凡治伤寒，须先辨阳证阴证。若病自三阳不能解散，而传入三阴，则寒郁为热，因成阳证。盖
其初病，必发热头痛，脉浮紧，无汗，以渐而深，乃入阴经。此邪自阳分传来，愈深则愈热，虽在
阴经，亦阳证也。其脉必沉实有力，其证必烦热炽盛，此当攻里，或消或下，随宜而用。若内不有
热，安得谓之阳证乎？若初起本无发热头痛等证，原不由阳经所传，而径入阴分者，其证或厥冷，
或呕吐，或腹痛泻利，或畏寒不渴，或脉来沉弱无力，此皆元阳元气之不足，乃为真正阴证。经曰
∶发热恶寒发于阳，无热恶寒发于阴。此以传经不传经而论阴阳也。阴阳之治，又当辨其虚实如下∶
一、治伤寒，凡阳证宜凉宜泻，阴证宜补宜温，此大法也。第以经脏言阴阳，则阴中本有阳证，
此传经之热邪也。以脉证言阴阳，则阳中最多阴证，此似阳之虚邪也。惟阴中之阳者易辨，而阳中
之阴者为难知耳。如发热狂躁，口渴心烦，喜冷，饮水无度，大便硬，小便赤，喉痛口疮，声粗气
急，脉来滑实有力者，此真阳证也。其有身虽热，而脉来微弱无力者，此虽外证似阳，实非阳证。
观陶节庵曰∶凡发热面赤烦躁，揭去衣被，唇口赤裂，言语善恶不避亲疏，虚狂假斑，脉大者，人
皆不识，认作阳证，殊不知阴证不分热与不热，须凭脉下药、至为切当。不问脉之浮沉、大小，但
指下无力，重按全无，便是阴脉，不可与凉药，服之必死，急与五积散，通解表里之寒，甚者必须
加姜附以温之。又曰∶病自阳分传入三阴者，俱是脉沉，妙在指下有力无力中
分，有力者为阳，为实为热，无力者为阴，为虚为寒，此节庵出人之见也。然以余观之，大都似阳
非阳之证，不必谓其外热、烦躁、微渴、戴阳之类，即皆为阴证也，但见其元阳不足，而气虚于中
，虽有外热，即假热耳，设用清凉消耗，则中气愈败，中气既败，则邪气愈强，其能生乎？故凡遇
此等证候，必当先其所急。人知所急在病，而不知所急在命，元气忽去，疾如绝弦，呼吸变生，
挽无及矣。治例另列后卷。
一、伤寒纲领，惟阴阳为最，此而有误，必致杀人。然有纯阳证，有纯阴证，是当定见分治也
。又有阴阳相半证，如寒之即阴胜，热之即阳胜，或今日见阴，而明日见阳者有之，今日见阳，而
明日变阴者亦有之，其在常人最多此证，盘珠胶柱，惟明哲者之能辨也。然以阴变阳者多吉，以阳
变阴者多凶，是又不可不察。
凡病患开目喜明，欲见人，多谈者属阳；闭目喜暗，不欲见人，懒言者属阴。
《论》曰∶夫阳盛阴虚，汗之则死，下之则愈；阳虚阴盛，汗之则愈，下之则死。又曰∶桂枝
下咽，阳盛则毙，承气入胃，阴盛以亡。按∶此阴阳二字，乃以寒热为言也。阳盛阴虚，言内热有
余，而外寒不甚也。夫邪必入腑，然后作热，热实于内，即阳盛也，故再用温热以汗之，则死矣。
阳虚阴盛，言寒邪有余，而蓄热未深也。夫邪中于表，必因风寒，寒束于外，即阴盛也，故妄用沉
寒以下之，则死矣。所以阳盛者用桂枝则毙，阴盛者用承气则亡。
凡治疗伤寒，必须先辨别阳证和阴证。如果病邪从三阳经不能解散，而传入三阴经，那么寒邪郁结化为热邪，从而形成阳证。大概是因为初起时，必然出现发热、头痛、脉浮紧、无汗等症状，病邪逐渐深入，才进入阴经。这是邪气从阳分传来，病位越深则热势越重，虽然病在阴经，也属于阳证。此时的脉象必定沉实有力，症状必定烦热炽盛，这种情况应当攻逐里邪，或消导或泻下，根据具体情况选用适宜的方法。如果体内没有热邪，怎么能称为阳证呢？
如果初起本来就没有发热、头痛等症状，原本不是由阳经传变而来，而是直接侵入阴分的，其症状或是四肢厥冷，或是呕吐，或是腹痛腹泻，或是畏寒口不渴，或是脉象沉弱无力，这些都是元阳元气不足的表现，这才是真正的阴证。《内经》说：“发热恶寒发于阳，无热恶寒发于阴。”这是根据是否经过传经来论述阴阳的。对于阴阳证的治疗，又应当辨别虚实，如下所述：
第一，治疗伤寒，凡是阳证宜用凉法、宜用泻法，阴证宜用补法、宜用温法，这是大原则。但如果从经络脏腑的角度谈论阴阳，那么阴经中本也有阳证，这是传经而来的热邪。如果从脉象症状的角度谈论阴阳，那么阳证中最多的其实是阴证，这是看似阳证的虚邪。只有阴中之阳比较容易辨别，而阳中之阴却难以知晓。例如出现发热、狂躁、口渴、心烦、喜冷饮、饮水无度、大便干硬、小便赤黄、咽喉疼痛、口舌生疮、声音粗重、气息急促、脉象滑实有力的，这是真正的阳证。如果有身体虽热，但脉象微弱无力的，这虽然外表症状像阳证，实际上并非阳证。
观察陶节庵（陶华）说：“凡是发热、面红、烦躁，掀开衣被，嘴唇口角赤裂，言语错乱不分亲疏，虚性狂躁、假斑疹，脉象大的，人们往往不认识，误认为是阳证，殊不知阴证不分有热与无热，必须凭脉象用药，最为恰当。不问脉象是浮是沉、是大是小，只要指下感觉无力，重按完全空虚，就是阴脉，不可给予凉药，服用后必死无疑，应立即给予五积散，通解表里的寒邪，严重的必须加入干姜、附子以温补。”他又说：“病邪从阳分传入三阴的，脉象都是沉脉，精妙之处在于指下有力还是无力中区分，有力者为阳、为实、为热，无力者为阴、为虚、为寒，这是陶节庵高明的见解。”然而依我看来，大多数看似阳证而非真阳证的病症，不必认为其外热、烦躁、微渴、戴阳等现象，就全都是阴证。只要见到元阳不足，中气虚弱，即使有外热，也是假热。如果施用清凉药物消耗正气，那么中气会更加败坏，中气既已败坏，邪气就会更加猖獗，人还能存活吗？所以凡是遇到这类证候，必须首先处理最紧急的情况。人们知道治疗的急务在于治病，却不知道更紧急的是保命，元气一旦忽然离去，病情变化快如断弦，呼吸之间发生变故，想要挽救就来不及了。具体的治例另列在后卷。
第二，伤寒的纲领，以阴阳最为重要，这里如果有误，必然导致死亡。然而有纯阳证，有纯阴证，应当明确判断分别治疗。又有阴阳各半的证候，如用寒药则表现为阴胜，用热药则表现为阳胜，或者今天见阴证，明天见阳证的情况有之；今天见阳证，明天变为阴证的情况也有之，这在常人身上最多见这种证候，如同盘珠胶柱般固定不变，只有明智的人才能辨别。然而，由阴转阳的多为吉兆，由阳转阴的多为凶险，这又是不可不察知的。
凡是病人睁眼喜欢光亮，想见人，多说话的属于阳证；闭眼喜欢黑暗，不想见人，懒于说话的属于阴证。
《伤寒论》说：“阳盛阴虚，发汗则死，攻下则愈；阳虚阴盛，发汗则愈，攻下则死。”又说：“桂枝汤服下，若阳盛则毙命；承气汤入胃，若阴盛则亡故。”按：这里的阴阳二字，是以寒热而言的。阳盛阴虚，是指内热有余，而外寒不严重。邪气必须进入腑，然后产生热邪，热邪实于内，就是阳盛，所以再用温热药发汗，就会致死。阳虚阴盛，是指寒邪有余，而蓄热未深。邪气中于体表，必然因为风寒，寒邪束于外，就是阴盛，所以妄用沉寒药攻下，就会致死。因此，阳盛者用桂枝汤则会毙命，阴盛者用承气汤则会死亡。
In the treatment of Shanghan (Cold Damage), one must first differentiate between Yang syndromes and Yin syndromes. If pathogenic factors fail to resolve in the Three-Yang meridians and transmit into the Three-Yin meridians, cold stagnation transforms into heat, thereby forming a Yang syndrome. Generally, at the onset, symptoms such as fever (Fever), headache (Headache), floating and tight pulse (Floating-Tight Pulse), and anhidrosis (Absence of sweating) are present. As the pathogen gradually penetrates deeper, it enters the Yin meridians. Since the pathogen originates from the Yang aspect, the deeper it goes, the more intense the heat becomes; thus, even when located in the Yin meridians, it is still classified as a Yang syndrome. The pulse will necessarily be deep, solid, and forceful (Deep-Solid-Forceful Pulse), and the symptoms will feature intense irritability and high fever (Irritability and High Fever). In such cases, one should attack the interior, employing either resolution or purgation methods as appropriate. How can it be called a Yang syndrome if there is no internal heat?
If, however, the onset lacks symptoms such as fever and headache, does not originate from transmission via Yang meridians, but directly invades the Yin aspect, the symptoms may include cold extremities (Cold Extremities), vomiting (Vomiting), abdominal pain with diarrhea (Abdominal Pain and Diarrhea), aversion to cold without thirst (Aversion to Cold and No Thirst), or a deep, weak, and powerless pulse (Deep-Weak-Powerless Pulse). These all indicate insufficiency of Primordial Yang and Yuan Qi (Primordial Energy), constituting true Yin syndromes. The Classic states: "Fever with aversion to cold arises from Yang; absence of fever with aversion to cold arises from Yin." This differentiates Yin and Yang based on whether transmission has occurred. Regarding the treatment of Yin and Yang syndromes, one must further distinguish deficiency and excess as follows:
First, in treating Shanghan, Yang syndromes generally require cooling and purging methods, while Yin syndromes require tonifying and warming methods; this is the general principle. However, discussing Yin and Yang in terms of meridians and zang-fu organs, Yin meridians can contain Yang syndromes, which are heat pathogens transmitted through meridians. Discussing Yin and Yang in terms of pulses and symptoms, Yang syndromes often contain Yin elements, which are deficient pathogens resembling Yang. It is easier to identify Yang within Yin than to discern Yin within Yang. For instance, symptoms such as fever, mania/restlessness (Mania and Restlessness), thirst, vexation (Vexation), preference for cold drinks, excessive water intake, hard stools, red urine, sore throat, mouth ulcers, coarse voice, rapid breathing, and a slippery, solid, and forceful pulse constitute true Yang syndromes. Conversely, if the body is hot but the pulse is weak and powerless, although the external signs resemble Yang, it is actually not a Yang syndrome.
Observing Tao Jie'an (Tao Hua): "Whenever there is fever, flushed face, restlessness, removal of clothes and blankets, cracked red lips and mouth, confused speech disregarding kinship, false mania, and false macules, along with a large pulse, people often fail to recognize them, mistaking them for Yang syndromes. They do not realize that Yin syndromes, regardless of presence or absence of heat, must be treated based on the pulse, which is most appropriate. Regardless of whether the pulse is floating or deep, large or small, if it feels powerless under the fingers and completely empty upon heavy pressure, it is a Yin pulse. Do not administer cooling medicines; doing so will surely cause death. Immediately administer Wuji San (Five Accumulations Powder) to resolve exterior and interior cold. In severe cases, add Shengjiang (Dried Ginger) and Fuzi (Prepared Aconite Root) to warm." He also stated: "When disease transmits from Yang to the Three-Yin, the pulse is always deep. The subtlety lies in distinguishing strength versus weakness under the fingers: strong indicates Yang, excess, and heat; weak indicates Yin, deficiency, and cold. This is Tao Jie'an's profound insight." However, in my view, most conditions that resemble Yang but are not true Yang—such as external heat, restlessness, slight thirst, and floating Yang (Floating Yang)—are not all Yin syndromes. One must observe if Primordial Yang is insufficient and Qi is deficient in the center. Even if there is external heat, it is false heat. If cooling and consuming medicines are used, the Middle Qi (Middle Qi) will deteriorate further. Once Middle Qi fails, pathogenic factors become stronger, and survival is unlikely. Therefore, when encountering such conditions, one must address the most urgent priority. People know the urgency lies in treating the disease, but fail to realize the greater urgency lies in preserving life. If Yuan Qi suddenly departs, the change is swift as a snapping string; breath changes occur, and rescue becomes impossible. Specific treatment examples are listed in the subsequent volume.
Second, the outline of Shanghan prioritizes Yin and Yang above all else. Errors here inevitably lead to death. There are pure Yang syndromes and pure Yin syndromes, which require definitive differentiation and separate treatment. There are also mixed Yin-Yang syndromes, where cold therapy reveals Yin dominance, or heat therapy reveals Yang dominance. Sometimes, a Yin syndrome appears today and a Yang syndrome tomorrow, or vice versa. Such cases are most common among ordinary people and are rigid like fixed beads on a string; only the wise can distinguish them. However, transformation from Yin to Yang is mostly auspicious, while transformation from Yang to Yin is mostly ominous, which requires careful observation.
Patients who keep their eyes open, prefer brightness, desire to see people, and speak much belong to Yang syndromes. Patients who keep their eyes closed, prefer darkness, do not wish to see people, and speak little belong to Yin syndromes.
The Treatise states: "When Yang is excess and Yin is deficiency, sweating causes death, purging leads to recovery. When Yang is deficiency and Yin is excess, sweating leads to recovery, purging causes death." It also states: "If Guizhi Tang (Cinnamon Twig Decoction) is swallowed, Yang excess leads to demise; if Chengqi Tang (Stomach-Clearing Decoction) enters the stomach, Yin excess leads to death." Note: Here, Yin and Yang refer to cold and heat. "Yang excess and Yin deficiency" means internal heat is surplus while external cold is mild. Pathogens must enter the Fu organs to generate heat; heat solidifies internally, constituting Yang excess. Thus, using warm herbs to induce sweating causes death. "Yang deficiency and Yin excess" means cold pathogens are surplus while accumulated heat is shallow. Pathogens strike the exterior due to wind-cold; cold binds externally, constituting Yin excess. Thus, recklessly using cold-purgative herbs causes death. Therefore, using Guizhi Tang in Yang excess leads to death, and using Chengqi Tang in Yin excess leads to death.