhea with undigested food, internal heat and external cold, and a faint pulse nearly imperceptible, Sini Tang (Recover the Four Decoction) is the primary formula." This clause appears in the Chapter on Huoluan Disease (Cholera-like Disease) and represents a severe condition of direct invasion by yin-cold. Sudden onset of vomiting and diarrhea easily leads to the critical situation of "yin excess internally and yang collapse externally." The "internal cold and external heat" here should be true cold with false heat, representing blocking yang. When using Sini Tang (Recover the Four Decoction), one should follow the post-formula note: "Strong individuals may use one large Fuzi (Aconite Root) and three liang of Ganjiang (Dried Ginger)," which corresponds to the formulation principle of Tongmai Sini Tang (Pulse-Restoring Sini Decoction), heavily using Jiang (Ginger) and Fu (Aconite) to preserve yin and restore yang. The administration method should take the approach of taking hot medicine cold, as stated: "Treat cold with heat, administer it cold" (*Suwen: Chapter on Great Policy of Five Constants*). This avoids the risk of conflict between the medicinal qi and the pathogenic qi. Above, all belong to Sini Tang (Recover the Four Decoction) syndromes, but because syndromes vary in severity and disease trends in urgency, the central intent of the treatment methods differs accordingly.
4. Exploring the Constant and Variable in Six Meridian Syndrome Treatment: Under the general principle of Six Meridian differentiation in the *Shanghan Lun*, the recorded syndromes and pulses have constants (Chang) and variables (Bian), and the treatment methods also have constants and variables. The "constant" refers to the general presentation of disease syndromes and pulses and the corresponding treatment methods. The "variable" refers to special pathological conditions requiring treatment methods that change according to the syndrome. However, the human body is complex, and pathological changes are diverse; under certain syndromes, treatment methods possess flexibility. In study, one must start from a holistic view of Six Meridian diseases, understanding both the constant and the variable, to fully comprehend the condition and grasp the key principles of treatment amidst pathogenic changes.
(1) Pulse and Syndrome Change, Treatment Method Unchanged: In discussing the constant and variable in Six Meridian treatment, Mr. Li Peisheng believed the research focus should be on the variable. Among Six Meridian diseases, there are cases where the pulse and syndrome change but the main syndrome remains unchanged, and thus the treatment method remains unchanged: For example, Clause 1 states: "Taiyang disease is characterized by a floating pulse, stiffness and pain in the head and nape, and aversion to cold." Head and nape stiffness/pain is one of the main symptoms of Taiyang exterior disease. Therefore, Clause 166 "symptoms resembling Guizhi syndrome, but without headache or nape stiffness" is not an exterior syndrome. However, exterior diseases can present with only headache without nape stiffness, such as Clause 13 "Taiyang disease, headache, fever, sweating, aversion to wind, Guizhi Tang (Cinnamon Twig Decoction) is the primary formula." Aversion to cold is also a main symptom of Taiyang exterior disease. Commentators on cold damage distinguish between aversion to cold in cold damage and aversion to wind in wind strike. However, wind strike syndromes have "aversion to cold described as 'se se'" (Clause 12), and cold damage syndromes have "aversion to wind" (Clause 35). Aversion to wind is milder, aversion to cold is heavier; they differ in degree but not significantly in nature, so one need not rigidly adhere to this distinction. Exterior syndrome aversion to cold often accompanies fever. But in the initial stage of exterior disease, such as Taiyang cold damage, there is also "possibly no fever yet" (Clause 3). The main pulse for Taiyang exterior disease is floating; for cold damage, it is "pulse tight on both yin and yang positions," making floating-tight the main pulse for Taiyang cold damage. As stated in Clause 50: "Floating-tight pulse, law dictates body pain, should be resolved by sweating." But there are also floating or floating-rapid pulses: such as Clause 52 "Floating pulse, disease is in the exterior, can induce sweating, Ma Huang Tang (Ephedra Decoction) is suitable." Also, Clause 38 "Taiyang wind strike, floating-tight pulse, fever, aversion to cold, body pain, no sweating, and irritability, Da Qing Long Tang (Major Blue-Green Dragon Decoction) is the primary formula." Clause 39 "Cold damage, floating-slow pulse, no body pain but heaviness, occasionally lighter, without Shaoyin syndrome, Da Qing Long Tang (Major Blue-Green Dragon Decoction) disperses." The pulse and syndrome in these two clauses differ greatly, yet the treatment method is the same. Why? Because their pathogenesis is identical: exterior closure with yang depression and internal heat. The main symptom "no sweating and irritability" is shared by both. Thus, Da Qing Long Tang (Major Blue-Green Dragon Decoction) can be commonly used to induce heavy sweating and simultaneously clear and disperse stagnant heat. The outline for Yangming disease is "Stomach Home Excess," and the disease often reaches a stage of extreme dryness-heat, with "body heat, spontaneous sweating, no aversion to cold, but aversion to heat" (Clause 182) as exterior signs, and "large pulse" (Clause 186) as the main pulse. However, if heat accumulates internally, preventing smooth connection between yin and yang qi, evolving into deep jue with deep heat, such as Clause 350 "Cold damage, slippery pulse with jue (cold extremities), heat in the interior, Baihu Tang (White Tiger Decoction) is the primary formula." Also, due to excessive heat causing massive sweating, leading to injury of both jin-ye (fluids) and qi, the syndrome may show "slight aversion to cold on the back" (Clause 169) or "occasional aversion to wind" (Clause 168), then Baihu Jia Renshen Tang (White Tiger plus Ginseng Decoction) clears heat while supplementing qi and generating fluids. All these require careful differentiation from exterior syndromes, hence Clause 170 states: "Cold damage, floating pulse, fever, no sweat, if the exterior is not resolved, Baihu Tang (White Tiger Decoction) must not be given," revealing its deep meaning. If Yangming interior heat causes dryness and accumulation, the pulse is often sinking, solid, slippery, and rapid. As stated in Clause 394: "Sinking-solid pulse, resolve by purging." Clause 214: "Yangming disease, delirium, tidal fever, slippery and rapid pulse, Xiaochengqi Tang (Minor Order the Qi Decoction) is the primary formula." However, if interior heat and dryness accumulate in the fu-organs, impeding the circulation of Ying, Wei, Qi, and Blood, a slow pulse may appear. Such as Clause 208: "Yangming disease, slow pulse, although sweating occurs and there is no aversion to cold, the body must be heavy, short of breath, abdominal fullness with panting, and tidal fever. This indicates the exterior is resolving, and the interior can be attacked. Continuous sweating of the hands and feet indicates the stool has hardened, Dachengqi Tang (Major Order the Qi Decoction) is the primary formula." But in cases of dryness-heat accumulation, the slow pulse must be solid and forceful; this meaning should be known. Shaoyang disease takes "alternating chills and fever, bitter fullness and distension in the chest and hypochondrium, silent desire to eat nothing, irritability, and a tendency to vomit" (Clause 96) as main symptoms. But in the treatise, only "if there is chest fullness and hypochondriac pain" (Clause 37), "fullness under the ribs" (Clause 99), "chest and hypochondriac fullness that does not resolve" (Clause 229), "hardness and fullness under the ribs, constipation and vomiting" (Clause 230), "vomiting and fever" (Clauses 149, 379), and "chills and fever occurring at specific times" (Clause 144) are mentioned, all treated primarily with harmonization, using Xiao Chaihu Tang (Minor Bupleurum Decoction) as the main formula. In summary, this proves that in Shaoyang pivot dysfunction, as long as one or two main symptoms exist, despite slight syndrome variations, the treatment method remains largely unchanged. This is the example cited by Zhongjing in Clause 101: "In cold damage or wind strike, if there are Chaihu syndrome manifestations, observing just one symptom is sufficient; it is not necessary for all symptoms to be present." However, "observing just one symptom is sufficient," in Mr. Li's opinion, should not be limited to just one Chaihu symptom. Referring to the two Da Qing Long Tang clauses mentioned earlier, and besides Guizhi Tang treating Taiyang wind strike, it also treats "occasional fever and spontaneous sweating" (Clause 54) or "constant spontaneous sweating" (Clause 53). The general pathogenesis is no internal organ pathology, but disharmony of Ying and Wei Qi in the exterior. Thus, the method of harmonizing Ying and Wei Qi can be applied. Extending this logic, Clause 277 "spontaneous diarrhea without thirst belongs to Taiyin, because the zang organs have cold; therefore, warming is indicated, and Sini category formulas are suitable." Spontaneous diarrhea without thirst belongs to Taiyin main symptoms, and the treatment method should be warming the middle, with Lizhong Tang (Regulate the Middle Decoction) as the main formula. If the zang cold is too severe, invading the true yang of the Kidney and Mingmen in the lower jiao, the treatment method urgently requires warming and tonifying the Spleen and Kidney, supplementing fire to warm the earth. Therefore, based on the diarrhea syndrome, such as Clause 372 "diarrhea, abdominal fullness... first warm the interior... for warming the interior, Sini Tang (Recover the Four Decoction) is suitable" and Clause 91 "Cold damage, after purging, continues with diarrhea of undigested food... urgently save the interior... for saving the interior, Sini Tang (Recover the Four Decoction) is suitable." It can be seen that in deficiency-cold diarrhea with weak Spleen and Kidney yang, despite slight syndrome variations, the treatment method can apply Sini Tang (Recover the Four Decoction) to warm and tonify Spleen and Kidney, restore yang, and rescue from collapse. The concept of "observing just one symptom is sufficient" is closely linked to Mr. Li's proposition that although pulse and syndrome may change, the main syndrome remains largely unchanged, and thus the treatment method remains unchanged. Therefore, this is specially proposed for reference.