以热治寒，以寒治热，谓之正治，又谓之逆治。（逆其性也。）以热治热，以寒治寒，
谓之反治，又谓之从治。（从其性也。）而有真反假反之分。假反者，如热邪内
陷，阳气不达于外，故身冷肢厥，战 恶寒，以大承气汤下之而愈。不识者，
见其外证似寒，用寒讶其相反。识者谓其内证真热，用寒实为正治，乃假反而
非真反也。真反者，如风火暴盛，痰涎上涌，闭塞咽喉，非辛热之品不能
开散，不得已，暂用星、半、乌、附、巴豆等热药，是则真反也。又有寒热并用者，
因其人寒热之邪夹杂于内，不得不用寒热夹杂之剂。古人每多如此。昧者訾为
杂乱，乃无识也。然亦有纯寒而于热剂中少加寒品，纯热而于寒剂中少加热药者，
此则名为反佐。以纯热证虽宜用纯寒，然虑火因寒郁，则不得不于寒剂中少佐辛热
之品，以行散之，庶免凝闭郁遏之患。（寒药热服，亦此意也。）纯寒证虽宜用纯热，然虑热
性上升，不肯下降，则不得不于热剂中少佐沉寒之品，以引热药下行，（如加胆汁、
童便入热药中，引入肝肾之类。又热药寒服，亦此意也。）此反佐之义也。知此诸义，则上病取下，
（如心火上炎，由肾水下虚，滋阴则火自降。）下病取上，（如小便不摄，由肺气虚者，则
益肺气。）左病取右，右病取左，（如左半身痰凝不遂，由右半身火气逼注使然，则泻右之
火气，而左自宽。）欲升先降，（浊降而后清可得而升，如水停气不化津而渴，用五苓去水
升清，则津生渴止是也。）欲降先升，（如小便不通用吐法。）欲行先止，（如气虚散漫，不
能营运，须先收敛其气，凝聚不散，盛则自运，所谓塞因塞用也。）欲止先行，（如食积，
泻用承气去积则已，所谓通因通用也。）等法，皆触类贯通矣。
用热性药治疗寒性病证，用寒性药治疗热性病证，称为正治法，又叫做逆治法。（即逆着病证的性质进行治疗。）用热性药治疗热性病证，用寒性药治疗寒性病证，称为反治法，又叫做从治法。（即顺从病证的假象进行治疗。）其中又有真反治和假反治的区别。所谓假反治，例如热邪内陷，阳气不能通达于体表，所以出现身体寒冷、四肢厥冷、战栗并厌恶寒冷的症状，使用大承气汤（Major Chengqi Decoction）攻下里实而痊愈。不认识此理的人，看到外表症状像寒证，认为用寒凉药与病情相反。认识此理的人则指出其内在本质是真热证，使用寒凉药实际上是正治法，这属于假反治而非真反治。所谓真反治，例如风火之邪突然亢盛，痰涎向上涌出，闭塞咽喉，非辛热性质的药物不能开散，不得已暂时使用天南星、半夏、乌头、附子、巴豆等热性药物，这才是真正的反治。又有寒热药并用的情况，因为患者体内寒热邪气夹杂，不得不使用寒热药混合的方剂。古人大多如此做法。无见识的人指责这是杂乱无章，那是没有学识的表现。然而也有纯寒证却在热性方剂中少量加入寒性药物，或纯热证却在寒性方剂中少量加入热性药物的情况，这被称为反佐法。对于纯热证虽然适宜使用纯寒性药物，但担心火热因受寒凉遏制而郁结，因此不得不在寒性方剂中少量佐以辛热药物，以宣行疏散，从而避免凝滞闭阻、郁遏的祸患。（寒性药物热服，也是这个意思。）对于纯寒证虽然适宜使用纯热性药物，但担心热性药势上升而不肯下行，因此不得不在热性方剂中少量佐以沉寒的药物，以引导热药下行，（例如在热药中加入胆汁、童便等，引入肝肾经之类。另外热性药物冷服，也是这个意思。）这就是反佐法的含义。懂得这些道理，那么“上病取下”（例如心火上炎，是由于肾水亏虚所致，滋养阴液则火势自然下降）、“下病取上”（例如小便失禁，是由于肺气虚弱，则补益肺气）、“左病取右，右病取左”（例如左侧半身痰凝导致活动不利，是由于右侧半身火气逼迫灌注所致，则泻右侧的火气，左侧自然宽松）、“欲升先降”（浊阴下降后清阳才能上升，例如水湿停聚导致气化不利、津液不布而口渴，使用五苓散去除水湿以提升清阳，则津液生成、口渴停止）、“欲降先升”（例如小便不通采用吐法）、“欲行先止”（例如气虚散漫，不能正常运化，必须先收敛其气，使其凝聚不散，气盛则自然运行，这就是“塞因塞用”法）、“欲止先行”（例如食积停滞，使用承气汤泻下去除积滞即可痊愈，这就是“通因通用”法）等等法则，都可以触类旁通、融会贯通了。
Treating cold conditions with heat, and treating heat conditions with cold, is called the **Correct Treatment** (Zheng Zhi), also known as the **Reverse Treatment** (Ni Zhi). (This involves acting against the nature of the disease.) Treating heat conditions with heat, and treating cold conditions with cold, is called the **Contrary Treatment** (Fan Zhi), also known as the **Following Treatment** (Cong Zhi). (This involves following the apparent nature of the disease.) There are distinctions between true contrary treatment and false contrary treatment. False contrary treatment: for example, when pathogenic heat sinks inward and Yang Qi fails to reach the exterior, causing coldness of the body, cold limbs, shivering, and aversion to cold, curing it by purging with **Da Cheng Qi Tang** (Major Order the Qi Decoction) constitutes a cure. Those who do not understand this see the external symptoms resembling cold and consider the use of cold medicine as contradictory. Those who understand recognize that the internal condition is truly heat; thus, using cold medicine is actually the Correct Treatment, which is false contrary rather than true contrary. True contrary treatment: for example, when wind-fire flares up violently, phlegm-saliva surges upward, blocking the throat, only pungent-hot substances can open and disperse it. Reluctantly, hot medicines such as **Tian Nan Xing** (Arisaematis Rhizoma Preparatum), **Ban Xia** (Pinelliae Rhizoma), **Wu Tou** (Aconiti Lateralis Radix Praeparata), **Fu Zi** (Aconiti Radix Praeparata), and **Ba Dou** (Crotonis Fructus) are temporarily used; this is true contrary treatment. There are also cases where cold and hot medicines are used together because the patient's interior contains mixed cold and hot pathogens, necessitating a formula containing both cold and hot ingredients. Ancients often did this. Ignorant people criticize this as chaotic, showing a lack of knowledge. However, there are also instances where a small amount of cold substance is added to a purely hot formula for a purely cold condition, or a small amount of hot medicine is added to a purely cold formula for a purely hot condition; this is called **Counter-Assistance** (Fan Zuo). For a purely hot condition, although purely cold medicine is appropriate, one must worry that fire may become depressed due to cold restraint; therefore, it is necessary to add a small amount of pungent-hot substances to the cold formula to promote dispersion, thereby avoiding the risk of stagnation, closure, and depression. (Taking cold medicine while hot is also based on this principle.) For a purely cold condition, although purely hot medicine is appropriate, one must worry that the ascending nature of heat will prevent it from descending; therefore, it is necessary to add a small amount of heavy-cold substances to the hot formula to guide the hot medicine downward (such as adding bile or child's urine to hot medicines to direct them to the Liver and Kidney meridians. Taking hot medicine while cold is also based on this principle). This is the meaning of Counter-Assistance. Understanding these principles allows one to master methods such as "treating upper diseases by targeting the lower" (e.g., Heart Fire flaming upward due to deficiency of Kidney Water; nourishing Yin causes the Fire to descend naturally); "treating lower diseases by targeting the upper" (e.g., incontinence due to Lung Qi deficiency; tonifying Lung Qi); "treating left-sided diseases by targeting the right, and right-sided diseases by targeting the left" (e.g., hemiplegia on the left side due to phlegm coagulation caused by Fire forcing its way into the right side; draining the Fire on the right relaxes the left); "to ascend, first descend" (after turbid Yin descends, clear Yang can ascend; e.g., thirst due to water retention and failure of Qi transformation to produce fluids; using **Wu Ling San** (Five-Ingredient Powder with Poria) to remove water and ascend clear Yang generates fluids and stops thirst); "to descend, first ascend" (e.g., using emesis for urinary retention); "to promote movement, first stop" (e.g., in Qi deficiency with scattering, unable to circulate; one must first converge the Qi so it gathers and does not scatter; when abundant, it moves naturally; this is the method of "treating obstruction with obstruction" [Se Yi Sai Yong]); "to stop, first promote movement" (e.g., food stagnation; using **Cheng Qi Tang** formulas to purge and remove stagnation cures it; this is the method of "treating flow with flow" [Tong Yin Yong Tong]). By understanding these, all methods can be comprehended through analogy and integration.