尝思一阴一阳，互为之根，天地之气化也。人禀天地之气化以生，即人身各具一小天地，其气化何独
不然。是以人之全身，阴阳互相维系，上焦之阳藏于心中血，中焦之阳涵于胃液，下焦之阳存于肾水，凡心
血、胃液、肾水皆阴也。充类言之，凡全身津液脂膏脉腺存在之处，即元阳留蓄之处。阳无阴则飞越，阴无
阳则凝滞。阳盛于阴则热，阴盛于阳则冷。由斯知阴阳偏盛则人病，阴阳平均则人安，阴阳相维则人生，阴
阳相离则人死。彼为贵阳抑阴之论者，竟谓阳一分未尽则人不死，阴一分未尽则人不仙，斯何异梦中说梦也。
然此则论未病之时，阴阳关于人身之紧要，原无轩 也。若论已病，又恒阳常有余，阴常不足（朱丹溪曾有此论）。
医者当调其阴阳，使之归于和平，或滋阴以化阳，或泻阳以保阴，其宜如此治者，又恒居十之八九。倘曰
不然，试即诸病征之。
病有内伤外感之殊，而外感实居三分之二。今先以外感言之，伤寒、温病、疫病皆外感也，而伤寒中于
阴经，宜用热药者，百中无二三也；温病则纯乎温热，已无他议；疫病虽间有寒疫，亦百中之一二也。他
如或疟，或疹，或痧证，或霍乱，亦皆热者居多，而暑 之病更无论矣。
试再以内伤言之。内伤之病，虚劳者居其半，而劳字从火，
其人大抵皆阴虚阳盛，究之亦非真阳盛，乃阴独虚致阳偏盛耳。他如或吐衄，或淋痢，或肺病、喉病、眼疾，
或黄胆，或水病、肿胀、二便不利，或嗽，或喘，或各种疮毒，以上诸证，已为内伤之大凡，而阳盛阴虚者
实为十之八九也。世之业医者，能无于临证之际，以急急保其真阴为先务乎？即其病真属阳虚，当用补
阳之药者，亦宜少佐以滋阴之品；盖上焦阴分不虚而后可受参、 ，下焦阴分不虚而后可受桂、附也。
I have pondered that Yin and Yang are mutually rooted, which is the law of Qi transformation in Heaven and Earth. Humans are born by inheriting the Qi transformation of Heaven and Earth; thus, each human body constitutes a small Heaven and Earth. Why should its Qi transformation be any different? Therefore, Yin and Yang in the whole body maintain each other: the Yang Qi of the Upper Jiao (Upper Burner) is stored in the blood of the Heart; the Yang Qi of the Middle Jiao (Middle Burner) is contained within the Stomach fluids; and the Yang Qi of the Lower Jiao (Lower Burner) resides in the Kidney water. All these—Heart blood, Stomach fluids, and Kidney water—are Yin. Extending this logic, wherever fluids, fats, vessels, and glands exist in the whole body, there the Primordial Yang (Yuan Yang, the most fundamental Yang Qi of the body) is accumulated. Without Yin, Yang will fly away and scatter; without Yang, Yin will stagnate and coagulate. When Yang prevails over Yin, heat occurs; when Yin prevails over Yang, cold occurs. From this, we know that when Yin and Yang are imbalanced, disease arises; when they are balanced, health prevails; when they mutually sustain each other, life continues; and when they separate, death ensues. Those who advocate the theory of "valuing Yang and suppressing Yin" claim that as long as even a fraction of Yang remains, one does not die, and as long as even a fraction of Yin remains, one cannot become an immortal. How is this different from dreaming within a dream? However, this discussion pertains to the state before illness, where Yin and Yang are equally crucial to the human body, with no superiority or inferiority between them. But when discussing existing illness, it is often the case that Yang is constantly in excess and Yin is constantly deficient (a view previously held by Zhu Danxi). Physicians should regulate Yin and Yang to restore harmony, either by nourishing Yin to transform Yang, or by purging Yang to preserve Yin. Such treatments account for nine out of ten cases. If one claims otherwise, let us verify this against various diseases.
Diseases differ into internal injury and external contraction, with external contractions accounting for two-thirds. Let us first discuss external contractions. Shanghan (Cold Damage), Wenbing (Warm Diseases), and epidemics all belong to external contractions. Among Shanghan cases, those attacking the Yin meridians and suitable for hot medicines are fewer than two or three in a hundred; Wenbing is purely warm-heat in nature, leaving no room for debate; although epidemics occasionally include cold epidemics, they constitute only one or two in a hundred. Other conditions such as malaria, rashes, sha syndrome (sand poisoning), and cholera are also predominantly heat-related, while diseases caused by summer-heat are even more so.
Let us further discuss internal injuries. Among internal injuries, consumptive diseases (Xu Lao) account for half. The character for "consumption" (Lao) contains the radical for fire; thus, such patients generally suffer from Yin deficiency and Yang excess. Ultimately, this is not true Yang excess, but rather Yang appearing excessive due to isolated Yin deficiency. Other conditions such as hematemesis (vomiting blood), epistaxis (nosebleed), stranguria (dysuria), dysentery, lung diseases, throat diseases, eye disorders, jaundice, edema, swelling, difficulty in urination and defecation, cough, asthma, and various toxic sores represent the general scope of internal injuries, among which Yin deficiency and Yang excess indeed account for nine out of ten. Do physicians in the world not consider urgently preserving True Yin as their primary task during clinical practice? Even if the disease truly belongs to Yang deficiency and requires Yang-tonifying medicines, it is still appropriate to add a small amount of Yin-nourishing herbs; because only when the Yin aspect of the Upper Jiao is not deficient can it tolerate the tonification of Ginseng Radix et Rhizoma (Renshen) and Astragali Radix (Huangqi); and only when the Yin aspect of the Lower Jiao is not deficient can it tolerate the warming properties of Cinnamomi Ramulus (Guizhi) and Aconiti Lateralis Radix Praeparata (Fuzi).