凡看人之病，兼视其形色，后与脉病相参，诚识于始，以决其终，百无一失矣。何
以知之？阴病见阳色，腮颧红显，阳病见阴色，指甲呈青，此二者俱死。又身热脉细唇
吻反青，目珠直视者死。面如涂脂，色若土黄，油腻黑气涂抹者死。唇舌干焦，鼻生烟
煤，眼神透露者死。形容憔悴，精神昏短，身形缩小者死。喘粗气短，鼻 睛露，语言谵
妄者死。循衣摸床，遗尿失禁，撮空者死。头低项软，眼视无神，吸吸短气者死。皮破无
血，肉绽烂斑，麻木不知痛痒者死。齿黄色如煮豆，唇白皮理无纹，耳黑枯焦不听，人
中缩而坦平，口张气出无回闭，鼻煽相随呼吸行，汗出如珠不散，痰若胶而坚凝，口血
红如肺色，指甲弯而带青，神昏神浮，神乱神离，缁衣生满面，黑气惨天庭，逢之都没
命。法在此中评。
三因者，内因、外因、不内外因。此说
从于先古，其词意尚有发而未尽者。内因起于七情蕴结于内，又兼浓味膏粱，熏蒸脏腑，
房欲劳伤，亏损元气，乃五脏受之，其病由此而发者多，在富贵肥胖者十有八九。其见
症形多坚硬，根蒂深固，二便不调，饮食少进，外软内坚，平陷无脓，表实里虚，毒多
难出，此即内伤之症也，故曰内因。外因者，皆起于六淫体虚之人，夏秋露卧。当风取凉，
坐眠湿地，以致风寒湿气袭于经络，又有房事后得之，其寒毒乘虚深入骨髓，与气血相
凝者尤重，或外感风邪，发散未尽，遂成肿痛。此肌肉血脉筋骨受之，其病由此外来者，
发之多在不善调摄。跌扑劳碌人十有八九，症多寒热交作，筋骨疼痛，步履艰辛，湿痰流
毒，以及诸风瘫痪，口眼歪斜，半身不遂，风湿风温，天行时毒等症，此即疾病之外感也，
故曰外因。又有不内外因，内无七情干内，外无六淫伤外，何由来也，其病得于饥饱劳役，
喜怒不常，饮食者冷热不调，动作者勤劳不惜，以致脏腑不和，荣卫不顺，脾胃受伤，经
络凝滞，故为疾者，外无六经形症，内无便溺阻隔，其病多生于肌肤之间，似瘰 痰注
气痞瘿瘤之属，治法不必发表攻里，只当养气血，调经脉，健脾和中，行痰开郁治之，法为最善。
凡是诊察病人的疾病，必须同时观察其面色和形体，然后再与脉象、病症相互参照，如果在开始时就能真正认识清楚，从而判断预后结局，那么一百次诊断中几乎不会有一次失误。
为什么能这样知道呢？阴证病人出现阳证的面色，如腮部颧骨处红赤显露；阳证病人出现阴证的面色，如指甲呈现青色，这两种情况都属于死证。
另外，身体发热但脉象细弱，嘴唇和口角反而发青，眼睛直视不动的，属于死证。
面色像涂了脂粉一样异常红润，或者颜色像土黄色，面部有油腻的黑气涂抹状的，属于死证。
嘴唇和舌头干燥焦裂，鼻孔里生出像烟煤一样的黑垢，眼神外露无神的，属于死证。
呼吸喘促粗重，气息短浅，鼻孔翕动（鼻翼扇动），眼睛外露，言语错乱胡说的，属于死证。
手不自觉地循摸衣被或床沿，大小便失禁，手指在空中虚抓（撮空理线）的，属于死证。
头低垂颈部软弱无力，眼神涣散无神，吸气短促困难的，属于死证。
皮肤破损但没有血液流出，肌肉绽开腐烂成斑块，麻木不知痛痒的，属于死证。
牙齿发黄像煮熟的豆子，嘴唇苍白且纹理消失，耳朵黑色干枯焦躁且听不见声音，人中穴部位缩短而平坦，嘴巴张开气息呼出后无法收回闭合，鼻翼煽动随着呼吸运动，出汗像珍珠一样圆润不散，痰液像胶一样坚硬凝结，口中吐出的血红色如同肺脏的颜色，指甲弯曲且带有青色，神志昏迷或浮越，神志混乱或离散，脸上布满黑气，天庭部位惨现黑气，遇到这些征象的人都会丧命。诊疗法则就包含在这些判断之中。
三因，指的是内因、外因、不内外因。这种说法源自古代先贤，但其词意还有发挥未尽的地方。
内因是由于七情（喜、怒、忧、思、悲、恐、惊）郁结于体内，又加上食用浓烈滋味和肥甘厚味，熏蒸脏腑，以及房事过度导致劳伤，亏损元气，从而由五脏受邪引发，由此产生的疾病很多，在富贵且肥胖的人群中十有八九会出现。
这类病症的表现形态多坚硬，根基深固，二便不调，饮食减少，外表看似柔软内部却坚硬，平塌凹陷没有脓液，表实里虚，毒邪难以排出，这就是内伤类的病症，所以称为内因。
外因，都是起因于六淫（风、寒、暑、湿、燥、火）侵袭体质虚弱之人，比如夏秋季节露天睡觉，对着风取凉，坐在潮湿的地方睡觉，导致风寒湿气侵袭经络；又有在房事后感受外邪的，寒毒乘虚深入骨髓，与气血相凝滞的情况尤为严重；或者是外感风邪，发散治疗不彻底，遂形成肿痛。这类病症发生在肌肉、血脉、筋骨，是由外部因素引起的疾病，大多因为调摄不当所致，在跌打损伤或劳累奔波的人群中十有八九会出现。症状多为寒热交替发作，筋骨疼痛，行走艰难，湿痰流注毒邪，以及各种风症瘫痪、口眼歪斜、半身不遂、风湿、风温、天行时毒等病症，这就是疾病的外感类，所以称为外因。
还有不内外因，内部没有七情干扰内脏，外部没有六淫伤害体表，病从何而来呢？这是因为饥饱失常、劳役过度，喜怒无常，饮食冷热不调，劳作勤劳不顾惜身体，导致脏腑不和，营卫不顺，脾胃受伤，经络凝滞，因此产生的疾病。这类疾病外部没有六经（太阳、阳明、少阳、太阴、少阴、厥阴）的形症表现，内部没有大小便的阻隔，病多生于肌肤之间，类似瘰疬、痰核、气痞、瘿瘤之类的病症。治疗方法不必使用发表攻里的方法，只应当调养气血，调理经脉，健脾和中，化痰开郁进行治疗，这种方法最为妥善。
Whenever examining a patient's disease, one must simultaneously observe their complexion and physical form, and then cross-reference these with the pulse and symptoms. If one can truly understand the condition at the beginning, thereby determining the prognosis, there will be almost no errors in a hundred diagnoses.
How is this known? When a Yin syndrome (syndrome characterized by deficiency, cold, or interior pathology) presents with Yang-colored features, such as redness appearing on the cheeks and zygomatic arches; or when a Yang syndrome presents with Yin-colored features, such as cyanosis of the fingernails, both are considered fatal signs.
Additionally, if the body is hot but the pulse is fine/thin, the lips and corners of the mouth turn blue/cyan, and the eyes are fixed/staring straight ahead, this is a sign of death.
If the face looks as if coated with rouge, or has a color resembling yellow earth, with an oily black aura smearing the face, this is a sign of death.
If the lips and tongue are dry and scorched, black soot-like deposits appear in the nostrils, and the spirit/eyes reveal themselves without depth/focus, this is a sign of death.
If the appearance is emaciated and haggard, the spirit is confused and short, and the body shape shrinks, this is a sign of death.
If breathing is panting and coarse, qi is short, the nostrils flare (alae nasi move), the eyes protrude, and speech is delirious/wild, this is a sign of death.
If the patient unconsciously grasps at clothes or bed rails, loses control of urination and defecation, and makes empty grasping movements in the air (picking at empty space), this is a sign of death.
If the head hangs low and the neck is soft/flaccid, the eyes look without spirit, and inhalation is shallow and short, this is a sign of death.
If the skin is broken but no blood flows, the flesh splits and rots into patches, and there is numbness without sensation of pain or itch, this is a sign of death.
If the teeth are yellow like boiled beans, the lips are white with no texture/lines, the ears are black, dry, scorched, and deaf to hearing, the philtrum (area between nose and upper lip) is shortened and flat, the mouth is open with exhaled breath unable to close/recirculate, the nostrils flare accompanying respiration, sweat beads up like pearls and does not disperse, phlegm is sticky and hardens like glue, the blood spat from the mouth is red like the color of the lung, the fingernails are curved and tinged with cyan, the spirit is confused or floating, the spirit is chaotic or detached, black qi covers the entire face, and a grim black aura appears on the forehead (Tian Ting); encountering any of these means loss of life. The diagnostic methods are evaluated within these descriptions.
The "Three Causes" refer to Internal Causes, External Causes, and Non-Internal/External Causes. This theory originates from ancient times, though its meaning has not been fully elaborated.
Internal Causes arise from the accumulation of the Seven Emotions (Joy, Anger, Worry, Thought, Sorrow, Fear, Fright) inside the body, combined with the consumption of rich flavors and fatty/sweet foods, which steam and damage the Zang-Fu organs. It also includes sexual excess causing labor injury and depleting Yuan Qi (Original Qi). These affect the Five Zang Organs, and diseases arising from this source are common, occurring in nine out of ten cases among the wealthy and obese.
The manifestations of these conditions are often hard and solid, with deep roots. There is irregularity in urination and defecation, reduced food intake, a soft exterior but hard interior, flat depressions without pus, excess at the exterior but deficiency at the interior, and difficulty expelling toxins. These are internal injury syndromes, hence called Internal Causes.
External Causes all originate from the invasion of the Six Excesses (Wind, Cold, Summer-heat, Dampness, Dryness, Fire) in individuals with weak constitutions, such as sleeping outdoors in summer and autumn, cooling off in the wind, or sitting/sleeping on damp ground, leading to Wind-Cold-Dampness invading the meridians. Another scenario is contracting pathogens after sexual intercourse, where Cold-Toxin penetrates deeply into the bone marrow due to deficiency, coagulating with Qi and Blood, which is particularly severe. Or, external Wind pathogen was not fully dispersed through sweating/diffusing therapies, resulting in swelling and pain. These affect muscles, blood vessels, and bones/tendons. Diseases caused by external factors often result from poor self-care, occurring in nine out of ten cases among those suffering from falls/fractures or overwork. Symptoms often include alternating chills and fever, bone and joint pain, difficult walking, flowing toxic phlegm, various wind syndromes leading to paralysis, facial deviation, hemiplegia, Wind-Dampness, Wind-Warmth, and epidemic toxins. These are external contractive diseases, hence called External Causes.
There are also Non-Internal/External Causes. If there is no internal disturbance by the Seven Emotions and no external injury by the Six Excesses, where do the diseases come from? They arise from irregular eating and drinking, overwork and fatigue, inconsistent emotions (excessive joy or anger), improper temperature of food and drink, and excessive labor without regard for one's health. This leads to disharmony of the Zang-Fu organs, unsmooth Ying and Wei (Nutritive and Defensive) Qi, injury to the Spleen and Stomach, and stagnation of the meridians. Consequently, the disease manifests externally without the typical signs of the Six Meridians (Taiyang, Yangming, Shaoyang, Taiyin, Shaoyin, Jueyin) and internally without obstruction of urination or defecation. The disease mostly arises between the skin and muscles, resembling conditions such as scrofula (Luo Li), phlegm nodules (Tan Zhu), Qi痞 (Qi Pi), and goiter (Ying Liu). The treatment method should not involve releasing the exterior or purging the interior, but rather nourishing Qi and Blood, regulating meridians, strengthening the Spleen and harmonizing the Middle Jiao, resolving phlegm, and opening depression. This approach is considered the most excellent.