通过上述讨论，我们看到了这样一种阴随阳生而长，阴随阳杀而藏的关系，这就要求我们明确两个更具体的主导问题。第一个主导，是阴阳之间协同为主导，而非对立制约为主导。这也是前面所讲的“夫唱妇随”的关系。阴阳在现实生活中一个更为具体的例子就是男女，就是夫妇，就是一个家庭关系。大家设想一下，如果一个家庭中，夫妇两个以对立为主，一个面南，一个面北，水火不相容，那这个日子怎么过，连基本的日子都没法过，更不要谈事业了。所以，家庭的关系，夫妇的关系，阴阳的关系应该以协同为主导。第二个主导是阴阳之间阳为主导，这个主导实际上已经包含在第一个主导里。这个主导说明在阴阳之间，阳的变化起主导的作用、决定的作用。作为阴它是随着阳的变化而变化。有关这层主导关系，我们可以在自然、社会的方方面面感受到。前面《素问》所说的“阳生阴长，阳杀阴藏”，实际上就是我们常说的生、长、收、藏。生、长、收、藏虽然用于表述一年里万物的变化情况，即春生、夏长、秋收、冬藏，但更实质的东西，更内涵的东西，则是阳的变化。是阳的春生、夏长、秋收、冬藏才导致了这个万物的生、长、收、藏。有关这一点，董仲舒在他的《春秋繁露》里说得很清楚：“物随阳而出入，数随阳而终始。……阳者岁之主也，天下之昆虫，随阳而出入。天下之草木随阳而生落。天下之三王随阳而改正。”大家考察一下自然，看是不是这么回事呢？确实就是这么回事。草木也好，昆虫也好，植物也好，动物也好，它确实是在随着春、夏、秋、冬的变化而变化。而春夏秋冬怎么来？春夏秋冬由什么来决定？大家知道是由太阳的视运动决定的。太阳沿黄道运行一周，就形成了一年的春夏秋冬。因此，春夏秋冬即反映了时间的变化，而更重要的是反映了阳的状态。什么叫春呢？春实际上就是阳气处于生的状态所占的时段，依次，夏就是阳气处于长的状态所占的时段；秋就是阳气处于收的状态所占的时段；冬为阳气处于藏的状态所占的时段。由阳的变化产生了春夏秋冬，而万物又依着这个春夏秋冬的变化而变化，它们之间就是这么一种关系。从社会的角度，阳（男）作为主导的地位就更为明确，这一点大家有目共睹，不需多谈。上面我们谈阴阳用了十二消息卦，看到这些卦象的变化，也许大家还是容易将阴阳分开来，对立来看。比如从复到乾这个阳局的变化，明明是阳日增，阴日消，我多你少，你死我活，这个对立好像很鲜明。其实，我们不能这样看。阳日增，说的是这个阳的生发，释放的增加，阴日少，不是说随着阳的增加，有另外一个独立的东西（阴），它在慢慢的减少。如果我们这样来理解阴阳，那就会出根本上的问题。阴日少，我们确实看到这个阴爻从复卦以后，在慢慢减少，直到乾卦减为零，那，我们是否可以说在乾所主的这个时候，是纯阳无阴呢？一点阴都没有，那不成了孤阳！《内经》说：孤阳不生，孤阴不长。可是我们看到夏三月的景象是万物蕃秀，真正的一派繁荣。可见我们不能这样来理解阴阳。上述这个阴日少，说的是随着阳气生发、释放的增加，阳的收藏自然就日益地缩减，前面我们不是申明过，阳的收藏状态为阴吗？释放增加了，收藏自然地就减少，不可能又释放，又收藏，就像我们的拳头，打出去再收回来，收回来才能再打出去，不可能在同一个时候，又收回来，又打出去。这就是阴阳的消长关系。所以，虽然是在谈消长，其实说的还是一个问题，即阳气的变化问题。十二消息卦的另一个层面，也就是阴局这个层面，也非常容易发生误解。大家看从姤卦以后，阴爻日增，阳爻日减，很多人就认为这是阴日盛，阳日衰，是一个阴盛阳衰的过程。我们从卦上看，从表面看，好像是这么回事。但，究竟的思维一下，就知道这个看法有问题。为什么说这个看法有问题呢？大家可以思考，从姤以后，也就是从夏至以后，一阴始生，阳气逐渐由释放转入收、转入藏。那么，这个收藏的目的是什么呢？就像我们的拳头打出去，要收回来，收回来的目的是为了重新打出去。同样，阳气要收藏，收藏的目的是为了能够重新释放。如果收藏以后，阳气反而衰减了，那它怎么能够再释放？实际上释放就会有消耗，就会有衰减，而收藏的目的正是为了补偿这个消耗、这个衰减。因此，从量上来说，这个秋冬的过程，这个阳气收藏的过程，也就是我们前面认为的这个“阴盛阳衰”的过程，阳气的量不但没有衰减，反而得到了补偿，得到了增加。只有这样，才有可能经过收藏以后再发动新一轮的生发、释放。联系我们人体，白天工作的过程，其实就是阳气释放的过程，而晚上的休息，则是阳气的收藏过程。休息的目的是什么呢？是为了白天更好的工作，是为了获得更旺盛的精力，如果通过休息，阳气反而衰减了，那么这个精力怎么旺盛？那还有谁愿意睡觉、愿意休息？所以，我们只要一思考，上面这个问题就不难解决。阴阳的问题是一而二，二而一。分开来好像有两个，一个男、一个女，好像是两个确凿的、独立的东西。但，合起来的实质却是一。所以，阴阳的问题如果我们只能分开来看，而不能合二为一，那就很难看到点子上。就比如寒热这个问题，寒热如同水火，很难把它们扯到一块。这应该是两个截然不同的东西，无论如何都不能把它合二为一。可实际上并不是这么回事，我们看到的这个截然不同，只是显现上的不同，如果进一步从深层去考虑，发现它还是一个阳气的问题。前面我们说过，阳气好比能量，好比热能。春夏的天气为什么温热？就是因为这个阳气的释放造成的，属热的东西释放出来了，那天气当然就变热了。到了秋冬，秋天的天气为什么凉？冬天的天气为什么寒冷？热的东西不释放了，收藏起来了，天气当然就变得寒冷。也就是说，寒热是伴随阳的生长收藏的一个表象，阳气释放了，天气就变热，阳气收藏了，天就变冷，并不是在热之外又有一个独立的属寒的东西。上述这个问题，一个谈实质，一个讲显现，对这个过程我们应该多思维之，善思维之。要是这个过程我们思考得清清楚楚，明明白白，那阴阳的问题可以说基本地解决了。《素问》强调：“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。然其要一也。”“知其要者，一言而终，不知其要，流散无穷。”这个“数之可十，推之可百，数之可千，推之可万”其实就是讲显现，是从现象上讲。而这个不可胜数的显现，就其实质而言却只是一个。知道了这个实质，就可以一言而终，就可以“能知一，万事毕”，而不知道这个实质，则必会流散无穷。上述这个阴阳变化，上述这个主导关系，我们还可以从最原始的天文测算过程去体悟。大家知道《周髀算经》这本书吧，这部书记述了最原始的测量太阳运行轨迹，也就是一年二十四节气的方法。就是在日中正午的时候，在太阳下立一个八尺的圭表，圭表的投影叫晷影，测量这个晷影的长度，就能够知道太阳运行到了什么地方，就能够确定出二十四节气。《周髀算经》告诉我们，晷影最长的长度是一丈三尺五寸，最短的长度是一尺六寸。大家可以思考，最长的这个晷影应该对应哪一天？最短的这个晷影应该对应哪一天？最长晷影的这一天应该是冬至这一天，相反的，最短晷影的这一天就是夏至这一天。晷影也就是太阳的阴影，盛夏的时节我们外出，大家总是喜欢走在树阴下面，或者总是希望来一片青云，为什么呢？因为树阴把太阳遮住了，青云把太阳光收藏起来了。所以，我们马上就会感受到清凉。因此，我们可以把上述的这个晷影当作是阳的收藏状态的一个尺度。为什么冬至的晷影最长呢？因为这个时候阳的收藏最厉害。冬至一过，我们看到这个晷影就日渐缩短，这反映了阳的收藏在减弱，随着这个收藏的减弱，阳气自然日益显露，日益生发、释放。所以，冬至以后，白天也一日一日增长，黑夜一日日缩短，这些都是收藏与显露，收藏与释放的变换。上述这个日益短缩的晷影到了夏至这一天，缩至了一尺六寸，一尺六寸与一丈三尺五寸相比，零头都不到。这个时候的阳气充分显露出来了，几乎没有什么遮拦，这就使得阳气的释放达到了最大的程度。然而重阳必阴，所以，夏至一过，这个晷影就一天天地变长。与之相应，白天也一天天地缩短，黑夜一天天地延长。阳气在充分地释放以后，又渐渐转入到收藏。由上面这个晷影的伸缩，我们可以看到，一年四季的变化，二十四节气的变化，其实就是阳气收藏与释放之间的变化。我们抓住了这个主导，阴阳的方方面面就会自然地连带出来。
（3）体用关系
Through the above discussion, we have observed a relationship where Yin grows as Yang generates, and Yin stores as Yang kills (肃杀/declining). This requires us to clarify two more specific guiding principles. The first guiding principle is that the relationship between Yin and Yang is primarily synergistic, rather than one of opposition and restriction. This is also the relationship described earlier as "the husband sings, the wife follows." A more concrete example of Yin and Yang in real life is men and women, husbands and wives, and family relationships. Imagine if, in a family, the couple were primarily opposed to each other, one facing south and the other north, with water and fire incompatible; how could they live? They couldn't even maintain basic daily life, let alone pursue careers. Therefore, the relationship of the family, the couple, and Yin and Yang should be guided by synergy. The second guiding principle is that among Yin and Yang, Yang takes the leading role. This leadership is actually already contained within the first principle. This principle indicates that in the relationship between Yin and Yang, changes in Yang play a leading and decisive role. Yin changes in accordance with Yang. We can perceive this hierarchical relationship in all aspects of nature and society. What was said in the *Suwen* (Basic Questions) earlier, "Yang generates, Yin grows; Yang kills, Yin stores," is actually what we commonly refer to as generation, growth, harvesting, and storage. Although generation, growth, harvesting, and storage are used to describe the changes of all things throughout the year—spring generation, summer growth, autumn harvesting, winter storage—the more substantial and intrinsic aspect is the change of Yang. It is Yang's spring generation, summer growth, autumn harvesting, and winter storage that lead to the generation, growth, harvesting, and storage of all things. Regarding this point, Dong Zhongshu stated clearly in his *Chunqiu Fanlu* (Luxuriant Dew of the Spring and Autumn Annals): "Things enter and exit following Yang; numbers begin and end following Yang... Yang is the master of the year; insects of the world enter and exit following Yang; plants and trees of the world grow and fall following Yang; the three kings of the world correct their calendars following Yang." If you examine nature, does it not work this way? Indeed, it does. Whether plants, insects, flora, or fauna, they indeed change in response to the variations of spring, summer, autumn, and winter. But how do spring, summer, autumn, and winter come about? What determines them? As everyone knows, they are determined by the apparent motion of the sun. One complete orbit of the sun along the ecliptic forms the four seasons of a year. Therefore, spring, summer, autumn, and winter reflect not only the passage of time but, more importantly, the state of Yang. What is spring? Spring is actually the period during which Yang Qi (Vital Energy) is in a state of generation; similarly, summer is the period when Yang Qi is in a state of growth; autumn is the period when Yang Qi is in a state of harvesting; and winter is the period when Yang Qi is in a state of storage. Changes in Yang produce spring, summer, autumn, and winter, and all things change according to these seasonal variations; this is the relationship between them. From a social perspective, the dominant status of Yang (male) is even more evident, a fact visible to all, requiring no further elaboration.
When discussing Yin and Yang using the Twelve Phase-Generating Hexagrams (Twelve Xi Xiao Gua), observing the changes in these hexagram images, perhaps many people still tend to view Yin and Yang separately and oppositely. For example, in the change from the Fu (Return) hexagram to the Qian (Creative) hexagram, it is clearly Yang increasing day by day and Yin decreasing day by day, "I gain, you lose; you die, I live," making this opposition seem very distinct. In fact, we cannot view it this way. "Yang increases day by day" refers to the increase in the generation and release of Yang; "Yin decreases day by day" does not mean that as Yang increases, another independent entity (Yin) is slowly diminishing. If we understand Yin and Yang in this manner, fundamental errors will arise. Regarding the decrease in Yin, we indeed see the Yin line gradually decreasing after the Fu hexagram until it reaches zero in the Qian hexagram. So, can we say that during the time governed by Qian, there is pure Yang without Yin? If there is absolutely no Yin, wouldn't that become "Lone Yang"? The *Neijing* (Inner Canon) states: "Lone Yang cannot generate; Lone Yin cannot grow." Yet, we observe the scene in the third month of summer, where all things flourish and thrive, presenting a true picture of prosperity. Thus, we cannot understand Yin and Yang this way. The aforementioned "Yin decreases day by day" means that as the generation and release of Yang Qi increase, the storing function of Yang naturally diminishes day by day. Didn't we previously state that the storing state of Yang is Yin? As release increases, storing naturally decreases; it is impossible to both release and store simultaneously. It is like our fist: we punch out, then pull back; we must pull back before we can punch out again. It is impossible to pull back and punch out at the same time. This is the waxing and waning relationship of Yin and Yang. Therefore, although we are discussing waxing and waning, we are essentially discussing one issue: the changes of Yang Qi.
Another level of the Twelve Phase-Generating Hexagrams, namely the Yin phase, is also very prone to misunderstanding. Looking at the situation after the Gou (Meeting) hexagram, the Yin lines increase day by day while the Yang lines decrease. Many people believe this represents Yin flourishing and Yang declining, a process of Yin excess and Yang deficiency. Visually, from the hexagrams, it seems so. However, upon deeper reflection, one realizes this view is problematic. Why is this view problematic? Consider this: after Gou, which corresponds to the Summer Solstice, the first Yin begins to generate, and Yang Qi gradually transitions from release to storage. Then, what is the purpose of this storage? Just as punching out requires pulling back, and pulling back is for the purpose of punching out again, similarly, Yang Qi needs to store itself, and the purpose of storage is to enable subsequent release. If Yang Qi were to decline after storage, how could it release again? Actually, release involves consumption and decline, and the purpose of storage is precisely to compensate for this consumption and decline. Therefore, quantitatively speaking, the process of autumn and winter, which is the process of Yang Qi storage—and which we previously considered as "Yin excess and Yang deficiency"—does not see a decline in the quantity of Yang Qi; rather, it is compensated and increased. Only in this way is it possible to initiate a new round of generation and release after storage.
Connecting this to the human body, the process of working during the day is essentially the release of Yang Qi, while resting at night is the storage of Yang Qi. What is the purpose of rest? It is to work better during the day and to gain more vigorous energy. If rest caused Yang Qi to decline, how could energy be vigorous? Who would be willing to sleep or rest? Thus, once we think about it, the above problem is not difficult to resolve. The issue of Yin and Yang is "one becoming two, and two becoming one." Separately, it seems there are two, a man and a woman, appearing as two distinct, independent entities. But combined, their essence is one. Therefore, if we can only view Yin and Yang separately and fail to integrate them into one, it will be difficult to grasp the essence.
Take the issue of Cold and Heat, for example. Cold and Heat are like water and fire, hard to associate. They should be two completely different things, impossible to merge into one. However, this is not the case. The stark difference we see is merely superficial. If we consider it deeply, we find it is still an issue of Yang Qi. As mentioned earlier, Yang Qi is akin to energy, akin to thermal energy. Why is the weather warm in spring and summer? Because of the release of Yang Qi; when heat-related substances are released, the weather naturally becomes hot. In autumn and winter, why is autumn cool and winter cold? Because heat is no longer released but stored, so the weather naturally becomes cold. That is to say, Cold and Heat are manifestations accompanying the generation, growth, harvesting, and storage of Yang. When Yang releases, the weather becomes hot; when Yang stores, the weather becomes cold. There is no independent entity of "Cold" existing outside of "Heat." Regarding the above issues, one discusses essence, and the other discusses manifestation. We should ponder and reflect well on this process. If we think through this process clearly and distinctly, the issue of Yin and Yang can be said to be basically resolved. The *Suwen* emphasizes: "Yin and Yang, counted, can reach ten; extended, a hundred; counted, a thousand; extended, ten thousand; vastness beyond counting. Yet their essence is one." "He who knows the essence concludes in one word; he who does not know the essence scatters infinitely." The phrase "counted, ten; extended, hundred; counted, thousand; extended, ten thousand" actually refers to manifestation, speaking from the perspective of phenomena. This infinite number of manifestations, in terms of essence, is just one. Knowing this essence allows one to conclude in one word, achieving "Knowing One, all affairs are completed"; not knowing this essence leads to infinite scattering.
Regarding the changes of Yin and Yang and the aforementioned guiding principles, we can also comprehend them through the most primitive astronomical calculation processes. Everyone knows the book *Zhoubi Suanjing* (The Arithmetical Classic of the Gnomon and the Circular Paths of Heaven), which records the most primitive method of measuring the sun's trajectory, i.e., the twenty-four solar terms. At noon, when the sun is directly overhead, a gnomon (Guibiao) eight chi tall is erected under the sun. The shadow cast by the gnomon is called the gnomic shadow (Guiying). Measuring the length of this shadow allows us to know where the sun has moved and to determine the twenty-four solar terms. The *Zhoubi Suanjing* tells us that the longest gnomic shadow is one zhang and three chi five cun, and the shortest is one chi six cun. You may ponder: which day does the longest shadow correspond to? Which day does the shortest shadow correspond to? The day with the longest shadow should be the Winter Solstice; conversely, the day with the shortest shadow is the Summer Solstice. The gnomic shadow is the sun's shadow. In midsummer, when we go out, we always prefer to walk under tree shade or hope for clouds, right? Why? Because tree shade blocks the sun, and clouds store the sunlight. Thus, we immediately feel cool. Therefore, we can regard the aforementioned gnomic shadow as a measure of the storing state of Yang. Why is the gnomic shadow longest at the Winter Solstice? Because at this time, the storing of Yang is most intense. After the Winter Solstice, we see the shadow gradually shorten, reflecting that Yang's storing is weakening. As storing weakens, Yang Qi naturally becomes more manifest, generating and releasing day by day. Therefore, after the Winter Solstice, days grow longer and nights shorter day by day; these are transformations between storing and manifesting, storing and releasing.
This increasingly shortening gnomic shadow reaches its minimum of one chi six cun at the Summer Solstice. Compared to one zhang three chi five cun, one chi six cun is less than a fraction. At this time, Yang Qi is fully manifested, with almost no obstruction, allowing the release of Yang Qi to reach its maximum extent. However, extreme Yang transforms into Yin. Therefore, after the Summer Solstice, the shadow lengthens day by day. Correspondingly, days shorten and nights lengthen day by day. After fully releasing, Yang Qi gradually transitions back to storage. From the extension and contraction of the gnomic shadow, we can see that the changes of the four seasons and the twenty-four solar terms are essentially changes between the storing and releasing of Yang Qi. By grasping this guiding principle, all aspects of Yin and Yang will naturally follow.
(3) Ti-Yong Relationship