为人不可不知医，以命为重也，而命之所系，惟阴与阳，不识阴阳，焉知医理？此阴阳
之不可不论也。夫阴阳之体，曰干与坤；阴阳之用，曰水与火；阴阳之化，曰形与气。以生
杀言，则阳主生，阴主杀；以寒热言，则热为阳，寒为阴。若其生化之机，则阳先阴后，阳施
阴受。先天因气以化形，阳生阴也；后天因形以化气，阴生阳也。形即精也，精即水也；神
即气也，气即火也。阴阳二气，最不宜偏，不偏则气和而生物，偏则气乖而杀物。经曰∶阴
平阳秘，精神乃治；阴阳离决，精气乃绝。此先王悯生民之夭厄，因创明医道，以垂惠万世
者，在教人以察阴阳、保生气而已也。故内经于阴阳之理，惟恐人之不明，而切切谆谆，言
之再四。奈何后学，犹未能明，余请先言其二，而后言其一。夫二者阴也，后天之形也；一
者阳也，先天之气也。神由气化，而气本乎天，所以发生吾身者，即真阳之气也；形以精成，
而精生于气，所以成立吾身者，即真阴之气也。观上古天真论曰∶女子二七而后天癸至，男
子二八而后天癸至。非若阴生在后而阴成之难乎？又阴阳应象大论曰∶人年四十而阴气
自半也。非若阴衰在前而阴雕之易乎？所谓阴者，即吾之精而造吾之形也。夫无形则无
患，有形必有毁。故人生全盛之数，惟二八之后，以至四旬之外，前后止二十余年而形体渐
衰矣，此诚阴虚之象也。由此观之，即谓之阳道实、阴道虚若无不可。故丹溪引日月之盈
亏，以为阳常有余、阴常不足之论，而立补阴、大补等丸，以黄柏、知母为神丹，家传户用，其
害孰甚？殊不知天癸之未至，本由乎气；而阴气之自半，亦由乎气。是形虽在阴，而气则仍
从阳也。此死生之机，不可不辨。余所谓先言其二者，即此是也。何谓其一？一即阳也，
阳之为义大矣。夫阴以阳为主，所关于造化之原，而为性命之本者，惟斯而已。何以见之？
姑举其最要者，有三义焉∶一曰形气之辨，二曰寒热之辨，三曰水火之辨。夫形气者，阳化
气，阴成形，是形本属阴，而凡通体之温者，阳气也；一生之活者，阳气也；五官五脏之神明
不测者，阳气也。及其既死，则身冷如冰，灵觉尽灭，形固存而气则去，此以阳脱在前，而阴
留在后，是形气阴阳之辨也，非阴多于阳乎？二曰寒热者，热为阳，寒为阴；春夏之暖为阳，
秋冬之冷为阴。当长夏之暑，万国如炉，其时也，凡草木昆虫，咸苦煎炙；然愈热则愈繁，不
热则不盛。及乎一夕风霜，即僵枯遍野。是热能生物，而过热者惟病；寒无生意，而过寒则
伐尽。然则热无伤而寒可畏，此寒热阴阳之辨也，非寒强于热乎？三曰水火者，水为阴，火
为阳也。造化之权，全在水火，而水火之象有四，则日为太阳，火为少阳，水为太阴，月为少
阴，此四象之真形而人所未达也。余言未竟，适一耽医之客过余者，闻而异之曰∶月本太
阴，火岂少阳？古无是说，何据云然？亦有所谓乎？曰∶阳主乎外，阴主乎内，此阴阳之定
位也；阳中无太阴，阴中无太阳，此阴阳之专主也。日丽乎天，此阳中之阳也，非太阳乎？
月之在天，阳中之阴也，非少阴乎？水行于地，阴中之阴也，非太阴乎？火之在地，阴中之
阳也，非少阳乎？此等大义，诚丹溪所未知，故引日月盈亏，以证阴阳虚实。亦焉知水大于
月，独不虑阳之不足、阴之太过乎？客曰∶阴阳太少之说，固若有理；至于水大于月，便是阴
之有余，则凡天下之火不少也，阳岂独在于日乎？曰∶是更有妙理存也。夫阴阳之性，太者
气刚，故日不可灭，水不可竭，此日为火之本，水为月之根也；少者气柔，故火有时息，月有
时缺，此火是日之余，月是水之余也。惟其不灭者，方为真火；而时作时止者，岂即元阳？
故惟真阳之火，乃能生物；而燎原之凡火，但能焦物病物。未闻有以烘炙而生物者，是安可
以火喻日也？客曰∶若如此言，则水诚太阴矣；然何以云天一生水？水非阳乎？又何以云
水能生万物，水非生气乎？曰∶此问更妙。夫天一者，天之一也，一即阳也，无一则止于六
耳。故水之生物者，赖此一也；水之化气者，亦赖此一也。不观乎春夏之水，土得之而能生
能长者，非有此一乎？秋冬之水，土得之而不生不长者，非无此一乎？不惟不生而自且为
冻，是水亦死矣。可见水之所以生，水之所以行，孰非阳气所主？此水中有阳耳，非水即为
阳也。客曰∶然则生化之权，皆由阳气，彼言阳有余者，诚非谬也，而子反虑其不足，非过虑
乎？曰∶余为此论，正为此耳。惟恐人之不悟，故首言形气，次言寒热，此言水火，总欲辨明
阳非有余，不可罔顾之义。夫阳主生，阴主杀。凡阳气不充，则生意不广，而况于无阳乎？
故阳惟畏其衰，阴惟畏其盛，非阴能自盛也，阳衰则阴盛矣。凡万物之生由乎阳，万物之死
亦由乎阳，非阳能死物也，阳来则生，阳去则死矣。试以太阳证之，可得其象。夫日行南
陆，在时为冬，斯时也，非无日也，第稍远耳，便见严寒难御之若此，万物凋零之若此。然则
天地之和者，惟此日也；万物之生者，亦惟此日也。设无此日，则天地虽大，一寒质耳，岂非
六合尽冰壶，乾坤皆地狱乎？人是小乾坤，得阳则生，失阳则死。阳衰者，即亡阳之渐也；
恃强者，即致衰之兆也。可不畏哉！故伏羲作易，首制一爻，此立元阳之祖也。文王衍易，
凡六十四卦，皆以阳喻君子，阴喻小人，此明阳气之德也。干之彖曰∶大哉干元，万物资始，
乃统天。此言元贯四德，阳为发育之首也。坤之初六曰∶履霜坚冰至。此虑阴之渐长，防
其有妨化育也。大有之彖曰∶大有元亨，火在天上。此言阳德之亨，无所不照也。系辞曰∶
天地之大德曰生。此切重生生之本也。内经曰∶凡阴阳之要，阳密乃固。此言阴之所恃
者，惟阳为主也。又曰∶阳气者若天与日，失其所则折寿而不彰，故天运当以日光明。此言
天之运，人之命，元元根本，总在太阳无两也。凡此经训，盖自伏羲、黄帝、文王、岐伯、周
公、孔子，六大圣人，千古相传，若出一口，岂果余之私虑哉？由此言之，可见天之大宝，只
此一丸红曰；人之大宝，只此一息真阳。孰谓阳常有余，而欲以苦寒之物，伐此阳气，欲保
生者，可如是乎？客曰∶至哉！余得闻所生之自矣。然既有其道，岂无其法，欲固此阳，计
从安出？曰∶但知根本，即其要也。曰∶何为根本？曰∶命门是也。曰∶余闻土生万物，故脾
胃为五脏六腑之本；子言命门，余未解也。曰∶不观人之初生，生由脐带，脐接丹田，是为气
海，即命门也。所谓命门者，先天之生我者，由此而受；后天之我生者，由此而栽也。夫生
之门即死之户，所以人之盛衰安危，皆系于此者，以其为生气之源，而气强则强，气衰则病，
此虽至阴之地，而实元阳之宅。若彼脾胃者，乃后天水谷之本，犹属元阳之子耳。子欲知
医，其母忽此所生之母焉。言难尽意，请再着真阴论以悉之何如？客忻然曰∶愿再闻其义。
人不可不学习医学，因为生命是最为重要的，而生命的维系，关键在于阴与阳。如果不了解阴阳，又怎能懂得医理呢？这就是阴阳不可不探讨的原因。
从本体来说，阴阳对应于乾卦和坤卦；从作用来说，阴阳对应于水和火；从化生过程来说，阴阳对应于形和气。从生杀的角度来看，阳气主生长，阴气主肃杀；从寒热的角度来看，热属于阳，寒属于阴。至于其生化之机，则是阳气先行发动，阴气随后接受。先天阶段，因气而化生为形，这是阳生阴；后天阶段，因形而化生为气，这是阴生阳。形就是精，精就是水；神就是气，气就是火。阴阳二气，最忌讳偏颇，不偏则气和顺而能化生万物，偏则气乖逆而能杀伤万物。《内经》说：“阴气平和，阳气固密，精神就能正常；如果阴阳分离决裂，精气就会断绝。”这先代圣王怜悯百姓遭受夭折之苦，因此创立并阐明医道，以惠及万世，其核心在于教导人们观察阴阳、保养生气罢了。所以《黄帝内经》在论述阴阳之理时，唯恐人们不明白，反复恳切地谆谆告诫。无奈后学者，仍然不能明白，我打算先讲两个方面（指阴/形），然后再讲一个方面（指阳/气）。那两个方面属阴，是后天的形体；那一个方面属阳，是先天的元气。神由气化生，而气本源于天，所以发生我们身体的，就是真阳之气；形体由精构成，而精生于气，所以成立我们身体的，就是真阴之气。看《上古天真论》说：“女子十四岁后天癸至，男子十六岁后天癸至。”这不正是说明阴在后天生成且难以成就吗？又看《阴阳应象大论》说：“人四十岁时，阴气就减半了。”这不正是说明阴气衰退在前且容易凋谢吗？所谓的阴，就是我的精，它造就我的形体。没有形体就没有祸患，有了形体必然会有毁坏。所以人处于全盛状态的时期，只有从十六岁之后，到四十岁之外，前后不过二十多年，形体就开始逐渐衰败了，这确实是阴虚的表现。由此看来，即使说是“阳道实、阴道虚”也没什么不可以的。所以朱丹溪引用月亮的盈亏，提出“阳常有余、阴常不足”的理论，并创立了补阴丸、大补丸等方剂，将黄柏、知母视为神丹，家家传用，这种危害难道不是很大吗？殊不知天癸的未至，本来是由气决定的；而阴气的自半，也是由气决定的。虽然形体属于阴，但气仍然归属于阳。这是生死的关键，不可不辨明。我所说的先讲那两个“二”，就是指这个。那么什么是“一”呢？“一”就是阳，阳的意义非常宏大。阴以阳为主导，关系到造化的本源，作为性命的根本，只有这一点而已。怎么证明呢？姑且列举最重要的三点：一是形与气的辨别，二是寒与热的辨别，三是水与火的辨别。所谓形气，阳化气，阴成形，所以形本属阴，而凡全身温暖的，是阳气；凡生命活跃的，是阳气；五官五脏神明变化莫测的，是阳气。等到人死后，身体冷如冰，灵觉完全消失，形体固然还在，但气已经离去，这是阳脱在前，阴留在后，这就是形气阴阳的辨别，难道不是阴多于阳吗？二是寒热，热为阳，寒为阴；春夏的温暖为阳，秋冬的寒冷为阴。正值长夏酷暑，天下如炉，这个时候，凡是草木昆虫，都苦于煎熬；然而越热就越繁茂，不热就不兴盛。等到一夜风霜，就僵枯遍野。这说明热能生物，但过热则致病；寒无生机，但过寒则砍伐殆尽。既然如此，热无伤而寒可畏，这就是寒热阴阳的辨别，难道不是寒强于热吗？三是水火，水为阴，火为阳。造化的权柄，全在水火，而水火的现象有四类，即日为太阳，火为少阳，水为太阴，月为少阴，这是四象的真实形态，是人们所未能通达的。我的话还没说完，恰好一位沉迷医学的客人经过我这里，听到后感到惊奇，说：“月亮本是太阴，火难道是少阳？古代没有这种说法，有什么依据这样说呢？也有什么讲究吗？”我说：“阳主外，阴主内，这是阴阳的固定位置；阳中没有太阴，阴中没有太阳，这是阴阳的专主属性。太阳附丽于天空，这是阳中之阳，不就是太阳吗？月亮悬挂在天，这是阳中之阴，不就是少阴吗？水行于大地，这是阴中之阴，不就是太阴吗？火存在于地下，这是阴中之阳，不就是少阳吗？这些大义，确实是朱丹溪所不知道的，所以他引用日月盈亏来论证阴阳虚实。他又怎知道水大于月，独独不考虑阳的不足、阴的太过呢？”客人说：“阴阳太少之说，确实好像有理；至于水大于月，就是阴有余，那么天下的火也不少，阳难道只存在于日中吗？”我说：“这里还有更妙的道理存在。阴阳的性质，太者气刚，所以日不可灭，水不可竭，这是日为火之本，水为月之根；少者气柔，所以火有时熄灭，月有时缺憾，这是火是日之余，月是水之余。只有不灭的，才是真火；时而发作时而停止的，难道是元阳吗？所以只有真阳之火，才能生物；而燎原的凡火，只能焦物病物。没听说过有通过烘烤炙烤来生物的，这怎么能用火来比喻日呢？”客人说：“如果像这样所说，那么水确实是太阴了；但是为什么说‘天一生水’？水不是阳吗？又为什么说‘水能生万物’，水不是生气吗？”我说：“这个问题更妙。所谓天一，是天之一，一就是阳，如果没有一，就止于六了。所以水能生物，依赖的是这一；水能化气，也依赖的是这一。不看春夏的水，土得到它就能生长，不是因为有这一吗？秋冬的水，土得到它却不生不长，不是因为没有这一吗？不仅不生而且自己冻结，水也就死了。可见水之所以生，水之所以行，哪一点不是阳气所主导？这是水中含有阳，并不是水本身就是阳。”客人说：“既然这样，生化的权柄，都由阳气决定，那些说阳有余的人，确实没有错，而你反而担心其不足，不是多虑了吗？”我说：“我写这篇论述，正是为此。唯恐人们不明白，所以首先讲形气，其次讲寒热，这里讲水火，总想辨明阳并非有余，不可不顾及的根本意义。阳主生，阴主杀。凡是阳气不充盛，则生机不广大，更何况是没有阳呢？所以阳只害怕衰弱，阴只害怕盛极，并非阴能自行盛极，而是阳衰则阴盛了。凡是万物的生存由于阳，万物的死亡也由于阳，并非阳能杀死物体，而是阳来则生，阳去则死。试着用太阳来验证，就可以得到形象。太阳运行到南陆，在季节上是冬天，这个时候，并非没有太阳，只是稍微远一些，就见到严寒难御到了这种地步，万物凋零到了这种地步。那么天地和谐的东西，只有这个太阳；万物的生存，也只有这个太阳。假如没有这个太阳，那么天地虽然大，也不过是一团寒气罢了，岂不是六合尽是冰壶，乾坤皆是地狱吗？人是小乾坤，得阳则生，失阳则死。阳气衰微，就是亡阳的开始；倚仗强壮，就是导致衰败的征兆。能不畏惧吗！所以伏羲作《易》，首先制定一爻（阳爻），这是确立元阳的祖始。文王推演《易》，凡六十四卦，都用阳比喻君子，用阴比喻小人，这是阐明阳气的德行。《干卦》彖辞说：‘伟大啊，乾元，万物依靠它开始，统率天道。’这是说元贯通四德，阳是发育的首要。《坤卦》初六爻辞说：‘踩上霜，坚冰就要来了。’这是忧虑阴气渐长，防止其妨碍化育。《大有卦》彖辞说：‘大有元亨，火在天上。’这是说阳德的亨通，无所不照。《系辞》说：‘天地的大德叫做生。’这是切中重视生生之本。《内经》说：‘凡是阴阳的要领，阳气致密然后阴气固守。’这是说阴所依赖的，只有阳为主宰。又说：‘阳气就像天和日，失去其所则减寿而不显扬，所以天的运行应当以日的光明为喻。’这是说天的运行，人的性命，根本根本，总在太阳独一无二。所有这些经典训诫，大概自从伏羲、黄帝、文王、岐伯、周公、孔子，这六位圣人，千古相传，如同出自一口，难道真的是我个人的私虑吗？由此而言，可见天的最大宝贝，只是这一轮红日；人的最大宝贝，只是这一息真阳。谁说阳常有余，而想用苦寒之物，来伐损这个阳气，想要保生的，可以这样做吗？”客人说：“太好了！我听到了生命的来源。既然有了这个道，难道没有法吗？想要固护这个阳，计策从哪里出？”我说：“只要知道根本，就是关键所在。”问：“什么是根本？”答：“命门就是。”问：“我听说土生万物，所以脾胃是五脏六腑的根本；您说命门，我不理解。”答：“不看人刚出生时，生命来自脐带，脐连接丹田，这叫气海，也就是命门。所谓命门，先天生成我的，由此承受；后天我生成的，由此栽培养育。生的门也就是死的户，所以人的盛衰安危，都系于此，因为它作为生气的源头，气强则身强，气衰则生病，这虽然是至阴之地，但实际上是元阳的宅邸。至于脾胃，乃是后天水谷的根本，还属于元阳的儿子罢了。您想学医，如果忽略了这个所生的母亲，那就麻烦了。言语难以尽意，请再写《真阴论》来详尽说明如何？”客人高兴地说：“愿意再听其中的义理。”
One must not be ignorant of medicine, for life is of the utmost importance. The sustenance of life depends solely on Yin and Yang; without understanding Yin and Yang, how can one comprehend medical principles? This is why Yin and Yang cannot but be discussed.
In terms of substance, Yin and Yang correspond to Qian (Heaven) and Kun (Earth); in terms of function, they correspond to Water and Fire; in terms of transformation, they correspond to Form and Qi. From the perspective of generation and destruction, Yang governs generation, while Yin governs destruction. From the perspective of cold and heat, heat belongs to Yang, and cold belongs to Yin. Regarding the mechanism of generation and transformation, Yang acts first and Yin receives subsequently. In the pre-heaven stage, form is transformed from Qi, which is Yang generating Yin; in the post-heaven stage, Qi is transformed from form, which is Yin generating Yang. Form is Jing (Essence), and Jing is Water; Shen (Spirit) is Qi, and Qi is Fire. The two Qi of Yin and Yang should most preferably not be biased. If unbiased, Qi is harmonious and generates things; if biased, Qi is discordant and destroys things. The Classics state: "When Yin is peaceful and Yang is secure, Spirit and Mind are regulated; when Yin and Yang separate and break apart, Essence and Qi are exhausted." The ancient kings, pitying the premature deaths of the people, therefore established and clarified the Way of Medicine to benefit all generations, teaching people to observe Yin and Yang and preserve the vital Qi. Thus, in the *Huangdi Neijing* (Yellow Emperor's Inner Canon), regarding the principles of Yin and Yang, it fears that people may not understand, repeatedly and earnestly admonishing them. Alas, later students still fail to understand. I propose to first speak of the "two" (referring to Yin/Form) and then speak of the "one" (referring to Yang/Qi). The "two" belong to Yin, representing post-heaven form; the "one" belongs to Yang, representing pre-heaven Qi. Shen arises from Qi transformation, and Qi originates from Heaven; thus, what generates our body is the True Yang Qi. Form is constituted by Jing, and Jing is born from Qi; thus, what establishes our body is the True Yin Qi. Observing the chapter *Shanggu Tianzhen Lun* (Discourse on the Heavenly Truth of Antiquity): "At fourteen, the Tian Gui (heavenly water/menstruation) arrives in women; at sixteen, it arrives in men." Does this not indicate that Yin is generated later and is difficult to complete? Furthermore, observing the chapter *Yinyang Yingxiang Dalun* (Great Discourse on the Correspondences between Yin-Yang and Phenomena): "At forty years of age, Yin Qi is halved." Does this not indicate that Yin declines early and is easily withered? The so-called Yin refers to my Jing, which creates my form. Without form, there is no disaster; with form, there must be decay. Therefore, the period of peak vitality in human life is only from sixteen onwards to beyond forty, lasting merely over twenty years before the form gradually declines. This is indeed a sign of Yin deficiency. From this perspective, even stating that "the Path of Yang is solid/excess, and the Path of Yin is deficient/empty" would be acceptable. Therefore, Zhu Danxi, citing the waxing and waning of the moon, proposed the theory that "Yang is often in excess, and Yin is often deficient," establishing formulas such as *Buyin Wan* (Nourish Yin Pill) and *Dabu Wan* (Great Tonify Pill), treating Huangbai (Phellodendri Cortex) and Zhimu (Anemarrhenae Rhizoma) as divine elixirs, used in every household. Is not the harm caused by this severe? Little do they know that the non-arrival of Tian Gui originally depended on Qi; and the halving of Yin Qi also depended on Qi. Although form belongs to Yin, Qi still follows Yang. This is the pivot of life and death, which must not fail to be distinguished. What I mean by speaking of the "two" first is precisely this. What is meant by the "one"? The "one" is Yang. The significance of Yang is great. Yin is governed by Yang; what concerns the origin of creation and serves as the root of life and nature is nothing other than this. How can we see this? Let us briefly mention three most important points: First, the distinction between Form and Qi; Second, the distinction between Cold and Heat; Third, the distinction between Water and Fire. Regarding Form and Qi: Yang transforms into Qi, Yin forms into shape. Thus, shape fundamentally belongs to Yin, while the warmth throughout the entire body is Yang Qi; the vitality of life is Yang Qi; the mysterious and unfathomable spirit of the five Zang organs and five sense organs is Yang Qi. After death, the body becomes cold as ice, and spiritual awareness is completely extinguished. The form remains, but the Qi has departed. This shows that Yang departs first, and Yin remains later. This is the distinction between Form, Qi, Yin, and Yang—is it not true that Yin exceeds Yang? Second, regarding Cold and Heat: Heat is Yang, Cold is Yin; the warmth of Spring and Summer is Yang, the cold of Autumn and Winter is Yin. During the intense heat of late summer, the world is like a furnace. At this time, all grasses, trees, insects, and animals suffer from scorching heat. Yet, the hotter it is, the more flourishing they become; without heat, they do not thrive. But after a night of wind and frost, they stiffen and wither across the fields. This shows that heat can generate life, but excessive heat causes disease; cold has no generative power, but excessive cold destroys everything. Therefore, heat does little harm, while cold is to be feared. This is the distinction between Cold, Heat, Yin, and Yang—is it not true that Cold is stronger than Heat? Third, regarding Water and Fire: Water is Yin, Fire is Yang. The power of creation lies entirely in Water and Fire. The manifestations of Water and Fire have four aspects: the Sun is Taiyang (Greater Yang), Fire is Shaoyang (Lesser Yang), Water is Taiyin (Greater Yin), and the Moon is Shaoyin (Lesser Yin). These are the true forms of the Four Images, which people have not yet comprehended. Before I could finish speaking, a guest obsessed with medicine passed by me. Hearing this, he was surprised and said: "The Moon is inherently Greater Yin; how can Fire be Lesser Yang? There is no such saying in antiquity. On what basis do you say this? Is there some principle involved?" I replied: "Yang governs the exterior, Yin governs the interior; this is the fixed position of Yin and Yang. There is no Greater Yin within Yang, and no Greater Yang within Yin; this is the exclusive dominion of Yin and Yang. The Sun attached to the sky is Yang within Yang, which is indeed Taiyang. The Moon hanging in the sky is Yin within Yang, which is indeed Shaoyin. Water flowing on the earth is Yin within Yin, which is indeed Taiyin. Fire existing within the earth is Yang within Yin, which is indeed Shaoyang. These great principles were indeed unknown to Zhu Danxi, who cited the waxing and waning of the sun and moon to prove the excess and deficiency of Yin and Yang. How could he know that since Water is greater than the Moon, one should not worry about the insufficiency of Yang and the excess of Yin?" The guest said: "The theory of Greater and Lesser Yin and Yang seems reasonable; however, since Water is greater than the Moon, implying an excess of Yin, there is plenty of fire in the world. Is Yang found only in the Sun?" I said: "There is an even more subtle principle here. The nature of the 'Greater' aspect is rigid Qi; thus, the Sun cannot be extinguished, and Water cannot be dried up. The Sun is the root of Fire, and Water is the root of the Moon. The 'Lesser' aspect has soft Qi; thus, Fire sometimes rests, and the Moon sometimes wanes. Fire is the remnant of the Sun, and the Moon is the remnant of Water. Only that which does not extinguish is True Fire; that which comes and goes intermittently, is it truly Yuan Yang (Primal Yang)? Therefore, only True Yang Fire can generate life, while ordinary fires that burn wildly can only scorch and damage things. It has never been heard that life is generated by roasting or baking. How can Fire be used to metaphorize the Sun?" The guest said: "If this is so, then Water is indeed Greater Yin. However, why does it say 'Heaven One generates Water'? Is Water not Yang? And why does it say 'Water can generate all things'? Is Water not the Qi of generation?" I said: "This question is even more profound. 'Heaven One' refers to the One of Heaven; One is Yang. Without One, it stops at Six. Therefore, what allows Water to generate things relies on this One; what allows Water to transform into Qi also relies on this One. Do you not observe that in Spring and Summer, when Earth obtains Water, it can grow and flourish? Is it not because of this One? In Autumn and Winter, when Earth obtains Water, it does not grow or flourish. Is it not because this One is absent? Not only does it not grow, but it freezes itself, meaning Water dies. Thus, it is evident that whatever makes Water generate and flow is dominated by Yang Qi. This means Yang exists within Water; it does not mean Water itself is Yang." The guest said: "Then, if the power of generation and transformation all stems from Yang Qi, those who say Yang is in excess are indeed correct. Why do you worry about its insufficiency? Is this not an overconcern?" I said: "I wrote this treatise precisely for this reason. Fearing that people might not realize this, I first spoke of Form and Qi, then of Cold and Heat, and now of Water and Fire, all to clarify that Yang is not in excess and that one must not ignore its fundamental importance. Yang governs generation, Yin governs destruction. Whenever Yang Qi is insufficient, the scope of generative power is narrow, let alone when there is no Yang. Therefore, Yang fears only decline, and Yin fears only excess. Yin cannot become excessive on its own; it becomes excessive because Yang declines. All things live due to Yang, and all things die due to Yang. It is not that Yang kills things; rather, when Yang comes, there is life; when Yang leaves, there is death. Let us use the Sun as proof to visualize this. When the Sun travels through the Southern Land, corresponding to Winter, although the Sun is present, it is slightly farther away, resulting in unbearable cold and the withering of all things. Thus, the thing that harmonizes Heaven and Earth is the Sun; the thing that generates all things is also the Sun. If there were no Sun, despite the vastness of Heaven and Earth, it would merely be a mass of cold. Would not the six directions be full of ice pots, and the universe a hell? Humans are a microcosm of Heaven and Earth; gaining Yang brings life, losing Yang brings death. Decline in Yang is the gradual onset of Yang collapse; relying on strength is the omen of leading to decline. Can one not fear this? Therefore, when Fuxi created the *I Ching* (Book of Changes), he first formulated one line (the Yang line), establishing the ancestor of Yuan Yang. When King Wen expanded the *I Ching*, in all sixty-four hexagrams, he used Yang to symbolize the gentleman and Yin to symbolize the petty person, clarifying the virtue of Yang Qi. The *Tuan Zhuan* (Commentary on the Decision) of Qian states: 'Great is the Primal Power of Qian! By it all things begin, and it commands Heaven.' This says that the Primal penetrates the four virtues, and Yang is the head of development. The *Yao Ci* (Line Statement) of the first Yin line of Kun states: 'Treading on frost, firm ice arrives soon.' This worries about the gradual growth of Yin, preventing it from hindering generation and cultivation. The *Tuan Zhuan* of Dayou states: 'Great Possession, Supreme Success. Fire is in the sky.' This says the prosperity of Yang virtue shines everywhere. The *Xici* (Great Commentary) states: 'The great virtue of Heaven and Earth is called Generation.' This emphasizes the root of continuous generation. The *Neijing* states: 'The essence of all Yin and Yang is that Yang must be dense/sealed for Yin to be secure.' This says that what Yin relies upon is solely Yang as the master. It also states: 'Yang Qi is like Heaven and the Sun; if it loses its proper place, lifespan is shortened and brilliance is obscured. Therefore, the movement of Heaven should be illuminated by the Sun.' This says that the movement of Heaven and the destiny of humans, the primal roots, lie entirely in the uniqueness of the Great Sun. All these classic teachings, passed down from the six sages—Fuxi, Yellow Emperor, King Wen, Qibo, Duke of Zhou, and Confucius—for millennia, as if coming from one mouth, are surely not merely my private concern? From this, we can see that the greatest treasure of Heaven is but this red Sun; the greatest treasure of Man is but this breath of True Yang. Who says Yang is often in excess? Those who wish to preserve life should not use bitter-cold substances to attack this Yang Qi. Can preservation of life be achieved thus?" The guest said: "Excellent! I have heard the source of my being. Since there is this Dao, is there not a method? To consolidate this Yang, where should the strategy come from?" I said: "Knowing the root is the key." He asked: "What is the root?" I answered: "Mingmen (Gate of Life)." He said: "I have heard that Earth generates all things, so Spleen and Stomach are the root of the five Zang and six Fu organs. You speak of Mingmen; I do not understand." I said: "Do you not observe that at birth, life comes via the umbilical cord, which connects to the Dantian, called Qihai (Sea of Qi), which is also Mingmen. So-called Mingmen: what generated me in pre-heaven is received from here; what I generate in post-heaven is cultivated from here. The gate of life is also the door of death. Therefore, the rise and fall, safety and danger of humans are all tied to this, because it is the source of vital Qi. Strong Qi leads to strength; weak Qi leads to illness. Although this is a place of extreme Yin, it is actually the residence of Yuan Yang. As for Spleen and Stomach, they are the root of post-heaven grain and water, belonging merely to the children of Yuan Yang. If you wish to know medicine, and neglect this mother that gave birth to you, it will be problematic. Words cannot fully express the meaning. Shall I write another treatise, *Zhenyin Lun* (Discourse on True Yin), to elaborate further?" The guest joyfully said: "I am willing to hear the principles again."