《易》这个系统在讨论两仪四象以后，就跳到八卦这个层面，当然，八卦也有三阴三阳，但是，阐述的角度显然与医有很大的差别。所以，医系统的三阴三阳应该说是很独特的。我们看《素问》，在《素问》的前几篇里，只讲二阴二阳，特别是《四气调神大论》，它只提少阳少阴，太阳太阴，直到第六篇《阴阳离合论》才明确提出三阴三阳。就是在二阴二阳的基础上增加一个厥阴，一个阳明。阴阳这个概念在传统文化的各个领域都能找到，可以说各行各业都在用它，但是，像厥阴、阳明这样一对概念，则几乎只限于医家之用。可见这两个概念对中医的关系很大。什么叫阳明？什么叫厥阴呢？《素问》里面有专门的定义：两阳相合为阳明，两阴交尽为厥阴。而其他的二阴二阳，《素问》里没有专门的定义。这就说明了厥阴阳明的引入，对于中医理论的构建具有非常特殊的意义。中医有一个最基本的观念，或者说最基本的特点，这个观念我们前面已经提到过，就是整体观念，天人合一。这样一个观念，实际上我们在传统文化的各个领域都能见到，儒家的学问，道家的学问，都是秉承这样一个基本的东西。可以说，这个观念是整个传统文化大厦的基石。前面我们讨论伤寒的时候，引述了许多《四气调神大论》的观点，实际上都是说的这个观念。前章已经说过，春夏为什么要养阳？秋冬为什么要养阴？春为什么要养生？夏为什么要养长？为的是与天地同步。天地生你也生，天地怎么变化，你也怎么变化，这就是天人相应，这就是整体观念，这就是道！得道多助，失道寡助；顺天者昌，逆天者亡，从原始自然的意义讲，就是说的这个问题。那么，我们要跟上天地的变化，首先必须知道天地怎样变化。天地变化的最明显的单位，或者说最明显的层次就是年。每一年天地都要作一个很大的变化，比如今年庚辰年，变到明年就是辛巳年。庚辰年是金运太过，太阳寒水司天，太阴湿土在泉，而辛巳年就变成了水运不及，厥阴风木司天，少阳相火在泉。一个金运、一个水运，一个太过，一个不及，这个变化太大了。在年这样一个大变化的框架里，还有一个更基本、更细小的变化单位，这就是气。气这个概念我们在第一章里已经讨论过，它本来是岐伯保密的东西，但是，在黄帝的追问下，不得不说出来。一年由二十四个气组成，在年这个框架里，气就是最基本的变化单位，天地便是按照这样一个单位在不断地变化。由小雪到大雪，由小寒到大寒。人要与天地相应，就必须得跟上这个变化。天地交换到另一个气的时候，你也要跟上来，还停在原来的这个气上，这就叫做“不及”。如果天地还没有跨越到另外一个气上，你先走了，这叫“太过”。太过与不及都没有与天地保持一致，没有与天地相应。那么，在气这个层次上，人体靠什么来与天地自然保持一致呢？就靠肺。《素问·灵兰秘典论》、《素问·六节藏象论》讲“肺者，治节出焉”，“肺者，气之本”。实际上就是揭示肺的这个功能。有关这个问题，我们在第一章已专门地分析过，肺在运气里，在《阴阳大论》里，它属于阳明。阳明燥金，主肺与大肠。所以，阳明这个概念的引入，对于在气这个层次上建立天人合一的专门机制是非常重要的。阳明为着沟通气这个层次的天人关系，那么，厥阴呢？厥阴为风木，主肝胆。《素问·六节藏象论》云：“肝者，罢极之本，魂之居也。”罢极是什么意思呢？按照前人的很多说法，包括现代《中基》教材的说法，都认为这个罢极是当“疲极”讲，疲劳到了极限，这个说法我们认为不符合逻辑。为什么呢？因为《六节藏象论》这一篇都是探讨藏府的正常功能，一个生之本，一个封藏之本，一个气之本，一个仓廪之本，这四个本都是谈的生命过程中最重要的生理问题，怎么到了“罢极之本”突然讨论起疲劳的问题呢？这显然有悖逻辑。那么，这个罢极究竟谈的什么？首先我们还是看“极”，“极”是什么？前面说了，七首为一极，就是三万一千九百二十岁。到了极点这个时候，要发生“生数皆终，万物复始”的变化。可是谁能看到这个变化呢？谁能够活到三万一千九百二十岁呢？彭祖也不过八百岁。所以，要真实地看到这个极的变化是不可能的。但是，这个没关系，这并不妨碍我们认识它。因为我们可以利用《内经》的另一个思想武器来认识这个问题，这就是象。在《灵枢》经里，专门有一篇“顺气一日分为四时篇”，四时，就是春夏秋冬，它本是年周期里的四个时间单位，可是在《灵枢》的这一篇中，却把它放到了一天里面，认为一天里面也有春夏秋冬，为什么呢？这个就叫做“同象原理”。从象的角度看，春夏秋冬是怎么一回事呢？春夏秋冬就是生、长、收、藏，就是阳生阴长，阳杀阴藏。当然，在年这个周期里面，有生长收藏，但是，在日这个周期里有没有生长收藏呢？同样也有生长收藏。所以，岐伯曰：“朝则为春，日中为夏，日入为秋，夜半为冬。”虽然，年周期与日周期在时间长度上这个差别很大，但是，从象上而言，也就是从阴阳变化的角度而言，却没有什么差别。为什么“朝为春，日中为夏，日入为秋，夜半为冬”呢？因为朝则阳生，日中则阳长，日入则阳收，夜半则阳藏也。周期长度不同，但是，阴阳变化的这个象相同，这就是我们说的同象原理。以春生为例，在年周期里面，这个春生的长度是三个月，而在日周期里，春生的长度只有三个时辰，这就是它们的差别。同象原理建立以后，问题就好办了。我们知道在极这个周期里，存在一个“生数皆终，万物复始”的象变，那么，年的周期呢？我们看一看冬三月与春三月，冬三月，此谓闭藏，特别在北方，我们看到的是千里冰封，万里雪飘，万物凋零，生数皆终。而一旦度过了严冬，春天到来，则又是一派万物复始的发陈景象。这个闭藏的生数皆终与这个发陈的万物复始，不就是一个极变吗？所以，在年这个周期上，同样存在一个极的象变。年与年之间交替，实际上也是极与极之间的交替，这与一日之中亦见四时是一个道理。我们之所以能从这一年跨越到另一年，必须是作为这一年的这个“极”终结，罢了，另外一个“极”才能开始。所以，“罢极”的意义就在这里，它是促使年与年、岁与岁之间交替变换，也可以说是极与极之间交替变换的一个关键因素。如庚辰年转到辛巳年，马上就由金运太过转到了水运不及，这个跨越太大了。作为人体，我们怎么样保证在这个大跨度上与天地的变化保持一致，这就要靠厥阴，这就要靠肝，这就要靠这个“罢极之本”。在岁与岁这个层次上与天地沟通，这个要靠“罢极之本”，要靠厥阴；在气与气这个层次上与天地沟通则要靠“气之本”，要靠阳明。就像我们现在的收音机，收音机收到节目的一个前提，就是要使接收的频率与发射的频率相一致，这就需要频率调节器。通常调节器有两个，一个是粗调，一个是微调。厥阴是粗调，阳明是微调。有了粗，有了微，这就在多层次、全方位上与天地建立了相应关系。有这样一些专门的机制，有这样一些专门的部门来负责，人与四时相应就有了保证。可见中医理论的建立，不是一个随随便便的过程，她很严密，有理论，有实证，不是想当然。
二、阴阳的离合机制
以上我们讨论了三阴三阳引入厥阴、阳明的意义，三阴三阳建立起来后，中医的基本模型便随之确定。所以，到了《素问》的第六篇，就专门有一个“阴阳离合论”。怎么叫“阴阳离合”呢？首先从“合”的角度讲，合就是从综合来看，从总体来看，它谈的是很基本的层面，这个层面就是一阴一阳。阴阳的这个合的层面，在易系统里又叫做“道”，故《易·系辞》里面说：“一阴一阳之谓道。”我们前面讲的阳生阴长，阳杀阴藏，就主要是从合的这个层面谈。那么离呢？离就是分开来讲，《素问》里面谈到阴阳的无限可分性：“阴阳者，数之可十，推之可百，数之可千，推之可万，万之大不可胜数。”如果这样来分，那我们怎么能把握？所以，谈阴阳的离，我们不需这样来分，分成三就行了。阴分为三，阳分为三，这就是三阴三阳。用道家的说法，这叫做“一气含三造化功”。因此，阴阳的离合实际上就是谈一个分工合作的问题。合作就是要实现第二章所谈的阴阳的生长收藏，阳气的释放和蓄积，而要实现这样一个过程，就必须有不同的作用机制，这就要牵涉到分工，这也是《素问·阴阳离合论》最关注的一个问题。
1.门户概念的引入
《素问·阴阳离合论》在具体论述阴阳的离合时说：“是故三阳之离合也，太阳为开，阳明为合，少阳为枢。是故三阴之离合也，太阴为开，厥阴为合，少阴为枢。”一个开，一个合，一个枢，这是针对什么而言呢？很显然，它是针对门户而言。门户的作用大家都非常熟悉，就是要有开合，开则能够出入，合则出入停止。那么，门要能够开合，它靠什么起作用？它靠枢的作用。所以，门户这样一个总和的概念，要是把它分开来，就是开合枢这三部分。没有开合，门户就不成其为门户，而要实现开合自如，没有枢又不行。前面我们说了，天地阴阳的变化，无外乎就是一个升降出入的变化，故《素问·六微旨大论》说：“升降出入，无器不有。”有升降出入，当然就有生长收藏。那么，怎么个升降出入呢？古人在这个问题上动了很大脑筋。设想如果没有一个门户，一个理想中的门户在把持，这个出入的变化怎么进行呢？什么时候出，什么时候入，从什么地方出，从什么地方入？它总要通过一个地方。因此，在理论上，就有了一个门户概念的产生。有了门户的概念，我们认识阴阳的升降变化，阴阳的出入变化就方便多了。《素问·四气调神大论》曰：“夫四时阴阳者，万物之根本也，所以圣人春夏养阳，秋冬养阴，以从其根，故与万物沉浮于生长之门。”大家看，门户的概念就这样在《内经》系统里构建出来。这里的沉浮也就是讲出入，也就是讲升降。沉者入也，浮者出也。一方面是浮于生长之门，这个过程是讲阳气的出，阳气的升，实际上就是阳的释放；另一方面是沉于生长之门，这个过程是讲阳气的入，阳气的降，实际上就是阳的收藏蓄积。这里为什么要讲“与万物沉浮”呢？很清楚，就是要说明万物的这个沉浮，实际上就是阴阳的沉浮。万物的沉浮是表象，而它的实质，它的根本是阴阳在起变化。所以，我们观察任何事物，我们望、闻、问、切的目的，就是要透过这个表象，看它的实质，看它的根本，看它的这个阴阳变化。《内经》讲：“察色按脉，先别阴阳。”就是强调这个问题。毛泽东主席在一首诗中写道：“问苍茫大地，谁主沉浮？”如果把它借用到这里，那么肯定是阴阳主沉浮。门户的概念建立了，就必须有一个与之相应的工作机制，这就是上述的开合枢。具体地说，三阳有一个三阳的开合枢，三阴有一个三阴的开合枢。这就意味着应该有两个门，一个是三阳主宰的阳门，一个是三阴主宰的阴门。上面讲到的只是生长之门，其实这是一个省略，应该还有一个收藏之门。三阳主的阳门实际就是生长之门，三阴主的阴门，实际就是收藏之门。阳门打开了，生长之门打开了，阳气便不断升发，不断释放，随着这个升发，释放，自然界表现的便是春夏的变化，万物在这个过程逐渐地升浮起来。而随着阴门的打开，收藏之门的打开，阳气转到入降，转到蓄藏，这个时候秋冬开始了，万物则在这个过程中逐渐地消沉下去。上述两个门的分工虽然不同，但是，却要非常协调地工作。这里也体现了一个离合的思想。阳门开的时候，阴门要逐渐关闭，否则，阳气一边出，一边入，甚至出不敷入，那这个春夏的变化，这个生长的变化，就没有办法实现。同理，阴门开的时候，阳门也要逐渐的关闭，否则，阳气一边入，一边出，甚至入不敷出，那这个秋冬的变化，这个收藏的变化就根本没有办法实现。所以，为什么阴阳要强调协调统一，不能搞对立呢？如果你开你的我开我的，那整个升降出入就要搞乱。《素问·六微旨大论》说：“出入废则神机化灭，升降息则气立孤危。”神机化灭了，气立孤危了，那还有什么生命可言。所以，这是一个十分严重的问题。《伤寒论》讲六经，讲三阴三阳，实际上就是讲上面这两个门。两个门要协调好，必须三阴三阳的开合枢协调好，开合枢协调好了，阴阳的升降出入就不会有异常，升降出入没有异常，神机气立没有异常，这个生命就不会发生异常。我们从这个层面切入，不但整个《伤寒论》会很清楚，整个中医也会很清楚。下面就具体讨论这个问题。
2.阴阳的开合枢
（1）三阳之开合枢
《易经》这个系统在讨论两仪和四象之后，就跳跃到八卦这个层面。当然，八卦中也包含三阴和三阳，但是，阐述的角度显然与医学有很大的差别。所以，医学系统中的三阴三阳应该说是很独特的。我们看《素问》，在《素问》的前几篇里，只讲二阴和二阳，特别是《四气调神大论》，它只提少阳、少阴、太阳、太阴，直到第六篇《阴阳离合论》才明确提出三阴三阳。就是在二阴二阳的基础上增加一个厥阴和一个阳明。阴阳这个概念在传统文化的各个领域都能找到，可以说各行各业都在用它，但是，像厥阴、阳明这样一对概念，则几乎只限于医家之用。可见这两个概念对中医的关系很大。什么叫阳明？什么叫厥阴呢？《素问》里面有专门的定义：两阳相合为阳明，两阴交尽为厥阴。而其他的二阴二阳，《素问》里没有专门的定义。这就说明了厥阴和阳明的引入，对于中医理论的构建具有非常特殊的意义。中医有一个最基本的观念，或者说最基本的特点，这个观念我们前面已经提到过，就是整体观念，天人合一。这样一个观念，实际上我们在传统文化的各个领域都能见到，儒家的学问，道家的学问，都是秉承这样一个基本的东西。可以说，这个观念是整个传统文化大厦的基石。前面我们讨论伤寒的时候，引述了许多《四气调神大论》的观点，实际上都是说的这个观念。前章已经说过，春夏为什么要养阳？秋冬为什么要养阴？春为什么要养生？夏为什么要养长？为的是与天地同步。天地生你也生，天地怎么变化，你也怎么变化，这就是天人相应，这就是整体观念，这就是道！得道多助，失道寡助；顺天者昌，逆天者亡，从原始自然的意义讲，就是说的这个问题。那么，我们要跟上天地的变化，首先必须知道天地怎样变化。天地变化的最明显的单位，或者说最明显的层次就是年。每一年天地都要作一个很大的变化，比如今年庚辰年，变到明年就是辛巳年。庚辰年是金运太过，太阳寒水司天，太阴湿土在泉，而辛巳年就变成了水运不及，厥阴风木司天，少阳相火在泉。一个金运、一个水运，一个太过，一个不及，这个变化太大了。在年这样一个大变化的框架里，还有一个更基本、更细小的变化单位，这就是气。气这个概念我们在第一章里已经讨论过，它本来是岐伯保密的东西，但是，在黄帝的追问下，不得不说出来。一年由二十四个气组成，在年这个框架里，气就是最基本的变化单位，天地便是按照这样一个单位在不断地变化。由小雪到大雪，由小寒到大寒。人要与天地相应，就必须得跟上这个变化。天地交换到另一个气的时候，你也要跟上来，还停在原来的这个气上，这就叫做“不及”。如果天地还没有跨越到另外一个气上，你先走了，这叫“太过”。太过与不及都没有与天地保持一致，没有与天地相应。那么，在气这个层次上，人体靠什么来与天地自然保持一致呢？就靠肺。《素问·灵兰秘典论》、《素问·六节藏象论》讲“肺者，治节出焉”，“肺者，气之本”。实际上就是揭示肺的这个功能。有关这个问题，我们在第一章已专门地分析过，肺在运气里，在《阴阳大论》里，它属于阳明。阳明燥金，主肺与大肠。所以，阳明这个概念的引入，对于在气这个层次上建立天人合一的专门机制是非常重要的。阳明为着沟通气这个层次的天人关系，那么，厥阴呢？厥阴为风木，主肝胆。《素问·六节藏象论》云：“肝者，罢极之本，魂之居也。”罢极是什么意思呢？按照前人的很多说法，包括现代《中基》教材的说法，都认为这个罢极是当“疲极”讲，疲劳到了极限，这个说法我们认为不符合逻辑。为什么呢？因为《六节藏象论》这一篇都是探讨藏府的正常功能，一个生之本，一个封藏之本，一个气之本，一个仓廪之本，这四个本都是谈的生命过程中最重要的生理问题，怎么到了“罢极之本”突然讨论起疲劳的问题呢？这显然有悖逻辑。那么，这个罢极究竟谈的什么？首先我们还是看“极”，“极”是什么？前面说了，七首为一极，就是三万一千九百二十岁。到了极点这个时候，要发生“生数皆终，万物复始”的变化。可是谁能看到这个变化呢？谁能够活到三万一千九百二十岁呢？彭祖也不过八百岁。所以，要真实地看到这个极的变化是不可能的。但是，这个没关系，这并不妨碍我们认识它。因为我们可以利用《内经》的另一个思想武器来认识这个问题，这就是象。在《灵枢》经里，专门有一篇“顺气一日分为四时篇”，四时，就是春夏秋冬，它本是年周期里的四个时间单位，可是在《灵枢》的这一篇中，却把它放到了一天里面，认为一天里面也有春夏秋冬，为什么呢？这个就叫做“同象原理”。从象的角度看，春夏秋冬是怎么一回事呢？春夏秋冬就是生、长、收、藏，就是阳生阴长，阳杀阴藏。当然，在年这个周期里面，有生长收藏，但是，在日这个周期里有没有生长收藏呢？同样也有生长收藏。所以，岐伯曰：“朝则为春，日中为夏，日入为秋，夜半为冬。”虽然，年周期与日周期在时间长度上这个差别很大，但是，从象上而言，也就是从阴阳变化的角度而言，却没有什么差别。为什么“朝为春，日中为夏，日入为秋，夜半为冬”呢？因为朝则阳生，日中则阳长，日入则阳收，夜半则阳藏也。周期长度不同，但是，阴阳变化的这个象相同，这就是我们说的同象原理。以春生为例，在年周期里面，这个春生的长度是三个月，而在日周期里，春生的长度只有三个时辰，这就是它们的差别。同象原理建立以后，问题就好办了。我们知道在极这个周期里，存在一个“生数皆终，万物复始”的象变，那么，年的周期呢？我们看一看冬三月与春三月，冬三月，此谓闭藏，特别在北方，我们看到的是千里冰封，万里雪飘，万物凋零，生数皆终。而一旦度过了严冬，春天到来，则又是一派万物复始的发陈景象。这个闭藏的生数皆终与这个发陈的万物复始，不就是一个极变吗？所以，在年这个周期上，同样存在一个极的象变。年与年之间交替，实际上也是极与极之间的交替，这与一日之中亦见四时是一个道理。我们之所以能从这一年跨越到另一年，必须是作为这一年的这个“极”终结，罢了，另外一个“极”才能开始。所以，“罢极”的意义就在这里，它是促使年与年、岁与岁之间交替变换，也可以说是极与极之间交替变换的一个关键因素。如庚辰年转到辛巳年，马上就由金运太过转到了水运不及，这个跨越太大了。作为人体，我们怎么样保证在这个大跨度上与天地的变化保持一致，这就要靠厥阴，这就要靠肝，这就要靠这个“罢极之本”。在岁与岁这个层次上与天地沟通，这个要靠“罢极之本”，要靠厥阴；在气与气这个层次上与天地沟通则要靠“气之本”，要靠阳明。就像我们现在的收音机，收音机收到节目的一个前提，就是要使接收的频率与发射的频率相一致，这就需要频率调节器。通常调节器有两个，一个是粗调，一个是微调。厥阴是粗调，阳明是微调。有了粗，有了微，这就在多层次、全方位上与天地建立了相应关系。有这样一些专门的机制，有这样一些专门的部门来负责，人与四时相应就有了保证。可见中医理论的建立，不是一个随随便便的过程，她很严密，有理论，有实证，不是想当然。
二、阴阳的离合机制
以上我们讨论了三阴三阳引入厥阴、阳明的意义，三阴三阳建立起来后，中医的基本模型便随之确定。所以，到了《素问》的第六篇，就专门有一个“阴阳离合论”。怎么叫“阴阳离合”呢？首先从“合”的角度讲，合就是从综合来看，从总体来看，它谈的是很基本的层面，这个层面就是一阴一阳。阴阳的这个合的层面，在易系统里又叫做“道”，故《易·系辞》里面说：“一阴一阳之谓道。”我们前面讲的阳生阴长，阳杀阴藏，就主要是从合的这个层面谈。那么离呢？离就是分开来讲，《素问》里面谈到阴阳的无限可分性：“阴阳者，数之可十，推之可百，数之可千，推之可万，万之大不可胜数。”如果这样来分，那我们怎么能把握？所以，谈阴阳的离，我们不需这样来分，分成三就行了。阴分为三，阳分为三，这就是三阴三阳。用道家的说法，这叫做“一气含三造化功”。因此，阴阳的离合实际上就是谈一个分工合作的问题。合作就是要实现第二章所谈的阴阳的生长收藏，阳气的释放和蓄积，而要实现这样一个过程，就必须有不同的作用机制，这就要牵涉到分工，这也是《素问·阴阳离合论》最关注的一个问题。
1.门户概念的引入
《素问·阴阳离合论》在具体论述阴阳的离合时说：“是故三阳之离合也，太阳为开，阳明为合，少阳为枢。是故三阴之离合也，太阴为开，厥阴为合，少阴为枢。”一个开，一个合，一个枢，这是针对什么而言呢？很显然，它是针对门户而言。门户的作用大家都非常熟悉，就是要有开合，开则能够出入，合则出入停止。那么，门要能够开合，它靠什么起作用？它靠枢的作用。所以，门户这样一个总和的概念，要是把它分开来，就是开合枢这三部分。没有开合，门户就不成其为门户，而要实现开合自如，没有枢又不行。前面我们说了，天地阴阳的变化，无外乎就是一个升降出入的变化，故《素问·六微旨大论》说：“升降出入，无器不有。”有升降出入，当然就有生长收藏。那么，怎么个升降出入呢？古人在这个问题上动了很大脑筋。设想如果没有一个门户，一个理想中的门户在把持，这个出入的变化怎么进行呢？什么时候出，什么时候入，从什么地方出，从什么地方入？它总要通过一个地方。因此，在理论上，就有了一个门户概念的产生。有了门户的概念，我们认识阴阳的升降变化，阴阳的出入变化就方便多了。《素问·四气调神大论》曰：“夫四时阴阳者，万物之根本也，所以圣人春夏养阳，秋冬养阴，以从其根，故与万物沉浮于生长之门。”大家看，门户的概念就这样在《内经》系统里构建出来。这里的沉浮也就是讲出入，也就是讲升降。沉者入也，浮者出也。一方面是浮于生长之门，这个过程是讲阳气的出，阳气的升，实际上就是阳的释放；另一方面是沉于生长之门，这个过程是讲阳气的入，阳气的降，实际上就是阳的收藏蓄积。这里为什么要讲“与万物沉浮”呢？很清楚，就是要说明万物的这个沉浮，实际上就是阴阳的沉浮。万物的沉浮是表象，而它的实质，它的根本是阴阳在起变化。所以，我们观察任何事物，我们望、闻、问、切的目的，就是要透过这个表象，看它的实质，看它的根本，看它的这个阴阳变化。《内经》讲：“察色按脉，先别阴阳。”就是强调这个问题。毛泽东主席在一首诗中写道：“问苍茫大地，谁主沉浮？”如果把它借用到这里，那么肯定是阴阳主沉浮。门户的概念建立了，就必须有一个与之相应的工作机制，这就是上述的开合枢。具体地说，三阳有一个三阳的开合枢，三阴有一个三阴的开合枢。这就意味着应该有两个门，一个是三阳主宰的阳门，一个是三阴主宰的阴门。上面讲到的只是生长之门，其实这是一个省略，应该还有一个收藏之门。三阳主的阳门实际就是生长之门，三阴主的阴门，实际就是收藏之门。阳门打开了，生长之门打开了，阳气便不断升发，不断释放，随着这个升发，释放，自然界表现的便是春夏的变化，万物在这个过程逐渐地升浮起来。而随着阴门的打开，收藏之门的打开，阳气转到入降，转到蓄藏，这个时候秋冬开始了，万物则在这个过程中逐渐地消沉下去。上述两个门的分工虽然不同，但是，却要非常协调地工作。这里也体现了一个离合的思想。阳门开的时候，阴门要逐渐关闭，否则，阳气一边出，一边入，甚至出不敷入，那这个春夏的变化，这个生长的变化，就没有办法实现。同理，阴门开的时候，阳门也要逐渐的关闭，否则，阳气一边入，一边出，甚至入不敷出，那这个秋冬的变化，这个收藏的变化就根本没有办法实现。所以，为什么阴阳要强调协调统一，不能搞对立呢？如果你开你的我开我的，那整个升降出入就要搞乱。《素问·六微旨大论》说：“出入废则神机化灭，升降息则气立孤危。”神机化灭了，气立孤危了，那还有什么生命可言。所以，这是一个十分严重的问题。《伤寒论》讲六经，讲三阴三阳，实际上就是讲上面这两个门。两个门要协调好，必须三阴三阳的开合枢协调好，开合枢协调好了，阴阳的升降出入就不会有异常，升降出入没有异常，神机气立没有异常，这个生命就不会发生异常。我们从这个层面切入，不但整个《伤寒论》会很清楚，整个中医也会很清楚。下面就具体讨论这个问题。
2.阴阳的开合枢
（1）三阳之开合枢
The system of the *Yijing* (Book of Changes) jumps to the level of the Eight Trigrams after discussing the Two Modes (Liangyi) and Four Symbols (Sixiang). Of course, the Eight Trigrams also contain Three Yin and Three Yang, but the perspective of exposition is clearly quite different from that in medicine. Therefore, the Three Yin and Three Yang in the medical system can be said to be very unique. Looking at the *Suwen* (Basic Questions), in the first few chapters of the *Suwen*, only Two Yin and Two Yang are discussed. Specifically, in the chapter "Si Qi Tiao Shen Da Lun" (Great Discourse on Regulating the Spirit According to the Four Seasons), it only mentions Shaoyang (Lesser Yang), Shaoyin (Lesser Yin), Taiyang (Greater Yang), and Taiyin (Greater Yin). It is not until the sixth chapter, "Yin Yang Li He Lun" (Discourse on the Separation and Combination of Yin and Yang), that Three Yin and Three Yang are explicitly proposed. This involves adding Jueyin (Terminal Yin) and Yangming (Bright Yang) to the basis of Two Yin and Two Yang. The concept of Yin and Yang can be found in various fields of traditional culture; one could say that all trades and professions use it. However, a pair of concepts like Jueyin and Yangming is almost exclusively used by medical practitioners. This shows that these two concepts have a great relationship with Traditional Chinese Medicine (TCM). What is meant by Yangming? What is meant by Jueyin? The *Suwen* provides specific definitions: "When two Yangs combine, it is called Yangming; when two Yins intersect and end, it is called Jueyin." There are no specific definitions for the other Two Yin and Two Yang in the *Suwen*. This illustrates that the introduction of Jueyin and Yangming has a very special significance for the construction of TCM theory. TCM has a most basic concept, or perhaps its most basic characteristic, which we have mentioned before: the holistic concept (Holistic View) and the unity of heaven and humanity (Tian Ren He Yi). We can actually see such a concept in various fields of traditional culture. The learning of Confucianism and Daoism both uphold this basic principle. One could say that this concept is the cornerstone of the entire edifice of traditional culture. When we discussed Shanghan (Cold Damage) earlier, we cited many viewpoints from "Si Qi Tiao Shen Da Lun," which essentially referred to this concept. As stated in the previous chapter, why nourish Yang in spring and summer? Why nourish Yin in autumn and winter? Why nurture life in spring? Why foster growth in summer? It is to synchronize with heaven and earth. Heaven and earth generate, so you generate; heaven and earth change, so you change. This is Tian Ren Xiang Ying (Heaven-Human Resonance), this is the holistic concept, this is the Dao! He who obtains the Dao has much support; he who loses the Dao has little support; those who follow heaven prosper, those who defy heaven perish. In the original natural sense, this refers to this issue. Then, to keep up with the changes of heaven and earth, we must first know how heaven and earth change. The most obvious unit, or the most obvious level, of heaven and earth's change is the year. Every year, heaven and earth undergo a significant change. For example, if this year is the Gengchen year, next year will be the Xinsi year. The Gengchen year features excessive Metal Transport (Jin Yun Tai Guo), with Taiyang Cold Water ruling the Heaven (Si Tian) and Taiyin Damp Earth ruling the Earth (Zai Quan). The Xinsi year becomes deficient Water Transport (Shui Yun Bu Ji), with Jueyin Wind Wood ruling the Heaven and Shaoyang Ministerial Fire ruling the Earth. One Metal Transport, one Water Transport; one excessive, one deficient. This change is too great. Within the framework of such a large-scale annual change, there is an even more fundamental and finer unit of change, which is Qi (Vital Energy). We discussed the concept of Qi in Chapter 1. It was originally something kept secret by Qibo, but under Huangdi's persistent questioning, he had to reveal it. A year consists of twenty-four Qi segments. Within the framework of the year, Qi is the most basic unit of change, and heaven and earth constantly change according to this unit. From Minor Snow to Major Snow, from Minor Cold to Major Cold. To resonate with heaven and earth, humans must keep up with this change. When heaven and earth switch to another Qi segment, you must also follow; if you remain stuck at the original Qi segment, this is called "deficiency" (Bu Ji). If heaven and earth have not yet crossed to another Qi segment, but you move ahead first, this is called "excess" (Tai Guo). Both excess and deficiency fail to maintain consistency with heaven and earth, failing to resonate with them. So, at the level of Qi, what does the human body rely on to maintain consistency with nature? It relies on the Lung. The *Suwen·Ling Lan Mi Dian Lun* and *Suwen·Liu Jie Zang Xiang Lun* state: "The Lung is where governance and regulation emerge" and "The Lung is the root of Qi." This actually reveals this function of the Lung. Regarding this issue, we analyzed it specifically in Chapter 1. In the context of Five Movements and Six Qi, in the "Yin Yang Da Lun," the Lung belongs to Yangming. Yangming Dryness Metal governs the Lung and Large Intestine. Therefore, the introduction of the concept of Yangming is of vital importance for establishing a specialized mechanism of the unity of heaven and humanity at the level of Qi. If Yangming serves to communicate the heaven-human relationship at the level of Qi, then what about Jueyin? Jueyin is Wind Wood, governing the Liver and Gallbladder. The *Suwen·Liu Jie Zang Xiang Lun* says: "The Liver is the root of fatigue/exhaustion (Ba Ji) and the residence of the Hun (Ethereal Soul)." What does "Ba Ji" mean? According to many interpretations by predecessors, including modern textbooks on Basic Theory of TCM, "Ba Ji" is interpreted as "Pi Ji" (extreme fatigue). We believe this interpretation is illogical. Why? Because the chapter "Liu Jie Zang Xiang Lun" explores the normal functions of the Zang organs. The Root of Life, the Root of Storage, the Root of Qi, and the Root of Granaries—these four roots discuss the most important physiological issues in the life process. How can it suddenly discuss fatigue at the "Root of Fatigue"? This obviously contradicts logic. So, what does "Ba Ji" actually refer to? First, let us look at "Ji" (Extremity/Pole). What is "Ji"? As mentioned earlier, seven cycles constitute one "Ji," which amounts to 31,920 years. At this extremity, a change occurs where "all generative numbers end, and all things restart." But who can see this change? Who can live to 31,920 years? Peng Zu lived only 800 years. Therefore, it is impossible to truly observe the change of this "Ji." However, this does not hinder our understanding of it. Because we can utilize another intellectual weapon from the *Neijing* to understand this problem: Xiang (Image/Symbol). In the *Ling Shu*, there is a specific chapter titled "Shun Qi Yi Ri Fen Wei Si Shi Pian" (Discourse on Dividing One Day into Four Seasons According to Qi Flow). The Four Seasons refer to Spring, Summer, Autumn, and Winter. Originally, these were four time units within the annual cycle, but in this chapter of the *Ling Shu*, they are placed within a single day, asserting that there are also Spring, Summer, Autumn, and Winter within a day. Why? This is called the "Principle of Homologous Images" (Tong Xiang Yuan Li). From the perspective of Xiang, what are Spring, Summer, Autumn, and Winter? They are Growth, Flourishing, Harvesting, and Storage; they are Yang generating and Yin growing, Yang killing and Yin storing. Of course, within the annual cycle, there is growth, flourishing, harvesting, and storage. But is there growth, flourishing, harvesting, and storage within the daily cycle? Similarly, there is. Thus, Qibo said: "Morning is Spring, noon is Summer, sunset is Autumn, and midnight is Winter." Although the difference in time length between the annual cycle and the daily cycle is huge, from the perspective of Xiang, or rather from the angle of Yin-Yang change, there is no difference. Why is "morning Spring, noon Summer, sunset Autumn, midnight Winter"? Because morning sees Yang generating, noon sees Yang growing, sunset sees Yang harvesting, and midnight sees Yang storing. The cycle lengths differ, but the Xiang of Yin-Yang change is identical. This is the Principle of Homologous Images we mentioned. Taking Spring Growth as an example, in the annual cycle, the duration of Spring Growth is three months, whereas in the daily cycle, the duration of Spring Growth is only three double-hours (Shichen). This is their difference. Once the Principle of Homologous Images is established, problems become easier to handle. We know that within the cycle of "Ji," there exists a transformation of images where "all generative numbers end, and all things restart." What about the annual cycle? Let us look at the three winter months versus the three spring months. The three winter months are called "Closing and Storing." Especially in the north, we see ice covering thousands of miles and snow drifting for ten thousand miles; all things wither, and generative numbers end. Once the severe winter passes and spring arrives, it presents a scene of all things restarting and sprouting. Is this ending of generative numbers through closing/storing and the restarting of all things through sprouting not a transformation of "Ji"? Therefore, on the annual cycle, there similarly exists a transformation of the image of "Ji." The alternation between years is actually the alternation between "Jis," which is the same principle as seeing the Four Seasons within a single day. The reason we can cross from one year to another is that the "Ji" of this year must end and cease, allowing another "Ji" to begin. Thus, the meaning of "Ba Ji" lies here. It is a key factor promoting the alternation between years and ages, or alternatively, the alternation between "Jis." For instance, when the Gengchen year transitions to the Xinsi year, it immediately shifts from excessive Metal Transport to deficient Water Transport. This leap is too large. As humans, how do we ensure consistency with heavenly and earthly changes during this large span? This relies on Jueyin, this relies on the Liver, and this relies on this "Root of Ba Ji." To communicate with heaven and earth at the level of years, we rely on the "Root of Ba Ji" and Jueyin; to communicate with heaven and earth at the level of Qi, we rely on the "Root of Qi" and Yangming. It is like our current radios. A prerequisite for a radio to receive a program is that the receiving frequency must match the transmitting frequency, which requires a frequency tuner. Usually, there are two tuners: coarse adjustment and fine adjustment. Jueyin is the coarse adjustment, and Yangming is the fine adjustment. With coarse and fine adjustments, a corresponding relationship with heaven and earth is established across multiple levels and comprehensively. With such specialized mechanisms and departments responsible for them, the resonance of humans with the Four Seasons is guaranteed. It is evident that the establishment of TCM theory is not a casual process; it is rigorous, possessing both theory and empirical evidence, not mere speculation.
II. The Mechanism of Separation and Combination of Yin and Yang
Above, we discussed the significance of introducing Jueyin and Yangming into the Three Yin and Three Yang. After the establishment of the Three Yin and Three Yang, the basic model of TCM was thereby determined. Therefore, in the sixth chapter of the *Suwen*, there is a dedicated "Yin Yang Li He Lun" (Discourse on the Separation and Combination of Yin and Yang). What is called "Separation and Combination of Yin and Yang"? First, speaking from the perspective of "Combination" (He), combination means looking at it comprehensively and generally. It discusses a very basic level, which is one Yin and one Yang. This level of combination of Yin and Yang is also called the "Dao" in the system of the *Yijing*. Hence, the *Yijing·Xi Ci* states: "One Yin and one Yang is called the Dao." The Yang generating and Yin growing, Yang killing and Yin storing that we discussed earlier are mainly talked about from this level of combination. Then, what about "Separation" (Li)? Separation means discussing them separately. The *Suwen* discusses the infinite divisibility of Yin and Yang: "Yin and Yang, when counted, can reach ten; when extended, can reach a hundred; when counted further, can reach a thousand; when extended further, can reach ten thousand. Beyond ten thousand, the number cannot be fully counted." If divided in this manner, how can we grasp it? Therefore, when discussing the separation of Yin and Yang, we do not need to divide it this way; dividing it into three is sufficient. Yin is divided into three, and Yang is divided into three. This is the Three Yin and Three Yang. Using Daoist terminology, this is called "One Qi contains the creative work of three transformations." Therefore, the separation and combination of Yin and Yang essentially discusses the issue of division of labor and cooperation. Cooperation aims to realize the growth, flourishing, harvesting, and storage of Yin and Yang, and the release and accumulation of Yang Qi discussed in Chapter 2. To realize such a process, different mechanisms of action are required, which involves division of labor. This is also the primary concern of the *Suwen·Yin Yang Li He Lun*.
1. The Introduction of the Concept of Gate/Portal
In the specific discussion of the separation and combination of Yin and Yang, the *Suwen·Yin Yang Li He Lun* states: "Thus, the separation and combination of the Three Yangs: Taiyang is Opening, Yangming is Closing, Shaoyang is Pivot. Thus, the separation and combination of the Three Yins: Taiyin is Opening, Jueyin is Closing, Shaoyin is Pivot." An Opening, a Closing, and a Pivot—what is this addressing? Obviously, it addresses the gate/portal. Everyone is very familiar with the function of a gate/portal: it must have opening and closing. Opening allows entry and exit; closing stops entry and exit. So, what enables a door to open and close? It relies on the function of the pivot. Therefore, if we break down the total concept of a gate/portal, it consists of these three parts: Opening, Closing, and Pivot. Without opening and closing, a gate/portal ceases to be a gate/portal; and to achieve free opening and closing, without a pivot is impossible. As mentioned earlier, the changes of heaven and earth Yin and Yang are nothing more than changes of ascending, descending, exiting, and entering. Thus, the *Suwen·Liu Wei Zhi Da Lun* states: "Ascending, descending, exiting, and entering exist in every vessel/organ." With ascending, descending, exiting, and entering, there naturally follows growth, flourishing, harvesting, and storage. So, how do these ascending, descending, exiting, and entering occur? The ancients put great thought into this issue. Suppose there were no gate/portal, and an ideal gate/portal did not control it, how would these changes of entry and exit proceed? When to exit, when to enter, from where to exit, from where to enter? It must always pass through a certain place. Therefore, theoretically, the concept of a gate/portal arose. With the concept of a gate/portal, our understanding of the ascending/descending changes and exiting/entering changes of Yin and Yang becomes much more convenient. The *Suwen·Si Qi Tiao Shen Da Lun* says: "The Yin and Yang of the Four Seasons are the root of all things. Therefore, the sages nourish Yang in spring and summer, and nourish Yin in autumn and winter, to follow their root, thus floating and sinking with all things in the gate of growth." Everyone see, the concept of a gate/portal is constructed within the *Neijing* system here. Here, floating and sinking refer to exiting and entering, which also refers to ascending and descending. Sinking is entering; floating is exiting. On one hand, floating in the gate of growth refers to the exiting and ascending of Yang Qi, which is essentially the release of Yang; on the other hand, sinking in the gate of growth refers to the entering and descending of Yang Qi, which is essentially the storage and accumulation of Yang. Why mention "floating and sinking with all things" here? Clearly, it is to explain that the floating and sinking of all things is actually the floating and sinking of Yin and Yang. The floating and sinking of all things is the appearance, while its substance and root lie in the changes of Yin and Yang. Therefore, when observing any thing, the purpose of Observation (Wang), Listening/Smelling (Wen), Inquiry (Wen), and Palpation (Qie) is to penetrate this appearance to see its substance, its root, and its Yin-Yang changes. The *Neijing* states: "Examine colors and press pulses, first distinguish Yin and Yang." This emphasizes this issue. Chairman Mao Zedong wrote in a poem: "Ask the vast earth, who rules the floating and sinking?" If borrowed here, it would certainly be Yin and Yang that rule the floating and sinking. Once the concept of the gate/portal is established, a corresponding working mechanism is required, which is the aforementioned Opening-Closing-Pivot. Specifically, the Three Yangs have a Three Yangs' Opening-Closing-Pivot, and the Three Yins have a Three Yins' Opening-Closing-Pivot. This implies there should be two gates: one Yang Gate governed by the Three Yangs, and one Yin Gate governed by the Three Yins. What was mentioned above is only the Gate of Growth; actually, this is an omission. There should also be a Gate of Storage. The Yang Gate governed by the Three Yangs is actually the Gate of Growth, and the Yin Gate governed by the Three Yins is actually the Gate of Storage. When the Yang Gate opens, the Gate of Growth opens, and Yang Qi continuously ascends and releases. Along with this ascent and release, nature manifests the changes of spring and summer, and all things gradually float upwards in this process. And as the Yin Gate opens, the Gate of Storage opens, Yang Qi turns to entering and descending, turning to storage. At this time, autumn and winter begin, and all things gradually sink downwards in this process. Although the division of labor between the two gates mentioned above is different, they must work in very close coordination. This also embodies the idea of separation and combination. When the Yang Gate opens, the Yin Gate must gradually close; otherwise, if Yang Qi exits on one side and enters on the other, or even if exit exceeds input, the changes of spring and summer, the changes of growth, cannot be realized. Similarly, when the Yin Gate opens, the Yang Gate must also gradually close; otherwise, if Yang Qi enters on one side and exits on the other, or even if input exceeds exit, the changes of autumn and winter, the changes of storage, cannot be realized at all. So, why emphasize coordination and unity of Yin and Yang, and oppose opposition? If you open yours and I open mine, the entire ascending, descending, exiting, and entering will be chaotic. The *Suwen·Liu Wei Zhi Da Lun* says: "If exiting and ceasing, the Spirit Mechanism perishes; if ascending and descending stop, the Qi Establishment stands in peril." If the Spirit Mechanism perishes and the Qi Establishment stands in peril, what life is there to speak of? Therefore, this is a very serious issue. The *Shanghan Lun* discusses the Six Channels and the Three Yin and Three Yang, which essentially discusses these two gates mentioned above. To coordinate the two gates well, the Opening-Closing-Pivot of the Three Yin and Three Yang must be coordinated well. If the Opening-Closing-Pivot is coordinated well, the ascending, descending, exiting, and entering of Yin and Yang will not be abnormal. If ascending, descending, exiting, and entering are not abnormal, and the Spirit Mechanism and Qi Establishment are not abnormal, then life will not experience abnormalities. Cutting into this level, not only will the entire *Shanghan Lun* become clear, but the entire TCM will also become clear. Below, we will specifically discuss this issue.
2. The Opening, Closing, and Pivot of Yin and Yang