有表而热者，谓之表热。无表而热者，谓之里热。故苦以治五脏，五脏属阴而居于内，
辛者以治六腑，六腑属阳而居于外，故曰内者下之，外者发之。
饮食劳倦，为内伤元气。元气伤，则真阳下陷，内生虚热。故东垣发补中益气之论，用
人参、黄 等甘温之药，大补其气而提其下陷，此用气药以补气之不足者也。劳心好色，内伤真
阴
，用四物加黄柏、知母，补其阴而火自降，此用血药以补血之不足者也。益气、补阴，皆内
伤症也。一则因阳气之下陷而升提之，一则因阴火之上升而滋降之，一升一降，迥然不同矣
平日发热，热在行阳之分，肺气主之，故用白虎汤以泻气中之火。日晡潮热，热在行阴
之分
骨皮散治脉弦，故举之，使春气得以上升也。
治热之法有五∶一曰和，二曰取，三曰从，四曰折，五曰夺。假令小热之病，当以凉药
和之
。和之不已，次用取，为热势稍大，当以寒药取之。取之不已，次用从，为热势既甚，当以
温药从之。谓药气温也，味随所为。或以寒因热用，味通所用；或寒以温用，或以汗发之。
不已，又用折，为病势极甚，当以逆制之。制之不已，当以下夺之。下夺之不已，又用属，
为求其属以衰之。缘热深陷在骨髓，无法可出，针药所不能及，故求属以衰之。求属之法，
是同声相应，同气相求之道也。如或又不已，当广求其法而治之。譬如孙子之用兵，在山谷
，则塞渊泉；在水陆，则把渡口；在平川广野，当清野千里。塞渊泉者，刺俞穴。把渡口者
，夺病发时前。清野千里，如肌羸瘦弱，当广服大药以养正。
有表证而发热的，称为表热。没有表证而发热的，称为里热。因此，苦味药用于治疗五脏，因为五脏属阴且位于体内；辛味药用于治疗六腑，因为六腑属阳且位于体表，所以说内部病证用攻下法，外部病证用发汗法。
饮食不节和过度劳累，会内伤元气。元气受损，则真阳下陷，体内产生虚热。所以李东垣提出补中益气的理论，使用人参、黄芪等甘温性质的药物，大补元气并提升下陷之气，这是利用气分药物治疗气虚不足的方法。思虑过度及房事不节，会内伤真阴，使用四物汤加入黄柏、知母，滋补阴液而使虚火自降，这是利用血分药物治疗血虚不足的方法。益气、补阴，都属于内伤病证。一种是因为阳气下陷而升提它，一种是因为阴火上炎而滋阴降火，一升一降，截然不同。
平时发热，热邪在行阳的层次，由肺脏主管，所以用白虎汤来清泻气分中的火热。日晡时（下午3-5点）潮热，热邪在行阴的层次，骨皮散治疗脉象弦紧，所以将其举升，使春生之气得以上升。
治疗热证的方法有五种：一是和，二是取，三是从，四是折，五是夺。假如是轻微的热病，应当用凉性药物调和它。调和无效后，接着用“取”法，因为热势稍大，应当用寒性药物攻取它。攻取无效后，接着用“从”法，因为热势已经很盛，应当用温性药物顺从其势。意思是药物性质温和，味道随病情需要而定。或者用寒性药因热势而用（热因寒用），味道通达所治之处；或者用寒性药配合温性药使用，或者通过发汗来解除。如果仍无效，又用“折”法，因为病势极盛，应当用逆向制约的方法。制约无效后，应当用攻下夺实的方法。攻下无效后，又用“属”法，即寻求疾病的根本属性以削弱它。因为热邪深陷在骨髓中，无法排出，针药难以到达，所以寻求其所属的根本以削弱病势。求属的方法，就是同声相应、同气相求的道理。如果仍然无效，就广泛寻求其他方法来治疗。譬如孙子用兵，在山谷中，就堵塞水源；在水陆交界处，就扼守渡口；在平原旷野，就实行千里清野。堵塞水源，相当于针刺腧穴；扼守渡口，相当于在病发之前截断病势；千里清野，比如肌肉消瘦虚弱，就广泛服用大补药物以养护正气。
When heat is accompanied by exterior syndrome, it is called Exterior Heat. When heat occurs without exterior syndrome, it is called Interior Heat. Therefore, bitter substances are used to treat the Five Zang Organs (Zang organs), which belong to Yin and reside internally; pungent substances are used to treat the Six Fu Organs (Fu organs), which belong to Yang and reside externally. Thus, it is said that internal conditions are treated with purgation, while external conditions are treated with diaphoresis.
Dietary irregularities and overexertion cause internal injury to Yuan Qi (Primordial Qi). When Yuan Qi is damaged, True Yang sinks downward, generating internal deficiency heat. Therefore, Li Dongyuan proposed the theory of Bu Zhong Yi Qi Tang (Tonify the Middle and Augment the Qi Decoction), using sweet-warm herbs such as Ren Shen (Ginseng Radix) and Huang Qi (Astragali Radix) to greatly tonify Qi and lift the sinking Qi. This is the method of using Qi-tonifying herbs to address Qi insufficiency. Excessive mental labor and sexual indulgence cause internal injury to True Yin. Si Wu Tang (Four Substances Decoction) added with Huang Bo (Phellodendri Cortex) and Zhi Mu (Anemarrhenae Rhizoma) is used to nourish Yin, causing the fire to subside naturally. This is the method of using Blood-nourishing herbs to address Blood insufficiency. Tonifying Qi and Nourishing Yin both pertain to Internal Injury syndromes. One lifts due to the sinking of Yang Qi, while the other nourishes and descends due to the rising of Yin Fire. One ascends and one descends; they are completely different.
General fever, where heat resides in the layer of Yang circulation, is governed by the Lung. Therefore, Bai Hu Tang (White Tiger Decoction) is used to clear fire from Qi-level heat. Waning fever at dusk (Ri Bu), where heat resides in the layer of Yin circulation, is treated with Gu Pi San (Bone Skin Powder). For a wiry pulse, the pathogen is lifted to allow Spring Qi to ascend.
There are five methods for treating heat: 1. Harmonizing (He), 2. Taking/Attacking (Qu), 3. Following (Cong), 4. Breaking/Restraining (Zhe), 5. Depriving/Purging (Duo). If the disease is mild heat, cool herbs should be used to harmonize it. If harmonization fails, proceed to "Taking," because the heat intensity is slightly greater, so cold herbs should be used to attack it. If attacking fails, proceed to "Following," because the heat intensity is severe, so warm herbs should be used to follow the pathogenic trend. This means the herb's nature is warm, and its flavor adapts to the treatment needs. It may involve using cold herbs in hot conditions (treating heat with cold, administered hot), or combining cold herbs with warm ones, or resolving via sweating. If this fails, proceed to "Breaking," because the pathological momentum is extreme, requiring counter-restriction. If restriction fails, proceed to "Depriving" via purgation. If purgation fails, proceed to "Belonging" (Shu), seeking the root affiliation to weaken the disease. Since heat has sunk deeply into the marrow and cannot exit, beyond the reach of acupuncture and herbs, one seeks its root affiliation to diminish it. The method of seeking affiliation follows the principle of "like responds to like, same qi attracts same qi." If still ineffective, widely seek other methods for treatment. As Sun Tzu used in warfare: in valleys, block the springs; at water-land junctions, guard the crossings; in open plains, clear the fields for a thousand li. Blocking springs corresponds to needling Shu points; guarding crossings corresponds to intercepting the disease before its onset; clearing fields for a thousand li corresponds to cases of emaciation and weakness, where one should broadly administer major tonic herbs to nourish Righteous Qi.