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1. Since the *Ling Shu* (Spiritual Pivot), *Su Wen* (Basic Questions), and *Nan Jing* (Classic of Difficult Issues), Zhang Zhongjing is primarily recommended in the medical way, as he is the ancestor of prescription formulation. However, Zhang Zhongjing discussed Shanghan (Cold Damage) but did not fully expound on the principles of Wreheat diseases (Warm Heat Diseases) and Wen Yi (Warm Epidemics). Liu Hejian (Liu Wansu) discussed Wreheat diseases and Wen Yi, but was incomplete regarding Neishang (Internal Injury). Li Dongyuan detailed the discussion on Neishang, publishing insightful treatises such as those on Buzhong Yiqi Tang (Tonify the Middle and Boost Qi Decoction) and Zhizhu Wan (Immature Bitter Orange Pill), with profound knowledge spanning millennia, yet there were still omissions regarding Yin-deficiency type Neishang. Zhu Danxi expanded upon this, proposing the theory that "Yang is often in excess, while Yin is often insufficient," to supplement what previous sages had missed, thereby making the medical way comprehensive. What more could be said? It is just that the works of these four masters, when combined, reveal their completeness; when separated, they reveal their partiality. This collection integrates the strengths of all four schools, harmonizing their subtle meanings so that each method may be suitable for clinical application, thus avoiding bias.

2. The distinction between Deficient Fire (Xu Huo) and Excess Fire (Shi Huo) is as vast as heaven and earth. Deficient Fire can be treated with tonification, while Excess Fire can be treated with purgation/draining. If mismanaged, disaster can occur as quickly as turning a palm. Here, fire generated internally is termed Zihuo (Offspring Fire), and fire arriving from externally is termed Zeihuo (Thief Fire). By distinguishing deficiency and excess to determine whether to tonify or drain, seemingly obscure principles of millennia become suddenly clear. In the process of prescribing medication according to symptoms, there is a sense of clarity and precision akin to drawing in sand or imprinting in clay.

3. All diseases essentially fall under the categories of Cold, Heat, Deficiency, Excess, Exterior, Interior, Yin, and Yang. Here, specific treatises are written to differentiate and discuss them. Summarized, they are within grasp; extrapolated, they can address infinite variations. Students should devote themselves to studying these.

4. In medical treatment, there are originally Eight Methods (Han, Tu, Xia, He, Wen, Qing, Xiao, Bu - Sweating, Vomiting, Purging, Harmonizing, Warming, Clearing, Reducing, Tonifying). However, some formula books mention five methods, others six. Contemporary physicians often adhere to biased views, using only one or two methods, considering themselves correct. This leads to treatments that do not follow proper protocols, causing mild illnesses to become severe, and severe illnesses to become critical, eventually resulting in having no effective methods left, which is deeply regrettable. Therefore, I have composed "The Eight Methods of the Medical Gate," discussing them repeatedly and in detail, so that practitioners may immerse themselves in these eight methods, enabling them to rescue the perilous and stabilize the collapsing, hopefully possessing life-saving techniques.

5. The category of Shanghan (Cold Damage) was traditionally said to comprise 397 methods and 113 prescriptions, yet still could not exhaust its variations. Thus, some claimed Zhang Zhongjing's *Treatise on Cold Damage* (*Shanghan Lun*) was not a complete work. Yet, I summarize it with merely four characters. Is this not too simple? One must not fail to realize that Shanghan involves only four aspects: Exterior, Interior, Cold, and Heat. From these four characters, eight scenarios are derived (Exterior Cold, Interior Cold, Exterior Heat, Interior Heat, Exterior and Interior both Heat, Exterior and Interior both Cold, Exterior Cold with Interior Heat, Exterior Heat with Interior Cold). Mastering these, not only can the 397 methods and 113 prescriptions be obtained effortlessly, but even thousands of changes are encompassed within them. Having studied Zhang Zhongjing's works for over ten years with some insights, I have composed the "Four-Character Treatise on Shanghan" as a bridge for future learners. Analysis is clear, principles are prominent, debates are detailed, and there is no confusion. Those treating Shanghan who take this as a model can gradually ascend to the hall and enter the inner chamber of Zhang Zhongjing's mastery.

6. The distinction between Cold and Heat in Zhongfeng (Wind Stroke) actually shifts according to the patient's Zang-Fu organs. Once this is penetrated/understood, then cooling or warming agents can be appropriately applied, resolving doubts from ancient and modern times.

7. Wind, Cold, Summer-Heat, Dampness, Dryness, and Fire constitute the Six Qi (Six Climate Factors) of Heaven. When these six qi mix and interact, they cause disease, requiring careful differentiation. If generally labeled as Shanghan and treated with dispersing agents, the harm is significant. Caution is essential at the outset.

8. Miscellaneous diseases differ in terms of Internal Injury (Neishang) and External Contraction (Waigan). Differentiating from this point prevents confusion in treatment methods and leads to rapid efficacy.

9. Women's diseases are more numerous than men's due to menstruation, pregnancy, and childbirth. Furthermore, their temperaments tend toward depression, making them prone to illness; thus, treatment methods require adaptation. These are detailed below. Diseases common to both sexes are not recorded here; only the differences are recorded. This is not an omission.