虚证宜补，实证宜泻，尽人而知之者。然或人虚而证实，如弱体之人，冒风伤食之类；
或人
实而证虚，如强壮之人，劳倦亡阳之类；或有人本不虚，而邪深难出；又有人已极虚，而外
邪尚伏。种种不同。若纯用补，则邪气益固；纯用攻，则正气随脱。此病未愈，彼病益深，
古方所以有攻补同用之法。疑之者曰∶两药异性，一水同煎，使其相制，则攻者不攻，补者
不补，不如勿服。若或两药不相制，分途而往，则或反补其所当攻，攻其所当补，则不惟
无益，而反有害，是不可不虑也。此正不然。盖药之性，各尽其能，攻者必攻强，补者必补
弱，犹掘坎于地，水从高处流下，必先盈坎而后进，必不反向高处流也。如大黄与人参同用
，大黄自能逐去是坚积，决不反伤正气；人参自能充益正气，决不反补邪气。盖古人制方之
法，分经别脏，有神明之道焉。如疟疾之小柴胡汤，疟之寒热往来，乃邪在少阳，木邪侮土
，中宫无主，故寒热无定。于是用柴胡以驱少阳之邪，柴胡必不犯脾胃；用人参以健中宫之
气，人参必不入肝胆。则少阳之邪自去，而中土之气自旺，二药各归本经也。如桂枝汤，桂
枝走卫以祛风，白芍走荣以止汗，亦各归本经也。以是而推，无不尽然。试以《神农本草》
诸药主治之说细求之，自无不得矣。凡寒热兼用之法，亦同此义，故天下无难治之症。后世
医者不明此理，药唯一途。若遇病情稍异，非顾此失彼，即游移浮泛，无往而非棘手之病矣
。但此必本于古人制方成法，而神明之。若竟私心自用，攻补寒热，杂乱不伦，是又杀人之
术也。
虚证适宜用补法，实证适宜用泻法，这是人人都知道的道理。然而，有的人身体虚弱而病邪实盛，比如体质瘦弱的人，感受风邪、饮食积滞之类；或者有的人身体强壮而正气虚衰，比如体格健壮的人，因过度劳累导致阳气耗脱之类；或者有人原本不虚，但病邪深入难以排出；又有人已经极度虚弱，但外邪仍然潜伏体内。情况种种不同。如果单纯使用补法，则邪气会更加固结；如果单纯使用攻法，则正气会随之脱失。这样不仅原来的病治不好，其他的病症也会加深，所以古方中有攻补兼用的方法。
怀疑的人说：“两种药物性质不同，放在同一锅水中煎煮，让它们相互制约，那么攻邪的药就不能攻邪，补虚的药就不能补虚，不如不服药。如果两种药物互不制约，分头发挥作用，那么就可能会反而补了应当攻除的病邪，攻除了应当保护的正气，这样不仅没有好处，反而有害，这是不得不考虑的问题。”这种观点完全不对。药物的本性，各自发挥其功效，攻邪的药必定攻击强盛的邪气，补虚的药必定补益虚弱的正气，就像在地上挖坑，水从高处流下，必定先填满低处的坑然后才继续前进，绝不会反向流向高处一样。比如大黄与人参同用，大黄自然能驱逐坚硬的积滞，决不会反过来伤害正气；人参自然能充养正气，决不会反过来补益邪气。大概古人制定方剂的方法，区分经络脏腑，其中有神妙变化的道理。比如治疗疟疾的小柴胡汤，疟疾的寒热往来，是因为邪气在少阳经，木邪侵犯土脏（脾胃），中焦失去主宰，所以寒热不定。于是用柴胡来驱散少阳经的邪气，柴胡必定不侵犯脾胃；用人参来健运中焦的气机，人参必定不进入肝胆。这样少阳的邪气自然去除，而中焦土气自然旺盛，两味药各归本经。比如桂枝汤，桂枝走卫分以祛风，白芍走营分以止汗，也是各归本经。由此类推，没有不是这样的。试着仔细探究《神农本草经》中各种药物的主治说法，自然没有不得到验证的了。凡是寒热并用的方法，也遵循同样的道理，所以天下没有难治的疾病。后世的医生不明白这个道理，用药只知单一途径。如果遇到病情稍有差异，不是顾此失彼，就是犹豫不决、浮泛不实，无处不是棘手的疾病了。但这必须基于古人制定方剂的成法，并且灵活变通运用。如果竟然凭私心自用，将攻补寒热杂乱无章地堆砌，这又是杀人的手段了。
Deficiency syndromes are suitable for tonification, and excess syndromes are suitable for purgation; this is known to everyone. However, there are cases where a person is deficient but the syndrome is excess, such as a frail individual contracting wind or suffering from food retention; or a person is robust but the syndrome is deficiency, such as a strong individual losing Yang Qi due to overexertion and fatigue; or someone who is originally not deficient, yet the pathogenic factor is deep and difficult to expel; again, someone who is extremely deficient, yet the external pathogen remains latent. These situations vary greatly. If one uses only tonification, the pathogenic factor becomes more entrenched; if one uses only purgation, the healthy Qi will follow in collapse. Thus, the original disease remains uncured, while other diseases deepen. This is why ancient formulas employ methods of combining attack (purgation) and tonification.
Those who doubt it say: "Two medicines have different natures; when decocted together in water, they mutually restrain each other. Consequently, the attacking medicine fails to attack, and the tonifying medicine fails to tonify. It is better not to take them. If the two medicines do not mutually restrain and act separately, then one might inadvertently tonify what should be attacked, or attack what should be tonified. This would not only be unbeneficial but harmful, which is a matter that must be considered." This view is entirely incorrect. The nature of each medicine fulfills its own function. The attacking medicine necessarily attacks the strong [pathogen], and the tonifying medicine necessarily tonifies the weak [healthy Qi]. This is like digging a pit in the ground; water flows down from a high place, filling the low pit first before continuing forward; it certainly does not flow back up to the high place. For example, when Dahuang (Rhei Radix et Rhizoma) and Renshen (Ginseng Radix et Rhizoma) are used together, Dahuang naturally expels the hard accumulation without injuring the healthy Qi; Renshen naturally supplements the healthy Qi without tonifying the pathogenic factor. Generally, the method by which ancients formulated prescriptions involves distinguishing meridians and zang-fu organs, possessing divine and subtle principles.
For instance, in Xiaochaihu Tang (Minor Bupleurum Decoction) for treating malaria, the alternating chills and fever result from the pathogen being in the Shaoyang (Lesser Yang) meridian. Wood pathogen insulting Earth (Spleen/Stomach), causing the Middle Jiao to lack a master, leads to indeterminate chills and fever. Therefore, Chaihu (Bupleuri Radix) is used to drive out the Shaoyang pathogen; Chaihu will not invade the Spleen and Stomach. Renshen (Ginseng Radix et Rhizoma) is used to strengthen the Qi of the Middle Jiao; Renshen will not enter the Liver and Gallbladder. Thus, the Shaoyang pathogen departs naturally, and the Middle Earth Qi prospers naturally; the two medicines return to their respective meridians. Similarly, in Guizhi Tang (Cinnamon Twig Decoction), Guizhi (Cinnamomi Ramulus) travels through the Wei (Defensive) level to dispel wind, and Baishao (Paeoniae Radix Alba) travels through the Ying (Nutritive) level to stop sweating; both also return to their respective meridians. By extrapolating from this, all cases are similar. One can carefully investigate the indications of various drugs in the Shennong Bencao Jing (Divine Farmer's Materia Medica) and find verification in every case. The principle of combining cold and hot therapies is the same; thus, there are no incurable diseases in the world.
Later physicians, failing to understand this principle, rely on a single approach to medication. When encountering slight variations in the condition, they either neglect one aspect for another, or hesitate and act superficially, resulting in every case becoming intractable. However, this must be based on the established methods of ancient formula formulation, applied with flexibility and insight. If one were to selfishly impose personal whims,杂乱ly mixing attack, tonification, cold, and heat without order, this would become a method of killing people.