《易》曰∶太极生两仪，两仪生四象，四象生八卦，八卦相错，万物生焉。太极，阴含
阳也；仪象，阳分阴也。阳不能自立，必得阴而后立，故阳以阴为基，而阴为阳之母；阴不
能自见，必待阳而后见，故阴以阳为统，而阳为阴之父。根阴根阳，天人一理也。以定位言
，则阳在上，阴在下，而对待之体立；以气化言，则阴上升，阳下降，而流行之用宏。
请以卦论∶干为天，干之左为坎水，右为兑水，是水行天上也，而非水也，乃水之阴气
上升于天也；若阴升于天，而气化之不及，则阴霾四起，而天象变矣。坤为地，坤之左为震
之雷火、巽之风火、离之正火，是火出地下也，而非火也，乃火之阳气下降于地也；若阳降
于地，而气运之不周，则赤卤不毛，而地象变矣。然论卦象犹虚也，请实征诸时。试观一岁
之间，夏至以后，酷暑炎蒸，若非阴气潜生，大雨时行，则大地皆成灰烬矣。阴气上升，其
明证也。且阴气上升于天，得天之布 ，而阴气乃弥纶于无际。冬至以后，阴凝寒冱，
若非阳气潜藏，水泉流动，则世人皆成僵冻矣。阳气下降，其明证也。且阳气下降于地，得
地之酝酿，而阳气乃发育于无穷。独是阴气上升，而非自升，必得阳气乃升。地之阳，即天
下降之阳，以阳助阴升，故不曰阳升，而曰阴升。阳气下降，而非虚降，必含阴气以降。天
之阴，即地上升之阴，以阴随阳化，故不曰阴降，而曰阳降。若是阴阳互根，本是一气，特
因升降而为二耳！
以人言之。人之阴升，脾胃水谷精微之气，上升于肺，如经所谓饮入于胃，游溢精气，
上输于脾，脾气散精，上输于肺，是即水行天上也。气中有水，故曰阴升，然水不离乎气也
。若非气水蒸腾，而为邪水上泛，则水溢高源，而肺胀、喘嗽诸证生矣。然气水既生于胃，
必胃中水谷充满，而后阴气乃旺，经故曰∶精气生于谷气。若胃气自病，则生化之源绝，安
望
得肾之含纳，而阳气乃收藏不越。人之阳降，肺之阳气下降于肾，如天之阳气潜藏于地，是
即火出地下也。水由气化，故曰阳降，然气不离乎水也。若非气水涵濡，而为燥阳下降，则
金枯水竭，而劳咳、骨蒸诸证生矣。然则阳气不可虚降，必含阴气以降。肺之真阴，即脾、
胃、肾上升之阴。惟脾、胃、肾之阴上升于肺，得肺之敷布，而阴气乃充周一身。经故曰∶肾
上连肺。又曰∶无阳则阴无以生，无阴则阳无以化。
然而阴阳升降，不可得而见也，请借证釜甑。釜中之水谷，水也；釜底之火，火也。釜
上之气，即为阳气；气中之水，即为阴气。然必釜中水谷充满，又得釜底之火以熏蒸之，釜
上之盖以统束之，而后气中之水， 煦育，上蒸下布。气中有水，即是阴升；水由
气化，即为阳降。若釜中水谷不充，则无米之炊，将见釜底之火，仅存虚阳，釜上之盖，亦
为虚器。又或釜中虽有水谷，而釜底无火，不独精气不能蒸运，即渣滓亦难销熔；釜上无盖
，不独统摄无权，亦且漫溢不治。然则阴阳二气，非相需而不可须臾离者哉？
然就二气而权衡之，阴承阳，阳统阴，阳气一分不到即病，阳气一分不尽不死，人自当
以阳气为重。然阳气固重，阴气亦重，何也？人事与病，多致阴伤者也，经云∶静则神藏，
动则消亡。日用操劳，皆动机也，动则所生之少，不敌所耗之多；病亦动机也，动则六气皆
从火化，化火则必伤阴，则又当以阴气为重。譬如行舟，行者气也，行之者水也，水足气始
旺也。再譬诸灯∶灯火，火也；油，水也，油足火始明也。气为血帅，血又为气航。此阳统
阴而基于阴之理也。若无阴，则阳气亦无根据而亡矣。（阴液脱者死，大肉脱者亦死。）故阴阳
二字，不读曰阳阴，而读曰阴阳，其亦可以恍然悟矣！
《易经》说：太极产生两仪，两仪产生四象，四象产生八卦，八卦交错变化，万物由此生成。太极之中，阴包含阳；两仪之象，阳分出了阴。阳不能独立存在，必须得到阴的支持才能确立，所以阳以阴为基础，阴是阳的母亲；阴不能独自显现，必须依赖阳才能呈现，所以阴以阳为统领，阳是阴的父亲。根源于阴也根源于阳，天与人的道理是一致的。从固定的位置来说，阳在上，阴在下，相对立的形体就确立了；从气化运动来说，阴气上升，阳气下降，流行变化的功用就宏大起来。
让我们用卦象来论述：乾象征天，乾的左边是坎水，右边是兑水，这是水行于天上，但并非真正的水，而是水的阴气上升到了天空；如果阴气上升到天空，而气化作用达不到，那么阴霾就会四处兴起，天象就会发生变化。坤象征地，坤的左边是震雷、巽风、离火，这是火出于地下，但并非真正的火，而是火的阳气下降到了地面；如果阳气下降到地面，而气运周流不全面，那么土地就会变成赤色盐碱地而不长草木，地象就会发生变化。然而谈论卦象还比较抽象，请让我们实际考察四季时令。试看一年之中，夏至以后，酷暑炎热蒸腾，如果不是阴气在暗中滋生，大雨适时降下，那么大地都会变成灰烬。这就是阴气上升的明证。而且阴气上升到天空，得到天的布散覆盖，阴气才弥漫于无边无际之中。冬至以后，阴寒凝结冻结，如果不是阳气在暗中潜藏，泉水依然流动，那么世人都会变成僵冻尸体。这就是阳气下降的明证。而且阳气下降到地面，得到地的酝酿培育，阳气才能在无穷中发育生长。只是这阴气上升，并不是自己上升，必须得到阳气的帮助才能上升。地上的阳气，就是从天下降的阳气，以阳助阴上升，所以不说阳升，而说阴升。阳气下降，并不是虚空下降，必须含有阴气才能下降。天上的阴气，就是从地上升的阴气，以阴随阳变化，所以不说阴降，而说阳降。像这样，阴阳互根，本是一气，只是因为升降运动而分为二罢了！
从人体来说。人体的阴气上升，是指脾胃运化水谷产生的精微之气，上升到肺，正如经典所说“饮入于胃，游溢精气，上输于脾，脾气散精，上输于肺”，这就是水行于天上。气中含有水，所以叫阴升，但水离不开气。如果不是气与水共同蒸腾，而是邪水上泛，那么水就会溢出高源，导致肺胀、喘咳等症状产生。既然气水生于胃，必须胃中水谷充满，然后阴气才会旺盛，经典所以说：“精气生于谷气。”如果胃气自身生病，那么生化之源断绝，哪里还能指望肾的含纳功能，使阳气收藏不外泄呢？人体的阳气下降，是指肺的阳气下降到肾，就像天的阳气潜藏于地，这就是火出于地下。水由气化生，所以叫阳降，但气离不开水。如果不是气与水相互涵濡，而是燥热的阳气下降，那么肺金枯槁、肾水枯竭，导致劳嗽、骨蒸等症状产生。那么阳气不可虚空下降，必须含有阴气才能下降。肺的真阴，就是脾、胃、肾上升的阴气。只有脾、胃、肾的阴气上升到肺，得到肺的敷布，阴气才能充周一身。经典所以说：“肾上连肺。”又说：“无阳则阴无以生，无阴则阳无以化。”
然而阴阳的升降，是不可见的，请借用锅和蒸笼来证明。锅中的水谷，是水；锅底下的火，是火。锅上的蒸汽，就是阳气；蒸汽中的水分，就是阴气。但是必须锅中水谷充满，又得到锅底之火熏蒸它，加上锅盖统束它，然后蒸汽中的水分，才能温煦养育，向上蒸腾向下布散。气中有水，就是阴升；水由气化，就是阳降。如果锅中水谷不充足，那就是无米之炊，只见锅底之火仅存虚阳，锅盖也成了空器。或者虽然锅中有水谷，但锅底没有火，不仅精气不能蒸运，就连渣滓也难以销熔；如果没有锅盖，不仅统摄无权，而且漫溢无法治理。那么阴阳二气，不是相互需要、片刻也不能分离的吗？
然而就这两气权衡来看，阴承受阳，阳统领阴，阳气有一分不到就会生病，阳气有一分耗尽就会死亡，人自然应当重视阳气。但是阳气固然重要，阴气也重要，为什么呢？人事活动和疾病，大多损伤阴气，经典说：“静则神藏，动则消亡。”日常操劳，都是动，动则所生的少，抵不过所消耗的多；疾病也是动，动则六气都从火化，化火必然伤阴，这时又应当重视阴气。譬如行船，行驶的是气，承载的是水，水足气才旺。再譬如灯：灯火是火，油是水，油足火才明亮。气是血的统帅，血又是气的航船。这就是阳统领阴而基于阴的道理。如果没有阴，阳气也就没有根据而消亡了。（阴液脱失者死，大肌肉消瘦脱失者也死。）所以“阴阳”二字，不读作“阳阴”，而读作“阴阳”，这也让人恍然大悟了！
The *I Ching* (Book of Changes) states: "Taiji generates Liangyi (Two Modes), Liangyi generates Sixiang (Four Images), Sixiang generates Bagua (Eight Trigrams). When the Eight Trigrams interlock and interact, all things are born." Taiji contains Yin within Yang; the images of Liangyi show Yang dividing Yin. Yang cannot stand alone; it must rely on Yin to establish itself. Therefore, Yang takes Yin as its foundation, and Yin is the mother of Yang. Yin cannot manifest independently; it must await Yang to become visible. Therefore, Yin takes Yang as its commander, and Yang is the father of Yin. Rooted in both Yin and Yang, the principles of Heaven and Humanity are one. In terms of fixed positions, Yang is above and Yin is below, establishing the structure of opposing forms. In terms of Qi transformation, Yin rises and Yang descends, magnifying the function of dynamic circulation.
Let us discuss this using trigrams: Qian represents Heaven. To the left of Qian is Kan Water, and to the right is Dui Water. This indicates water moving in the sky, but it is not actual water; rather, it is the Yin Qi of water rising into the sky. If Yin rises to the sky without sufficient Qi transformation, dark mists will rise everywhere, altering the celestial phenomena. Kun represents Earth. To the left of Kun are Zhen Thunder/Fire, Xun Wind/Fire, and Li True Fire. This indicates fire emerging from underground, but it is not actual fire; rather, it is the Yang Qi of fire descending to the earth. If Yang descends to the earth without complete Qi circulation, the land becomes saline and barren, altering the terrestrial phenomena. However, discussing trigram images remains abstract; let us verify this through seasonal observations. Consider a year: after the Summer Solstice, intense heat prevails. If Yin Qi were not secretly generated and heavy rains did not fall periodically, the earth would turn to ashes. This is clear evidence of Yin Qi rising. Moreover, when Yin Qi rises to the sky and receives Heaven's distribution, it permeates boundlessly. After the Winter Solstice, cold condenses and freezes. If Yang Qi were not secretly stored and spring waters did not flow, people would freeze to death. This is clear evidence of Yang Qi descending. Furthermore, when Yang Qi descends to the earth and receives the earth's incubation, it develops infinitely. Specifically, Yin Qi does not rise by itself; it requires Yang Qi to ascend. The Yang Qi on earth is the Yang Qi that descended from heaven; assisting Yin's ascent with Yang, we speak of "Yin ascending" rather than "Yang ascending." Yang Qi does not descend vacuously; it must contain Yin Qi. The Yin Qi in heaven is the Yin Qi that rose from earth; transforming with Yang following Yin, we speak of "Yang descending" rather than "Yin descending." Thus, Yin and Yang are mutually rooted, originally one Qi, divided only by the movements of ascent and descent!
Speaking of humans: Human Yin Qi ascending refers to the essence and Qi derived from food and drink processed by the Spleen and Stomach, rising to the Lung. As the classics state, "Fluids enter the Stomach, overflow with essence and Qi, are transported upward to the Spleen, where the Spleen scatters the essence, transporting it upward to the Lung." This is like water moving in the sky. Since Qi contains Water, it is called Yin Ascending, yet Water never separates from Qi. If it is not the steaming of Qi and Water together, but rather pathogenic water flooding upward, water will overflow from high sources, leading to conditions such as Lung distension and wheezing cough. Since Qi and Water originate in the Stomach, the Stomach must be full of food and drink for Yin Qi to flourish. Hence, the classics say: "Essence Qi is born from Grain Qi." If the Stomach Qi itself becomes diseased, the source of transformation and generation is cut off. How can one expect the Kidney's grasping function to store Yang Qi securely? Human Yang Qi descending refers to the Yang Qi of the Lung descending to the Kidney, just as Heavenly Yang Qi hides in the Earth. This is like fire emerging from underground. Water is transformed by Qi, hence called Yang Descending, yet Qi never separates from Water. If it is not the moistening interaction of Qi and Water, but rather dry Yang descending, the Metal (Lung) will wither and Water (Kidney) will exhaust, leading to conditions such as consumptive cough and bone-steaming fever. Thus, Yang Qi cannot descend vacuously; it must contain Yin Qi. The True Yin of the Lung is the Yin Qi rising from the Spleen, Stomach, and Kidney. Only when the Yin Qi of the Spleen, Stomach, and Kidney rises to the Lung and receives the Lung's distribution can Yin Qi fill the entire body. The classics state: "The Kidney connects upward to the Lung." And again: "Without Yang, Yin cannot be generated; without Yin, Yang cannot transform."
However, the ascent and descent of Yin and Yang are invisible. Let us use a pot and steamer as an analogy. The water and grain in the pot represent Water; the fire under the pot represents Fire. The steam rising from the pot is Yang Qi; the moisture within the steam is Yin Qi. But only when the pot is full of water and grain, heated by the fire below, and covered by the lid above, can the moisture in the steam warm and nourish, steaming upward and spreading downward. Qi containing Water is Yin Ascending; Water transformed by Qi is Yang Descending. If the pot lacks water and grain, cooking without rice results in the fire beneath holding only deficient Yang, and the lid becoming a useless vessel. Or, if there is water and grain but no fire underneath, not only can essence and Qi not be steamed and transported, but even dregs cannot be melted; without a lid, not only is control lost, but spillover becomes uncontrollable. Are not Yin and Yang two Qi mutually dependent, inseparable even for a moment?
Weighing these two Qi, Yin receives Yang, and Yang commands Yin. Disease occurs if Yang Qi fails to reach even a fraction; death ensues if Yang Qi is exhausted even by a fraction. Therefore, humans should prioritize Yang Qi. Yet, while Yang Qi is important, Yin Qi is also crucial. Why? Human affairs and diseases often injure Yin. The classics say: "Stillness allows the Spirit to reside; movement leads to consumption." Daily toil involves movement; movement produces less than it consumes. Disease is also a form of movement; movement causes the Six Evils to transform into Fire. Transforming into Fire inevitably damages Yin, so in such cases, Yin Qi should be prioritized. For example, in sailing, the driving force is Qi, and the medium is Water; only with sufficient Water can Qi be vigorous. Similarly, consider a lamp: the flame is Fire, and the oil is Water; only with sufficient Oil can the Fire shine brightly. Qi is the commander of Blood, and Blood is the vessel for Qi. This is the principle that Yang commands Yin based on Yin. Without Yin, Yang has no basis and perishes. (Death occurs from the depletion of Yin fluids or the emaciation of large muscles.) Therefore, the term "Yin-Yang" is read as "Yin-Yang," not "Yang-Yin," which brings sudden enlightenment!