中医里最重要的东西是什么？中医里最核心的东西是什么？方方面面都要围绕它，离开它就不行的这个东西是什么？这就是阴阳！《素问·阴阳应象大论》的开首即说：“阴阳者，天地之道也，万物之纲纪，变化之父母，生杀之本始，神明之府也，治病必求于本。”《素问》的这段话对阴阳作了高度的浓缩和概括。我们做任何学问，尤其是中医这门学问，离不开天地，而阴阳是天地之道；阴阳是万物的纲纪，一个万物，一个纲纪，大家可以掂量一下这个分量，有什么东西还能逃过这个阴阳；它是变化的父母，我们探讨事物，无非是探讨它的变化，时间的变化，空间的变化，而是什么导致这个变化呢？是阴阳；我们接触社会，接触自然，社会的东西也好，自然的东西也好，不论你是动物还是植物，是有机物还是无机物，是宇宙还是银河，它的整个过程无非就是一个生生杀杀的过程，那么，这个生杀是怎么产生的呢？它的本始还是阴阳；另外，就是神明之府，神明就是讲精神讲思维，所以，这一条与人类自身的关系特别大，那么，神明怎么来，还是与阴阳有关；最后，就要谈到治病求本的问题，现在人都知道说：西医治标，中医治本。当我们问一句中医怎么治本？或者中医通过什么来治本呢？这就回答不上了。其实，这个本还是阴阳，还是要在阴阳里面寻求。阴阳就是这样一个关系到方方面面的，最本始的东西。不知大家对阴阳有一个什么样的认识？是否达到了《内经》的高度？我在教授本科生和研究生时都喜欢提这个问题，而同学们给我的回答也就是《中基》教材的那几条，什么对立制约，互根互用，消长平衡，相互转化等等。而再往下问，答不出了。学阴阳，光懂这些还不够。怎么个对立，怎么个互根互用，这些你都要有真实的感受。对于任何事物的变化，你都能落实到阴阳上面，甚至一举手、一投足你都能分辨出阴阳来，都能感受出阴阳来，只有这样，阴阳才能为你所用，你也才能用阴阳解决真正的实际问题
（1）阴阳的关系
阴阳谈的是阴与阳两者之间的事，既然是两者，就有一个相互的关系问题，这也是阴阳这门学问里最重要的一个问题。上述这个关系，《素问·阴阳应象大论》里有很精辟的论述，就是“阳生阴长，阳杀阴藏”。这句话基本上将阴阳的主要方面包含进去了，因此，只要弄通了它，阴阳的学问也就可以基本解决。“阳生阴长，阳杀阴藏”主要是讲的一年里的阴阳变化以及万物的生长情况。阳生阴长主要讲上半年，也就是春夏的变化。在这个过程中，阳渐渐生，阴渐渐长，两者的关系非常协调。联系到具体的自然，春日以后，白日渐长，气温渐高，我们随处可以感受到阳气的不断增长。那么阴呢？阳化气，阴成形，这些成形的，属阴的万物也随着这个阳的增长而不断地繁茂，真正的一派欣欣向荣。这个过程真正是阳在生，阴在长，夫唱妇随。与我们以往所说的对立的、消长的关系好像不同，并不是阳产生了，万物反而消灭，完全不是这么一个情况。如果用现代一些的语言来形容这个过程，那么，阳气就好比能量，我们可以设想在天地之间有这样一个能量库，而在春夏这两季，能量是处在一个释放的过程，随着能量的释放，万物得到这个能量的供给，便逐渐的生长，繁茂起来。否则，万物凭什么会生长繁茂呢？就是因为这个阳气的释放，这个能量的释放造成的。这是阳生阴长。那么，阳杀阴藏呢？这是讲秋冬的变化。大家不要把这个“阳杀”看成真正的杀灭，“阳杀”与“阳生”是一个相对的概念。既然春夏的阳生指的是阳的释放，能量的释放。那这个释放是不是会无休止的进行下去呢？应该不会。这好比我们拳击，拳头伸展打出去了，如果拳头还老是停留在这个状态，那就没办法进行第二击。所以，必须先把拳头收回来，才能打下面的一击。阳气也是这样，老是生发，老是释放行不行？不行！这样就不能持续。所以，生发、释放到一定程度后，它就逐渐地转入到收藏，这个阳气的收藏相对于释放而言，就是“阳杀”。阳杀了，能量收藏起来了，天地万物得不到这个能量的供给，万物的生长就趋于停止，而且渐渐地凋零、枯萎，这就是我们看到的秋冬景象。所谓“秋风吹渭水，落叶满长安”就是讲的这个肃杀的状态，就是讲的这个收藏的状态。上述的这个过程是周而复始、如环无端的。所以，收藏到一定的程度后，又要开始新一轮的生发、释放。这便是《素问》所讲的“重阳必阴，重阴必阳”。阳指的是生发、释放的这个过程，阴指的是收藏的过程。春夏为阳，秋冬为阴指的也是这个过程。用《素问》的“重阳必阴，重阴必阳”来阐述上面的这个转换，是非常形象的。为了更好的理解这个过程，我们可以结合一些《周易》方面的知识。《周易》是一本专门讲阴阳变化的书，而且这个阴阳的变化它用一个二维的图象表示出来，这就使阴阳的变化更为直观、更为清晰。特别是描述一年的阴阳变化，它有专门的“十二消息卦”，即：复（聓）、临（耹）、泰（耺）、大壮（耼）、聎（耾）、乾（聀）、姤（聁）、遯（聄）、否（聅）、观（聇）、剥（聈）、坤（聉），如果用一句诗来记忆十二消息卦，就是“复临泰壮聎乾姤，遯否观剥坤二六。”其中复卦对应的是老历十一月的变化，依次类推，临为十二月，泰为正月，大壮为二月，聎为三月，乾为四月，姤为五月，遯为六月，否为七月，观为八月，剥为九月，坤为十月。上述的十二消息卦，在易系统里又叫别卦，它是由两个经卦重叠而成，经卦也就是我们常说的八卦系统，别卦也就是常说的六十四卦系统。从十二消息卦里，我们可以看到，除了乾坤两卦以外，其他的十个卦都是阴阳爻混杂在一起，既有阴，也有阳。而乾坤两卦不同，它是纯阴纯阳。乾卦由两个纯阳的经卦（乾）重叠而成，所以，又称重阳卦。坤卦由两个纯阴的经卦（坤）重叠而成，所以，又称重阴卦。从复卦开始我们可以看到，阳爻在逐渐增多，标志着阳气的生发、释放在不断地增强，一直到乾卦，变成六爻皆阳，变成重阳，阳的生发、释放也到了最大的程度。再往下去怎么样呢？重阳必阴。所以到了下一卦，到了姤卦的时候，上述这样一种阳的格局就起了根本的变化，阳不再增长了，而阴却悄然而起。姤卦所对应的月份是五月，而姤卦对应的这样一种重阳必阴的转换则发生在五月的夏至节上。“至”不是到来的意思，“至”的意思是极限。夏为阳，到夏至这个点上，阳的增长已经到了极限，而物极必反，所以就有这个“夏至—阴生”的变化，就有这个阳极生阴，重阳必阴的变化。姤卦以后，我们看到了另外一个截然不同的格局，阴不断在增长，而阳不断在萎缩，直到坤卦，变成六爻皆阴，变成重阴。而重阴必阳，所以，到了下一卦，到了复卦，又重新转入阳的格局。于是我们又看到了一个阳爻不断增长，阳气的释放渐渐增强的过程。这里为什么要起复卦这个名呢？复就有重复、来复的意思，到了这个点上，又开始新一轮“阳生阴长，阳杀阴藏”的变化，所以这一卦取名为复。在上述这个变化过程中，我们还应留意另一个问题，这就是重阴必阳的变化，一阳生的变化并不发生于立春，而是发生在隆冬。同样，重阳必阴的变化，姤所涵的一阴生的变化，也没有发生在立秋，而是在盛夏。这又反映了阴阳的另一个显著的特征，那就是阳生于阴，阴生于阳；阴中有阳，阳中有阴。从上面这个过程我们可以看到，讨论阴阳，讨论中医，如果结合《周易》来谈，会显得更方便、更直观，更有助于我们了解她的确切内涵。所以，历代都有人强调医易的关系，尤其孙思邈指出：“不知易不足以为大医。”这一点我们应该引起重视。
（2）主导问题
What is the most important thing in Traditional Chinese Medicine (TCM)? What is the core essence of TCM? Everything revolves around it; without it, nothing can function. What is this thing? It is Yin and Yang (Yin-Yang)! The opening chapter of *Suwen: Treatise on the Correspondence of Yin and Yang to Phenomena* (*Suwen: Yin-Ying Xiang Da Lun*) states: "Yin and Yang are the Way of Heaven and Earth, the general principles of all things, the parents of change, the origin of life and death, and the repository of spiritual clarity. In treating diseases, one must seek the root." This passage from *Suwen* offers a highly condensed and summarized exposition of Yin and Yang. Any scholarship we pursue, especially TCM, cannot be separated from Heaven and Earth, and Yin and Yang constitute the Way of Heaven and Earth; they are the general principles of all things. Considering "all things" and "general principles," one can weigh their significance—is there anything that can escape the scope of Yin and Yang? They are the parents of change. When we explore phenomena, we are essentially exploring their changes—changes in time and space. What causes these changes? It is Yin and Yang. Whether we engage with society or nature, whether dealing with animals or plants, organic or inorganic matter, the universe or the galaxy, the entire process is nothing but a cycle of generation and destruction. How does this generation and destruction arise? Its ultimate origin lies in Yin and Yang. Furthermore, regarding the "repository of spiritual clarity," "spiritual clarity" refers to spirit and thought, so this aspect has a particularly significant relationship with human beings themselves. How does spirit arise? It is still related to Yin and Yang. Finally, we must discuss the principle of seeking the root in treatment. Nowadays, people know to say: Western medicine treats symptoms, while TCM treats the root. But when asked how TCM treats the root, or through what means it achieves this, one often cannot answer. Actually, this root is still Yin and Yang; one must seek it within Yin and Yang. Yin and Yang are thus the most fundamental elements relating to every aspect. What understanding do you have of Yin and Yang? Have you reached the height presented in the *Neijing* (Inner Canon)? When I teach undergraduate and graduate students, I like to pose this question. Their answers usually consist of the points found in the *Basic Theory of TCM* textbook: opposition and restriction, mutual rooting and usage, waxing and waning balance, and mutual transformation, etc. However, if questioned further, they cannot answer. Merely knowing these concepts is not enough for studying Yin and Yang. You must have a genuine perception of how they oppose each other and how they mutually root and use each other. For any change in things, you should be able to attribute it to Yin and Yang; even in every gesture and movement, you should be able to distinguish and perceive Yin and Yang. Only in this way can Yin and Yang be utilized by you, and only then can you use Yin and Yang to solve real practical problems.
(1) The Relationship between Yin and Yang
Yin and Yang discuss the matters between the two entities of Yin and Yang. Since there are two, there is an issue of mutual relationship, which is also the most critical question in the study of Yin and Yang. This aforementioned relationship is profoundly discussed in *Suwen: Treatise on the Correspondence of Yin and Yang to Phenomena*, specifically in the phrase "Yang generates, Yin grows; Yang kills, Yin stores." This sentence basically encompasses the main aspects of Yin and Yang; therefore, once this is understood, the study of Yin and Yang can be considered fundamentally resolved. "Yang generates, Yin grows; Yang kills, Yin stores" mainly discusses the changes of Yin and Yang throughout the year and the growth conditions of all things. "Yang generates, Yin grows" primarily refers to the first half of the year, i.e., the changes of Spring and Summer. In this process, Yang gradually generates, and Yin gradually grows, and the relationship between the two is very harmonious. Relating this to specific nature, after spring days become longer and temperatures rise, we can feel the continuous increase of Yang Qi (Vital Energy) everywhere. What about Yin? "Yang transforms into Qi, Yin forms into shape." These shaped things, belonging to Yin, flourish continuously along with the increase of Yang, presenting a truly thriving scene. This process is truly Yang generating and Yin growing, like a husband singing and wife following. It seems different from the previously mentioned relationships of opposition and waxing/waning; it is not that when Yang arises, all things perish. It is completely not such a situation. If we were to describe this process using modern language, Yang Qi would be akin to energy. We can imagine such an energy reservoir between Heaven and Earth. During the two seasons of Spring and Summer, energy is in a state of release. With the release of energy, all things receive this supply and gradually grow and flourish. Otherwise, on what basis would all things grow and flourish? It is precisely because of the release of Yang Qi and energy that this occurs. This is "Yang generates, Yin grows." So, what is "Yang kills, Yin stores"? This refers to the changes of Autumn and Winter. Do not view "Yang kills" as actual destruction; "Yang kills" is a relative concept to "Yang generates." Since the "Yang generates" of Spring and Summer refers to the release of Yang and energy, will this release proceed endlessly? It should not. This is like boxing: if the fist extends and strikes but remains in that state, one cannot deliver a second blow. Therefore, one must retract the fist first to strike again. Yang Qi is the same; can it always generate and release? No! Such a state cannot be sustained. Thus, after generation and release reach a certain degree, it gradually transitions into storage. This storage of Yang Qi, relative to release, is called "Yang kills." When Yang kills, energy is stored away. Heaven, Earth, and all things no longer receive this energy supply, so the growth of all things tends to stop, and they gradually wither and decay. This is the autumn and winter scenery we see. The line "Autumn wind blows across the Wei River, fallen leaves fill Chang'an" describes this state of肃杀 (severe/cold killing) and storage. The aforementioned process is cyclical and endless. Therefore, after storage reaches a certain degree, a new round of generation and release begins. This is what *Suwen* calls "Extreme Yang transforms into Yin, Extreme Yin transforms into Yang." Yang refers to the process of generation and release, while Yin refers to the process of storage. Referring to Spring and Summer as Yang and Autumn and Winter as Yin also points to this process. Using *Suwen*'s "Extreme Yang transforms into Yin, Extreme Yin transforms into Yang" to explain this transition is very vivid. To better understand this process, we can combine some knowledge from the *Zhouyi* (Book of Changes). The *Zhouyi* is a book specifically discussing the changes of Yin and Yang, representing these changes with a two-dimensional image, making the changes more intuitive and clear. Especially for describing the Yin and Yang changes of a year, it has special "Twelve Message Hexagrams": Fu (Return), Lin (Approach), Tai (Peace), Da Zhuang (Great Strength), Gou (Meeting), Qian (The Creative), Gou (Coming to Meet), Dun (Retreat), Pi (Standstill), Guan (Contemplation), Bo (Splitting Apart), Kun (The Receptive). If memorized by a poem, it is "Fu, Lin, Tai, Zhuang, [Gou], Qian, Gou, Dun, Pi, Guan, Bo, Kun, Two Sixes." Among them, the hexagram Fu corresponds to the changes of the eleventh lunar month, and so on: Lin for the twelfth month, Tai for the first month, Da Zhuang for the second month, [Gou] for the third month, Qian for the fourth month, Gou for the fifth month, Dun for the sixth month, Pi for the seventh month, Guan for the eighth month, Bo for the ninth month, and Kun for the tenth month. The aforementioned Twelve Message Hexagrams are also called "Derived Hexagrams" in the Yi system. They are formed by overlapping two Trigrams. Trigrams refer to the commonly known Eight Trigrams system, while Derived Hexagrams refer to the commonly known Sixty-Four Hexagrams system. From the Twelve Message Hexagrams, we can see that except for the Qian and Kun hexagrams, the other ten hexagrams are mixed with Yin and Yang lines, containing both Yin and Yang. However, Qian and Kun are different; they are pure Yin and pure Yang. The Qian hexagram is formed by overlapping two pure Yang Trigrams (Qian), so it is also called the Double Yang Hexagram. The Kun hexagram is formed by overlapping two pure Yin Trigrams (Kun), so it is also called the Double Yin Hexagram. Starting from the Fu hexagram, we can see that Yang lines gradually increase, marking the continuous enhancement of the generation and release of Yang Qi, until reaching the Qian hexagram, where all six lines are Yang, becoming Double Yang, and the generation and release of Yang reach their maximum extent. What happens next? Extreme Yang transforms into Yin. Therefore, at the next hexagram, Gou, the aforementioned Yang pattern undergoes a fundamental change; Yang no longer increases, but Yin quietly arises. The month corresponding to the Gou hexagram is the fifth month, and the transformation of "Extreme Yang transforms into Yin" corresponding to the Gou hexagram occurs at the Summer Solstice in May. "Solstice" does not mean arrival; it means limit. Summer is Yang. At the point of the Summer Solstice, the growth of Yang has reached its limit. Since things reverse when they reach extremes, there is this change of "Summer Solstice—Yin Generates," leading to the change of "Extreme Yang generates Yin, Extreme Yang transforms into Yin." After the Gou hexagram, we see another completely different pattern: Yin continues to grow, while Yang continuously shrinks, until reaching the Kun hexagram, where all six lines are Yin, becoming Double Yin. And Extreme Yin transforms into Yang. Therefore, at the next hexagram, Fu, it re-enters the Yang pattern. Thus, we see again a process where Yang lines continuously increase and the release of Yang Qi gradually strengthens. Why is this hexagram named Fu? "Fu" means repetition or return. At this point, a new round of "Yang generates, Yin grows; Yang kills, Yin stores" begins, so this hexagram is named Fu. In the above change process, we should also pay attention to another issue: the change of "Extreme Yin transforms into Yang" and the generation of "One Yang" does not occur at the Beginning of Spring, but in the depths of winter. Similarly, the change of "Extreme Yang transforms into Yin" and the generation of "One Yin" contained in Gou does not occur at the Beginning of Autumn, but in midsummer. This reflects another significant characteristic of Yin and Yang, namely that Yang is born from Yin, and Yin is born from Yang; Yin contains Yang, and Yang contains Yin. From the above process, we can see that discussing Yin and Yang, or discussing TCM, if combined with the *Zhouyi*, appears more convenient, more intuitive, and helps us understand its exact connotation better. Therefore, people in past dynasties have emphasized the relationship between Medicine and the Yi (Changes). Especially Sun Simiao pointed out: "He who does not know the Yi is not qualified to be a great physician." We should attach importance to this point.
(2) The Dominant Issue