《灵枢》曰∶人气有清浊，受气者清。清者注阴，故上注于肺（手太阴），其气滑然；清者有浊，清之浊
者，下行于经，内积于海。诸阴皆清，足下走于胃（足阳明），其气涩然。浊者有清，浊之清者，上出于咽及
口。诸阳皆浊，手太阳（小肠经）独受其浊，此为阳浊独甚也（次第《阴阳清浊》篇文）。
《素问》曰∶邪气盛则实，精气夺则虚。寸脉急而尺缓者，经络皆实也。脉口热而尺寒者，络虚而经实也
（脉口，即寸口）。尺脉满，脉口寒涩者，经虚而络满也
（满，即实也）。大热病，气热脉满者，重实也（气与脉俱实也）。脉虚（经云∶脉虚者，不象阴也。然气口脉
之要会，手太阴之动也，故不象阴为脉应）、气虚（经云∶气虚者无常也。谓膻中气不定也，旧注谓寸脉动无
常者非）、尺虚者（行步 然），重虚也（ 括《通评虚实论篇》文）。
《难经》曰∶病有虚实，出者为虚，入者为实（从内之外为出，从外之内为入）。言者为虚，不言者为实
（言者病而尚能言也，不言者病而不能言也）。缓者为虚，急者为实（缓急以病势言）。脉有虚实，濡者为虚，
紧牢者为实（濡者，阴金也，按之似有，举之若无。紧者，阳木也，按之有余，举之甚数，状若洪弦，三关通
度。牢者，阴木也，寻之即无，按之却有，沉而有力，动而不移）。诊有虚实（诊，视验也，探病之通称，兼
望闻问切而言），濡者为虚，牢者为实（濡牢虽与脉相类，然此所包者广）；痒者为虚，痛者为实（气欲通则
痒，不通则痛）；外通内快，为外实内虚，内痛外快，为内实外虚（快，爽也），此为三虚、三实（凡言虚
者，谓精气夺也，实者谓邪气盛也）。（次第《四十八难》文）
《素问》又曰∶五实死，五虚死（五，五脏也）。脉盛（心实），皮热（肺实），腹胀（脾实），前后不
通（肾实），闷瞀（肝实），此为五实；脉细（心虚），皮寒（肺虚），气少（肝虚），泄利前后（肾虚），
饮食不入（脾虚），此谓五虚。然时有生者，何也？浆粥入胃，泄注止，则虚者活；身汗得，后利，则实者活
（稍次《玉机真藏论篇》文）。
《灵枢》说：人体的气有清和浊的区别，受纳于自然界清气的是清气的来源。清气注入阴经，所以上行注入手太阴肺经，其气运行滑利；但清气中也有浊的部分，清中之浊下行进入经脉，内聚于海（指气海或血海等）。所有阴经都主清气，足部阴经之气下行走向胃（足阳明胃经），其气运行涩滞；浊气中也有清的部分，浊中之清上行出于咽喉和口。所有阳经都主浊气，只有手太阳小肠经单独承受这种浊气，这是阳气中浊气特别盛重的表现（此段文字依次引用自《阴阳清浊》篇）。
《素问》说：邪气亢盛就表现为实证，精气耗损就表现为虚证。寸口脉急而尺部脉缓的，说明经络都是实证。脉口（即寸口）发热而尺部寒冷的，说明络脉虚而经脉实。尺部脉满实，脉口寒冷涩滞的，说明经脉虚而络脉满实（“满”即“实”的意思）。大热病患者，如果气息粗促且脉象满实的，属于重实证（气和脉都表现为实）。脉虚（经文说：脉虚者，不象阴也。然而气口是脉诊的要会，是手太阴肺经动脉所在，所以说不象阴是指脉不应象阴脉之象）、气虚（经文说：气虚者无常也。指的是膻中之气不稳定，旧注认为寸脉跳动无常的不是这个意思）、尺部虚弱的（行走时步履不稳），属于重虚证（此段概括自《通评虚实论篇》的文字）。
《难经》说：疾病有虚和实两种性质，病邪由内向外发的为虚，由外向内入的为实（从体内到体外称为出，从体外到体内称为入）。能言语的为虚，不能言语的为实（能言语是指患病但还能说话，不能言语是指患病且无法说话）。脉势缓和的为虚，脉势紧急的为实（这里的缓急是指病势而言）。脉象有虚实之分，濡脉者为虚，紧脉、牢脉者为实（濡脉，属阴金，按之似有，轻举若无；紧脉，属阳木，按之有余，轻举甚数，状如洪弦，三关通达；牢脉，属阴木，寻之即无，按之却有，沉而有力，动而不移）。诊察有虚实之分（诊，即视验，是探求病情的通称，兼含望、闻、问、切四诊），濡脉者为虚，牢脉者为实（濡脉和牢脉虽然与脉象相似，但这里所指的范围更广）；瘙痒的为虚，疼痛的为实（气欲通畅则痒，不通畅则痛）；外部通畅内部爽快，为外实内虚；内部疼痛外部爽快，为内实外虚（“快”意为爽快舒适），这被称为三虚和三实（凡是说虚的，是指精气耗损；说实的，是指邪气亢盛）。（此段依次引用自《四十八难》的文字）
《素问》又说：五实死，五虚死（“五”指五脏）。脉象盛大（心实），皮肤发热（肺实），腹部胀满（脾实），大小便不通（肾实），胸闷昏乱（肝实），这叫做五实；脉象细弱（心虚），皮肤寒冷（肺虚），气短少（肝虚），大小便泄利不止（肾虚），饮食无法入口（脾虚），这叫做五虚。然而有时却能存活，为什么呢？如果浆粥能进入胃中，泄泻停止，那么虚证患者就能活；如果身体出汗，大便通畅，那么实证患者就能活（此段稍后引用自《玉机真藏论篇》的文字）。
The *Ling Shu* (Spiritual Pivot) states: Human Qi has distinctions of clear (Qing) and turbid (Zhuo). The source of receiving clear Qi is clear. Clear Qi enters the Yin meridians, thus ascending to the Lung (Hand-Taiyin), where its movement is smooth; however, within the clear Qi there is a turbid component. This clear-yet-turbid Qi descends into the meridians and accumulates internally in the Sea (referring to Qi or Blood Seas). All Yin meridians govern clear Qi, with foot Yin Qi descending towards the Stomach (Foot-Yangming), where its movement is sluggish; yet within the turbid Qi there is a clear component. This turbid-yet-clear Qi ascends to emerge from the pharynx and mouth. All Yang meridians govern turbid Qi, but only the Small Intestine (Hand-Taiyin) alone receives this turbidity, indicating that turbidity in Yang Qi is exceptionally severe (this passage follows the text from the "Clear and Turbid" chapter).
The *Su Wen* (Basic Questions) states: When pathogenic factors are exuberant, it manifests as Excess (Shi); when essential Qi is depleted, it manifests as Deficiency (Xu). If the Cun pulse is rapid/tight while the Chi pulse is slow/relaxed, both the meridians and collaterals are in an Excess state. If the Maikou (pulse opening, i.e., Cun Kou) feels hot while the Chi area feels cold, the collaterals are Deficient while the meridians are Excess. If the Chi pulse is full/excessive and the Maikou is cold and choppy, the meridians are Deficient while the collaterals are Full/Excess ("Full" means "Excess"). In patients with high fever, if the breath is hot/raspy and the pulse is full, it constitutes a Heavy Excess condition (both Qi and pulse indicate Excess). A deficient pulse (The classic states: "A deficient pulse does not resemble Yin." However, the Maikou is the crucial meeting point for pulse diagnosis and the site of the Hand-Taiyin artery's movement; thus, "not resembling Yin" refers to the pulse not exhibiting typical Yin characteristics), deficient Qi (The classic states: "Deficient Qi is irregular/unstable." This refers to instability in the Qi of the Danzhong; old annotations incorrectly attributed this to irregular pulsation at the Cun position), and deficient Chi (walking with unsteadiness) constitute a Heavy Deficiency condition (this section summarizes text from the "General Discussion on Excess and Deficiency" chapter).
The *Nan Jing* (Classic of Difficult Issues) states: Diseases have nature of Deficiency and Excess. Pathogens moving outward are Deficiency; pathogens moving inward are Excess (moving from interior to exterior is called "outward"; moving from exterior to interior is called "inward"). Ability to speak indicates Deficiency; inability to speak indicates Excess (ability to speak means the patient is ill but can still talk; inability to speak means the patient is ill and cannot talk). A relaxed/slow pulse indicates Deficiency; a tight/urgent pulse indicates Excess (relaxation and urgency refer to the progression of the disease). Pulse qualities distinguish Deficiency and Excess: a soggy (Ru) pulse indicates Deficiency, while tight (Jin) and firm (Lao) pulses indicate Excess (A Ru pulse belongs to Yin Metal; felt faintly upon pressure, absent upon light lifting. A Jin pulse belongs to Yang Wood; feels abundant upon pressure, frequent upon light lifting, resembling a flood or string quality, penetrating all three positions. A Lao pulse belongs to Yin Wood; disappears upon searching, appears upon pressing, deep and forceful, moving without shifting). Diagnosis distinguishes Deficiency and Excess (Diagnosis involves visual inspection and verification, a general term for probing illness, encompassing observation, listening/smelling, inquiry, and palpation). A soggy pulse indicates Deficiency, a firm pulse indicates Excess (although Ru and Lao resemble pulse qualities, the scope here is broader); itching indicates Deficiency, pain indicates Excess (itching occurs when Qi desires to flow freely; pain occurs when flow is obstructed). External openness with internal comfort indicates External Excess and Internal Deficiency; internal pain with external comfort indicates Internal Excess and External Deficiency ("Comfort" implies a sense of ease). These are referred to as Three Deficiencies and Three Excesses (Whenever "Deficiency" is mentioned, it refers to depletion of essential Qi; whenever "Excess" is mentioned, it refers to exuberance of pathogenic Qi). (This section follows the text from the Forty-Eighth Difficulty).
The *Su Wen* further states: Five Excesses lead to death, Five Deficiencies lead to death ("Five" refers to the five Zang organs). A surging pulse (Heart Excess), hot skin (Lung Excess), abdominal distension (Spleen Excess), obstruction of urination and defecation (Kidney Excess), chest stuffiness and dizziness (Liver Excess)—these constitute Five Excesses. A fine/thin pulse (Heart Deficiency), cold skin (Lung Deficiency), shortness of breath (Liver Deficiency), diarrhea and incontinence (Kidney Deficiency), inability to ingest food/drink (Spleen Deficiency)—these constitute Five Deficiencies. Yet sometimes survival occurs; why? If gruel and porridge enter the Stomach and diarrhea stops, the Deficient patient survives; if sweat is produced and bowels move freely, the Excess patient survives (this section slightly follows the text from the "Discussion on True Viscera Pulses" chapter).