凡看人病，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
颧红献；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，歙歙短气者死。皮破无血，肉绽烂斑，麻木不知痛痒
者死。齿黄色如煮豆，唇白反理无纹，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，白血红如肺色，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。内因者，皆起于七情蕴结于内
，又兼浓味膏粱熏蒸脏腑，房欲劳伤亏损元气，乃五脏受之，其病由此内发者，但发之多在富贵人及肥胖者十
有八、九。其见症，疮多坚硬，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
，得此者即病症之内伤也，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，浇薄劳碌人，十有八、九。见症多寒热
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，得
此者即疾病之外感也，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？其病得之于饥
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，其病多生于膜外肉里肌肤之间，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。此
是三因理之尽矣。
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、病症相互参验，如果在开始时就能真正认识清楚，从而判断预后，那么一百次诊断中也不会有失误。怎么知道这些呢？阴证病人如果见到阳色的表现，如腮部和颧骨部位红赤鲜明；或者阳证病人如果见到阴色的表现，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，是死证。面色像涂了脂粉一样红润，色泽像泥土黄色，或者有油腻的黑气涂抹在脸上的，是死证。嘴唇和舌头干燥焦枯，鼻孔生出像烟煤一样的黑垢，眼神外露无神的，是死证。形体消瘦憔悴，精神昏沉短促，身形缩小的，是死证。呼吸喘促粗重、气短，鼻孔张开、眼球突出，言语错乱胡说的，是死证。手不自觉地抓摸衣被和床沿，大小便失禁，手在空中虚抓（撮空理线）的，是死证。头低垂、颈项软弱无力，眼神涣散无神，气息短促微弱的，是死证。皮肤破损但没有血液流出，肌肉绽开溃烂成斑，麻木不知痛痒的，是死证。牙齿颜色黄得像煮过的豆子，嘴唇苍白且纹理断裂，耳朵黑色干枯焦躁且听力丧失，鼻下人中穴缩短而平坦，嘴巴张开气息呼出后无法闭合收回，鼻翼随呼吸煽动，出汗像珍珠一样凝聚不散，痰液像胶一样坚硬凝结，咳出的血白色或红色如同肺脏的颜色，指甲弯曲且带有青色，神志昏迷、浮越、混乱、离散，面色黑气布满满面，天庭部位出现惨烈的黑气，遇到这些征象的人都会丧命，判断方法就在这里面评述。
三因，指的是内因、外因和不内外因，这种说法沿袭自古代，但其词意还有发挥未尽的地方。内因，都是起源于七情（喜、怒、忧、思、悲、恐、惊）郁结于体内，又加上浓味厚腻的食物熏蒸脏腑，房事过度劳伤导致元气亏损，这是五脏受病，疾病由此从内部发出的，发病大多在富贵人和肥胖者身上占十分之八九。其见到的症状，疮疡多坚硬，根蒂深固，大小便不调，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，得到这种病的就是病症中的内伤，所以叫内因。外因，都是起源于六淫（风、寒、暑、湿、燥、火）侵袭体虚之人，夏天秋天露天睡觉，对着风取凉，坐在潮湿的地方睡觉，导致风寒湿气侵袭经络；又有房事后感受此邪，寒毒乘虚深入骨髓，与气血相凝滞的尤其严重；或者外感风邪，发散不彻底，遂成肿痛。这是肌肉、血脉、筋骨受病，疾病由此从外部侵入的，发病大多在不善于调养、生活浇薄劳碌的人身上占十分之八九。见到的症状多是寒热交替发作，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，得到这种病的就是疾病的外感，所以叫外因。又有不内外因，内部没有七情干扰内脏，外部没有六淫伤害体表，病是从哪里来的呢？这种病得之于饥饱失常、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。所以患这种病的人，外部没有六经的症状表现，内部没有大小便的阻隔，其病多生于膜外、肉里、肌肤之间，类似瘰疬、痰注、气痞、瘿瘤之类的病症，治疗方法不必用发表攻里的方法，只应当补养气血，调理经脉，健脾和中、行痰开郁来治疗，这种方法最为妥善。这就是三因理论的完备之处了。
When examining a patient's illness, one must simultaneously observe their facial complexion and physical form, then correlate these with the pulse and symptoms. If this is truly understood at the beginning, the prognosis can be determined accurately, resulting in no errors in a hundred cases. How is this known? If a Yin syndrome presents with Yang-colored signs, such as bright redness on the cheeks and zygomatic arches; or if a Yang syndrome presents with Yin-colored signs, such as cyanosis of the fingernails, both of these indicate death. Additionally, body heat with a fine pulse, lips and corners of the mouth turning blue, and fixed staring eyes indicate death. A face looking like it is coated with rouge, color resembling earthy yellow, or oily black qi smeared on the face indicates death. Dry and scorched lips and tongue, nose producing soot-like black deposits, and exposed spirit in the eyes indicate death. Emaciated appearance, dull and short-spirited demeanor, and shrunken body shape indicate death. Rapid and coarse breathing with shortness of breath, flaring nostrils, protruding eyes, and delirious speech indicate death. Grasping at clothes and bedrails, involuntary urination and defecation, and grasping at empty air (cuo kong) indicate death. Head drooping, neck weakness, spiritless eyes, and shallow, short breathing indicate death. Broken skin without bleeding, ruptured and ulcerated flesh with spots, and numbness without sensation of pain or itch indicate death. Teeth yellow like boiled beans, white lips with cracked textures, black and dry ears with hearing loss, shortened and flat philtrum, open mouth with exhaled air unable to close back, nasal flaring accompanying respiration, sweat beads that do not disperse, phlegm hardening like glue, blood that is white or red like lung tissue, curved nails with cyanosis, confused, floating, chaotic, or scattered spirit, black qi covering the face, and tragic black qi on the forehead—all these signs lead to death. The method for evaluating these lies herein.
The "Three Causes" refer to Internal Causes, External Causes, and Non-Internal/External Causes. This theory follows ancient precedents, though its meaning has not been fully expounded. Internal Causes originate from the stagnation of the Seven Emotions (Joy, Anger, Worry, Thought, Sorrow, Fear, Fright) within, combined with the steaming of the Zang-Fu organs by rich and greasy foods, and the depletion of Yuan Qi due to excessive sexual activity and fatigue. These affect the Five Zang Organs, and diseases arising internally are most common among wealthy individuals and the obese, accounting for eight or nine out of ten. The presenting symptoms include ulcers that are hard with deep roots, irregular bowel movements and urination, poor appetite, soft exterior but hard interior, flat depression without pus, excess in the Exterior and deficiency in the Interior, and difficulty in expelling toxins. Such cases constitute internal injury within the disease pathology, hence termed "Internal Cause."
External Causes arise when the Six Excesses (Wind, Cold, Summer-heat, Dampness, Dryness, Fire) invade those with deficient constitutions. Examples include sleeping outdoors in summer or autumn, cooling off in drafts, or sitting/sleeping on damp ground, leading to Wind-Cold-Dampness invading the meridians. It may also occur 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 invasion that is not fully dispersed leads to swelling and pain. These affect muscles, blood vessels, and sinews/bones. Diseases arising externally are most common among those who fail to regulate their lifestyle, living frugally and laboring heavily, accounting for eight or nine out of ten. Presenting symptoms often include alternating chills and fever, bone and joint pain, difficult walking, flowing toxic phlegm, various wind syndromes causing paralysis, deviation of the mouth and eye, hemiplegia, Wind-Dampness, Wind-Warmth, and epidemic toxic diseases. Such cases constitute external contraction in disease pathology, hence termed "External Cause."
There is also the Non-Internal/External Cause. If there is no internal disturbance by the Seven Emotions and no external injury by the Six Excesses, where does the disease come from? Such diseases result from irregular eating and drinking, overwork, frequent anger or joy, improper temperature of food and drink, and excessive labor without rest, leading to disharmony of the Zang-Fu organs, unsmooth Ying and Wei circulation, spleen and stomach injury, and meridian stagnation. Patients with such conditions present with no Six Channels symptoms externally and no obstruction of stool or urine internally. The disease typically arises between the fascia, muscle layers, and skin, resembling scrofula (luo li), phlegm nodules, Qi痞 (qi pi), or goiters (ying liu). Treatment 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, moving phlegm, and resolving stagnation. This is the most appropriate method. Thus, the theory of the Three Causes is fully explained.