东垣一部《脾胃论》，俱以补中益气汤为主，无非培人后天元气之本。顾元气为生身之精气，而实祖
于胃。故胃气有谷气、荣气、卫气、宗气、阳气之别名，要皆此元气之异称，而此气即《内经》所谓“少
火生气”之气也。“少火生气”，即为真阳之气，乃生人立命之根。此火寄于肾、肝，名为相火。相火
者，因君火不主令，而代君以行，故曰∶“相火以位”。则此火本非邪火，而何得云元气之贼？元气在两肾命门
之中，随三焦相火以温分肉而充皮肤，蒸糟粕而化精微。是元气即相火之所化，而非贼元气之物。其贼元
气者，乃壮火而非相火也。若谓相火为下焦包络之火，即指为元气之贼，而曰火与元气不两立，一胜则
一负，则生元气者，更有何火耶？
《内经》论火，止有君火、相火、少火、壮火、五志之火之名，而并无有以阴火名者。其以阴火名者，
自东垣始。东垣谓心火者，阴火也，起于下焦，其系上系于心。夫心在膻中气海之中，为足厥阴包络之经，
所谓阳中之太阳也，而何得以阴火名之？既指心火为阴火，心本在上焦，而何以云起于下焦？起于下焦，
则不当指为心火矣！且土者，脾胃也。火为土之母，补土必先补火。上蒸丹田以腐熟水谷者，此心火也，即
此阴火也。岂可谓阴火来乘土位，以伤脾胃生发之气乎？火乘土以伤脾土生发之气者，必阳邪之火，而非
心君之阴火也。少阴心火，正补太阴脾土，此虚则补母之义，但不可大旺。夫火旺则土反燥，又当壮水以制之。
李东垣所著的《脾胃论》，全书以补中益气汤为主要方剂，其目的无非是培补人体后天元气的根本。元气作为构成生命的精气，实际上根源于胃。因此，胃气拥有谷气、荣气（营气）、卫气、宗气、阳气等别名，这些名称本质上都是对元气的不同称呼，而这种气正是《内经》中所说的“少火生气”的气。“少火生气”，指的是真阳之气，它是人类生存和立命的根基。这种火寄居于肾和肝，被称为相火（寄居肝肾的生理之火）。相火的作用是因为君火（心火）不直接主事，而代替君火行使职能，所以说：“相火以位”。既然这火原本不是邪火，怎么能说是元气的贼寇呢？元气位于两肾命门之中，随着三焦的相火一起温煦肌肉、充实皮肤，蒸化糟粕并转化为精微物质。由此可见，元气正是由相火所化生，而不是损害元气的东西。真正损害元气的，是壮火（亢盛的病理之火），而不是相火。如果说相火是下焦包络之火，并将其指认为元气的贼寇，声称“火与元气不两立，一胜则一负”，那么生成元气的那股力量又是什么火呢？
《内经》在论述火时，只有君火、相火、少火、壮火、五志之火（情志化火）的名称，并没有“阴火”这一说法。“阴火”这一概念，是从李东垣开始的。李东垣认为心火就是阴火，它起源于下焦，其经络上连于心。然而，心位于膻中气海之中，属于足厥阴心包经，被称为“阳中之太阳”，怎么能用“阴火”来命名它呢？既然将心火称为阴火，而心本位于上焦，为什么又说它起源于下焦？如果起源于下焦，就不应当将其指认为心火了！况且，“土”指的是脾胃。火是土的母行，补土必须先补火。向上蒸腾丹田以腐熟水谷的，正是心火，也就是所谓的阴火。怎么可以说阴火来乘袭土位，从而损伤脾胃的生发之气呢？能够乘袭脾土从而损伤脾土生发之气的，必定是阳邪之火，而不是心君的阴火。少阴心火，本来是用来补益太阴脾土的，这符合“虚则补其母”的原则，只是不可过于旺盛。如果火太旺，土反而会变得干燥，此时应当通过壮水（滋补肾阴）来制约它。
Li Dongyuan's *Pi Wei Lun* (Treatise on the Spleen and Stomach) primarily utilizes Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction), with the aim of nourishing the root of the acquired primordial Qi (acquired vital energy). Primordial Qi, as the essence and Qi constituting life, is fundamentally rooted in the Stomach. Therefore, Stomach Qi has alternative names such as Guqi (Grain Qi), Yingqi (Nutritive Qi), Weiqi (Defensive Qi), Zongqi (Gathering Qi), and Yangqi (Yang Qi); these are essentially different appellations for this same primordial Qi, which corresponds to the "Shao Huo Sheng Qi" (Lesser Fire generates Qi) mentioned in the *Neijing* (Inner Canon). "Shao Huo" refers to True Yang Qi, the root of human life and existence. This fire resides in the Kidneys and Liver and is called Xiang Huo (Ministerial Fire). Ministerial Fire acts on behalf of Jun Huo (Monarch Fire/Heart Fire) when the Monarch does not directly exercise its function, hence it is said: "Ministerial Fire operates according to its position." Since this fire is inherently not pathogenic fire, how can it be termed a thief of primordial Qi? Primordial Qi resides within the Mingmen (Gate of Life) between the two Kidneys, circulating with the Sanjiao's Ministerial Fire to warm the muscles, fill the skin, steam waste products, and transform them into essential nutrients. Thus, primordial Qi is transformed by Ministerial Fire, rather than being harmed by it. What actually harms primordial Qi is Zhuang Huo (Exuberant Fire), not Ministerial Fire. If one argues that Ministerial Fire is the fire of the Lower Jiao Pericardium and labels it a thief of primordial Qi, claiming that "Fire and Primordial Qi cannot coexist; as one wins, the other loses," then what fire is responsible for generating primordial Qi?
The *Neijing* discusses only Jun Huo (Monarch Fire), Xiang Huo (Ministerial Fire), Shao Huo (Lesser Fire), Zhuang Huo (Exuberant Fire), and Wuzhi Zhi Huo (Fire from Five Emotions), without mentioning "Yin Huo" (Yin Fire). The concept of "Yin Huo" originated with Li Dongyuan. Li Dongyuan stated that Heart Fire is Yin Fire, originating from the Lower Jiao and connecting upwards to the Heart. However, the Heart is located in the Danzhong (Chest Center) and Qi Hai (Sea of Qi), belonging to the Foot Jueyin Pericardium Meridian, and is described as "Sun among Yangs." How can it be named Yin Fire? If Heart Fire is designated as Yin Fire, yet the Heart is originally in the Upper Jiao, why is it said to originate from the Lower Jiao? If it originates from the Lower Jiao, it should not be identified as Heart Fire! Furthermore, "Earth" refers to the Spleen and Stomach. Fire is the mother of Earth; to tonify Earth, one must first tonify Fire. The fire that steams upward to the Dantian to ripen food and drink is Heart Fire, which is also referred to as Yin Fire. How can it be claimed that Yin Fire attacks the Earth position, thereby damaging the generating Qi of the Spleen and Stomach? The fire that attacks Earth and damages the Spleen's generating Qi must be Yang Pathogenic Fire, not the Yin Fire of the Heart Monarch. Shaoyin Heart Fire naturally tonifies Taiyin Spleen Earth, adhering to the principle of "tonifying the mother when deficient," provided it does not become excessively exuberant. If Fire becomes too strong, Earth will become dry; in such cases, one should strengthen Water (nourish Kidney Yin) to control it.