雷真君曰∶天地之道，不外阴阳，人身之病，又何能离阴阳也。内经论阴阳，已无余义。
然而止论其细微，反未论其大纲也。人身之阴阳，其最大者，无过气血，内经虽略言之，究
未尝言其至大也。盖气血之至大者，在气之有余与血之不足。气有余，则阳旺而阴消；血有
余，则阴旺而阳消。阳旺而阴消者，当补其血；阴旺而阳消者，当补其气。阳旺而阴消者，宜
泄其气；阴旺而阳消者，宜泄其血。欲阴阳补泻之宜，视气血之有余不足而已。
雷真君曰∶昼夜最可辨病之阴阳，然而最难辨也。阳病昼重而夜轻，谓阳气与病气交旺也，然亦
有阳病而昼不重者，盖阳气虚之故耳。阴病昼轻而夜重、阴气与病气交旺也，然亦有阴病而夜反轻
者，盖阴气虚之故耳。夫阳气与病气交旺者，此阳未虚之症，故元阳敢与邪气相争而不止，虽见之势
重，其实病反轻，当助其阳气以祛邪，不可但祛邪而不补其阳气也。阴气与病气交旺者，此阴未衰之
症，故真阴与邪气相战而不已，虽见之势横，其实病未甚也，助其阴气以逐邪，不必仅逐邪而不补其阴
气也。阳虚则昼不重，视其势若轻，而不知其邪实重。盖元阳虚极，不敢与阳邪相战，有退缩不
前之意，非阳旺而不与邪斗也。阴虚而夜反轻，视其势亦浅，而不知其邪实深。盖真阴微甚，不敢与
阴邪相犯，有趋避不遑之象，非阴旺而不与邪角也。此阴相辨于昼夜，不可为病之所愚。然而尚不可
拘于此也，或昼重而夜亦重，或昼轻而夜亦轻，或有时重，有时不重，或有时轻，有时不轻，此阴
阳之无定，而昼夜之难拘。又不可泥于补阳之说，当峻补于阴，而少佐其补阳之品，则阴阳有
养，而邪气不战自逃矣。
张真君曰∶论阴阳亦不能出经之微。
雷真君说：天地的规律，离不开阴阳，人体的疾病，又怎么能脱离阴阳呢？《内经》论述阴阳，已经没有遗漏的含义了。
然而，《内经》只论述了其细微之处，反而没有论述其大纲。人体内的阴阳，最大的方面，没有超过气血的，《内经》虽然简略地提到了，但终究没有言及其至大至重要的层面。大概气血中最重要的，在于气的有余和血的不足。气有余，则阳气旺盛而阴气消退；血有余，则阴气旺盛而阳气消退。对于阳气旺盛而阴气消退的情况，应当补益血液；对于阴气旺盛而阳气消退的情况，应当补益气。对于阳气旺盛而阴气消退的情况，适宜泄泻气；对于阴气旺盛而阳气消退的情况，适宜泄泻血。想要掌握阴阳补泻的适宜方法，只需观察气血是有余还是不足罢了。
雷真君说：昼夜最能辨别疾病的阴阳属性，然而也最难辨别。阳病在白天加重而在夜间减轻，这是因为阳气与病气相互交争而旺盛的缘故，但也有阳病在白天不加重的情况，这是因为阳气虚弱的缘故。阴病在白天减轻而在夜间加重，这是因为阴气与病气相互交争而旺盛的缘故，但也有阴病在夜间反而减轻的情况，这是因为阴气虚弱的缘故。所谓阳气与病气相互交争而旺盛的，这是阳气尚未虚弱的病症，所以元阳敢于与邪气相争而不止，虽然看起来病情严重，其实病反而轻浅，应当扶助阳气以祛除邪气，不能仅仅祛邪而不补益阳气。阴气与病气相互交争而旺盛的，这是阴气尚未衰弱的病症，所以真阴与邪气相战而不已，虽然看起来气势凶猛，其实病并不严重，应当助益阴气以驱逐邪气，不必仅仅驱逐邪气而不补益阴气。阳气虚弱则白天不加重，看其态势似乎轻浅，却不知道邪气实际上很重。因为元阳极度虚弱，不敢与阳邪相战，有退缩不前的意思，并非阳气旺盛而不与邪气争斗。阴气虚弱则夜间反而减轻，看其态势也显得浅显，却不知道邪气实际上很深。因为真阴非常微弱，不敢与阴邪相犯，有匆忙趋避的样子，并非阴气旺盛而不与邪气角力。这种通过昼夜来辨别阴阳的方法，不能被疾病的现象所愚弄。然而也不能拘泥于此，有的白天重夜间也重，有的白天轻夜间也轻，有时重有时不重，有时轻有时不轻，这是阴阳的不确定性，以及昼夜规律的难以拘守。又不可固执于补阳的说法，应当在滋阴时峻补阴液，同时少量佐以补阳的药物，那么阴阳得到滋养，邪气不战自逃了。
张真君说：论述阴阳也不能超出《内经》的精微之处。
Lei Zhenjun said: The principles of heaven and earth are none other than Yin and Yang; how can diseases of the human body depart from Yin and Yang? The *Neijing* (Classic of Internal Medicine) has exhaustively discussed Yin and Yang.
However, it only discusses the subtle details, failing to address the general outline. Among the Yin and Yang of the human body, the most significant are Qi and Blood. Although the *Neijing* briefly mentions them, it does not fully expound on their supreme importance. Generally, the most critical aspect of Qi and Blood lies in the excess of Qi and the deficiency of Blood. When Qi is in excess, Yang becomes vigorous while Yin declines; when Blood is in excess, Yin becomes vigorous while Yang declines. In cases where Yang is vigorous and Yin declines, one should tonify Blood; in cases where Yin is vigorous and Yang declines, one should tonify Qi. For conditions characterized by Yang excess and Yin decline, it is appropriate to drain Qi; for those with Yin excess and Yang decline, it is appropriate to drain Blood. To determine the appropriateness of tonifying or draining Yin and Yang, one need only observe whether Qi and Blood are in excess or deficient.
Lei Zhenjun said: Day and night are crucial for distinguishing the Yin and Yang nature of diseases, yet they are also the most difficult to distinguish. Yang-pattern diseases tend to worsen during the day and improve at night because Yang Qi and pathogenic Qi mutually intensify each other. However, there are Yang-pattern diseases that do not worsen during the day, due to the deficiency of Yang Qi. Yin-pattern diseases tend to improve during the day and worsen at night because Yin Qi and pathogenic Qi mutually intensify each other. However, there are Yin-pattern diseases that improve at night, due to the deficiency of Yin Qi. When Yang Qi and pathogenic Qi mutually intensify, this indicates a condition where Yang Qi is not yet deficient; thus, Yuan Yang (Primordial Yang) dares to contend with pathogenic Qi without ceasing. Although the symptoms appear severe, the disease is actually mild. One should assist Yang Qi to dispel pathogens rather than merely dispelling pathogens without tonifying Yang Qi. When Yin Qi and pathogenic Qi mutually intensify, this indicates a condition where Yin Qi is not yet depleted; thus, True Yin contends with pathogenic Qi incessantly. Although the presentation appears aggressive, the disease is not actually severe. One should assist Yin Qi to drive out pathogens rather than merely driving out pathogens without tonifying Yin Qi. When Yang Qi is deficient, symptoms do not worsen during the day; although the presentation seems mild, the pathogenic factor is actually substantial. This is because Yuan Yang is extremely deficient and dares not contend with Yang-type pathogens, showing a tendency to retreat rather than advance, which is not due to Yang being vigorous and refusing to fight. When Yin Qi is deficient, symptoms may improve at night; although the presentation seems superficial, the pathogenic factor is actually deep-seated. This is because True Yin is severely weak and dares not confront Yin-type pathogens, showing a hurried avoidance, which is not due to Yin being vigorous and refusing to engage. These distinctions based on day and night should not be deceived by the appearance of the disease. However, one must not rigidly adhere to these rules. Some diseases worsen both day and night, some improve both day and night, some fluctuate in severity, and some show no clear pattern. This reflects the indeterminacy of Yin and Yang and the difficulty in strictly applying day-night distinctions. One must not blindly adhere to theories of tonifying Yang alone; instead, one should vigorously tonify Yin while slightly assisting with Yang-tonifying herbs. In this way, Yin and Yang will be nourished, and pathogens will flee spontaneously without combat.
Zhang Zhenjun said: Discussions on Yin and Yang cannot transcend the subtleties found in the classics.