治寒以热，治热以寒，工所共知也，治寒以热而寒弥甚，治热以寒而热弥炽，殆未察五
脏有阴阳之性，各因其类而取之耳，经不云乎，寒之而热者取之阴，热之而寒者取之阳。假
有病热，施以寒剂，其热甚者，当益其肾，肾水既滋，热将自除，人有病寒，施以热剂，其
寒甚者，当益其心，心火既壮，寒将自已。此所谓察阴阳之性，因其类而取之也。经又曰∶
有者求之无者求之，盛者责之，虚者责之，于有无言求，于盛虚言责何耶。夫求者求其所以
治，与夫所以致益也，责者责其所当泻，与夫所宜补也，假有或热或寒，治须汗下。此所谓
有者求之，寒甚而热之，或不热，则致益其心，热甚而寒之或不寒，则致益其肾。此所谓无
者求之，假有心实生热，必泻其心，肾强生寒，必泻其肾，此所谓盛者责之，假有心虚多寒
，必补其心，肾虚多热，必补其肾。此所谓虚者责之，大抵五行之理，互有盛衰，而补泻消
长，在通其伦类而已。
病有小大，则以感于邪者。有浅有深，治有逆从，则以达于理者，有正有权，盖微者逆
之，逆者正治，此理之正也，甚者从之。从者反治，此理之权也。假有疾势未亟，要在折其
气而排去之，惟能知治寒以热，治热以寒，则相为制伏者，易为功。假有疾势过甚，要在顺
其性而调和之，惟能知热因寒用，寒因热用，则气体相求者，得其宜，且逆者正治，其为制
伏，自有差数，从者反治，则一同二异，二同三异，又有从少从多之不齐。然则裁制方剂者
，固宜深思之熟计之也。
用热性药治疗寒证，用寒性药治疗热证，这是医生们共同知晓的道理。但如果用热性药治疗寒证，寒邪反而更重；用寒性药治疗热证，热势反而更盛，这大概是没有考察五脏具有阴阳的属性，没有根据事物的同类性质来选取治疗方法罢了。医经不说过吗：“用寒凉药治疗而热不退的，应当从阴分入手治疗；用温热药治疗而寒不除的，应当从阳分入手治疗。”
例如，患有热病，使用寒凉药剂，如果热势严重，应当滋补肾阴（肾水）。肾水得到滋养，热邪自然消除。有人患有寒病，使用温热药剂，如果寒势严重，应当温补心阳（心火）。心火得到壮盛，寒邪自然停止。这就是所说的考察阴阳的属性，根据其同类性质来选取治疗方法。
医经又说：“有实邪的要探究其根源，无实邪的要探究其虚损；邪气盛的要责求其当泻之处，正气虚的要责求其当补之处。”为什么在“有无”上说要“求”，在“盛虚”上说要“责”呢？所谓“求”，是探求所以能治愈的原因，以及所以导致病情加重（益）的原因；所谓“责”，是责求其所应当泻除的，以及所应当补益的。
例如，有的表现为热或寒，治疗需要采用发汗或攻下的方法。这就是所说的“有者求之”。如果寒邪很盛却用热药治疗，结果并没有退热，那就是导致心火过亢（致益其心）；如果热邪很盛却用寒药治疗，结果并没有退热，那就是导致肾水亏虚（致益其肾）。这就是所说的“无者求之”。
例如，心气实证产生热邪，必须泻心；肾气强盛产生寒象，必须泻肾。这就是所说的“盛者责之”。例如，心气虚弱导致多寒，必须补心；肾气虚弱导致多热，必须补肾。这就是所说的“虚者责之”。
大抵五行的道理，互相之间有盛衰的变化，而补法、泻法、消法、长法，关键在于通晓其伦理类别关系而已。
疾病有轻重的不同，是因为感受邪气的程度不同。病位有浅有深，治疗有逆治和从治的区别，是因为通达医理的方式不同。治疗有正治和权变（反治），大概病情轻微的，采用逆治法，逆治就是正治，这是常理的正道；病情严重的，采用从治法，从治就是反治，这是常理的权变。
例如，疾病势头如果不急迫，关键在于挫败邪气并将其排出体外。只有懂得用热药治寒、用寒药治热的原理，利用相互制约的关系，才容易取得功效。例如，疾病势头过于严重，关键在于顺应病势并调和它。只有懂得“热因寒用”（以热药为君，佐以寒药）、“寒因热用”（以寒药为君，佐以热药）的原理，使药性与病气相求，才能得其适宜。
况且，逆治即正治，其制约作用自有等级差别；从治即反治，则有一同二异、二同三异等情况，又有从少与从多的不同。那么，制定方剂的人，固然应该深思熟虑啊。
Treating cold with heat and treating heat with cold is knowledge shared by all physicians. However, if treating cold with heat causes the cold to intensify, or treating heat with cold causes the heat to flare up further, it is likely that one has failed to examine the yin-yang nature of the five zang organs and has not selected treatments according to their respective categories. Does not the classic state: "If cooling treatment fails to resolve heat, seek it in yin; if warming treatment fails to resolve cold, seek it in yang."
For instance, in a case of febrile disease treated with cold-potent drugs, if the heat is severe, one should nourish the Kidney (Shen). Once the Kidney water is nourished, the heat will naturally dissipate. In a case of cold disease treated with hot-potent drugs, if the cold is severe, one should strengthen the Heart (Xin). Once the Heart fire is robust, the cold will naturally cease. This is what is meant by examining the nature of yin and yang and selecting treatments based on their categorical affinity.
The classic also states: "For excess, investigate the root; for deficiency, investigate the loss. For fullness, hold accountable for what needs purging; for emptiness, hold accountable for what needs tonifying." Why does it speak of "investigating" regarding existence/non-existence and "holding accountable" regarding fullness/emptiness? To "investigate" means to seek the reason for cure and the reason for iatrogenic harm (exacerbation). To "hold accountable" means to identify what ought to be purged and what ought to be tonified.
For example, when symptoms present as either heat or cold, treatment may require diaphoresis (sweating) or purgation. This corresponds to "investigating the excess." If cold is severe but warming treatment fails to reduce it, this results in an exacerbation of Heart fire. If heat is severe but cooling treatment fails to reduce it, this results in an exacerbation of Kidney deficiency. This corresponds to "investigating the deficiency."
For instance, if Heart excess generates heat, one must purge the Heart. If Kidney excess generates cold manifestations, one must purge the Kidney. This corresponds to "holding accountable for fullness." If Heart deficiency leads to excessive cold, one must tonify the Heart. If Kidney deficiency leads to excessive heat, one must tonify the Kidney. This corresponds to "holding accountable for emptiness."
Generally, the principles of the Five Elements involve mutual waxing and waning. Tonification, purgation, reduction, and growth depend on understanding their logical categories.
Diseases vary in severity due to differences in pathogenic invasion. Pathogens penetrate at varying depths. Treatments vary between contrary (ni) and following (cong) approaches depending on the mastery of medical principles. There are standard treatments (zheng) and flexible adaptations (quan). Mild conditions are treated by contraries; contrary treatment is standard treatment, which is the orthodox principle. Severe conditions are treated by followers; follower treatment is counter-treatment, which is the adaptive principle.
For example, if the disease momentum is not urgent, the goal is to break the qi and expel the pathogen. Understanding how heat treats cold and cold treats heat allows for mutual control, making efficacy easier to achieve. If the disease momentum is extreme, the goal is to follow the nature of the disease and harmonize it. Understanding "treating heat with cold administration" (using cold herbs as adjuvants to hot herbs) and "treating cold with heat administration" (using hot herbs as adjuvants to cold herbs) ensures that the drug nature seeks the pathogenic nature, achieving appropriateness.
Furthermore, contrary treatment (standard) has its own degrees of control. Following treatment (counter-treatment) involves variations such as "one same, two different" or "two same, three different," and disparities in the proportion of following agents. Therefore, those who formulate prescriptions must certainly deliberate deeply and plan carefully.