医之为学，其道博，其义深，其书浩瀚，其要不过阴阳五行而已。盖天以阴阳五行，化
生万物。其禀于人身者，阴阳之气，以为血气表里上下之体；五行之气，以为五脏六腑之质
。由是人身具足而有生焉。然阴阳错综，五行迭运，不能无浓薄多少之殊。故禀阴阳五行之
气浓者，血气脏腑壮而无病；薄者，血气脏腑怯而有病。阳多者，火多，性急而形瘦；阴多
者，湿多，性缓而形肥。阳少者，气虚、表虚、上虚，而易于外感；阴少者，血虚、里虚、
下虚，而易于内伤。况乎人以易感、易伤之躯，徇情纵欲，不适寒温，由是正损邪客，而阴
阳脏腑愈虚愈实，或寒或热，而百病出焉。故诊病者，必先分别血气表里上下脏腑之分野，
以知受病之所在；次察所病虚实寒热之邪以治之。务在阴阳不偏倾，脏腑不胜负，补泻随宜
，适其病所，使之痊安而已。然其道自轩、岐而下，仲景详外感于表里阴阳，丹溪独内伤于
血气虚实，东垣扶护中气，河间推陈致新，钱氏分明五脏，戴人熟施三法，凡历代方书甚众
，皆各有所长耳。故后世用历代之方治病，或效、或不效者，由病名同、治法异，或中其长
，或不中其长故也。姑举一病言之，设恶热病，热病之名同也，其治之法异，四君治血实之
热也，四物治血虚之热也，白虎治气实之热也，补中治气虚之热也，麻黄治表热也，承气治
里热也，四逆治假热也，柴胡治真热也，泻青、导赤、泻白、滋肾、泻黄治五脏热而各异也
，各能洞烛脉证，而中其肯綮，则皆效。其或实用虚法，虚用实法，表用里法，里用表法，
真用假法，假用真法，则死生反掌之间，尚何责其效乎。昧者不悟是理，泛用古今之方，妄
试疑似之病，每致夭横者不少矣。若是者，虚窃济生之名，实所以害人之生，乱医之真，孔
子以乡愿乱德为德之贼，斯则医之贼也。暗损阴骘，神明不佑，可不谨哉！英爰自髫年，潜
心斯道，上自《内经》，下至历代圣贤书传，及诸家名方，昼读夜思，废餐忘寝者三十余载
，始悟千变万化之病态，皆不出乎阴阳五行。盖血气也，表里也，上下也，虚实也，寒热也
，皆一阴阳也；五脏也，六腑也，十二经也，五运六气也，皆一五行也。鳞集于鱼，辐辏于
毂，医之能事毕矣。是以不揣芜陋，掇拾经传方书，一以阴阳脏腑分病析法而类聚之。分病
为门，门各定阴阳脏腑之部于其卷首而大纲着矣。析法为标，标各撮阴阳脏腑之要于其条上
，而众目彰矣。病有同其门者，立枝门以附之；法有同其标者，立细标以次之。凡经有衍文
错简脱简者，一以理考而释正之。传失经旨，众论矛盾者，各以经推而辨明之。庶几诸家之
同异得失，得以曲畅旁通，精粗相因，巨细毕举，同病异法，如指诸掌，名之曰《医学纲目
》。藏之巾笥，以便考求，使夫临病之际，自然法度有归，不致误投汤剂，而害生乱医，获
罪神明者矣。虽于轩岐心法之妙，不敢同年而语，然亦天地生物之心一助云耳。
萧山仙居岩楼英全善撰
医学这门学问，其道理广博，其含义深远，其著作浩如烟海，但其核心要点不过在于阴阳和五行罢了。大概上天凭借阴阳五行，化生出万物。这些禀受于人身上的，是阴阳之气，构成了血气、表里、上下之形体；是五行之气，构成了五脏六腑之实质。因此人体具备这些要素而得以生存。然而阴阳错综复杂，五行交替运行，不能没有浓淡、多少的差异。所以禀受阴阳五行之气浓厚的人，血气和脏腑强壮而没有疾病；禀受之气薄弱的人，血气和脏腑怯弱而有疾病。阳气多的人，火气多，性格急躁且身形消瘦；阴气多的人，湿气多，性格迟缓且身形肥胖。阳气少的人，气虚、表虚、上虚，容易遭受外邪侵袭；阴气少的人，血虚、里虚、下虚，容易遭受内伤。况且人们以这种容易感邪、容易受伤的身体，放纵情欲，不适应寒温变化，因此正气受损、邪气客居，导致阴阳脏腑越来越虚弱或实滞，或寒或热，从而百病丛生。所以诊治疾病的人，必须先分别清楚血气、表里、上下、脏腑的界限，以知道病变所在之处；其次观察所患疾病的虚实寒热之邪来进行治疗。务必使阴阳不偏颇倾斜，脏腑不相互克制失衡，补泻随宜，适合病情所在，使之痊愈安康罢了。然而这条道统从黄帝、岐伯开始，张仲景详细论述了外感病在表里阴阳方面的辨证，朱丹溪专门论述内伤病在血气虚实方面的辨证，李东垣扶持保护中气，刘河间推陈致新，钱乙明确区分五脏病症，张从正熟练运用汗、吐、下三法，凡是历代方书非常多，都各有长处罢了。所以后世使用历代的方剂治病，有的有效、有的无效，是因为病名相同但治法不同，或者抓住了长处的优点，或者没有抓住长处的原因。姑且举一种病来说明，假设是恶热病，“热病”这个名称是相同的，但治疗方法各异：四君子汤治疗血实之热，四物汤治疗血虚之热，白虎汤治疗气实之热，补中益气汤治疗气虚之热，麻黄汤治疗表热，承气汤治疗里热，四逆汤治疗假热，柴胡剂治疗真热，泻青丸、导赤散、泻白散、滋肾丸、泻黄散治疗五脏之热而各不相同。如果能洞察脉象和证候，切中要害，那么都能见效。如果实证用虚法，虚证用实法，表证用里法，里证用表法，真热用假法治，假热用真法治，那么在生死反掌之间，还怎么要求它见效呢？愚昧的人不明白这个道理，广泛使用古今的方剂，妄自尝试症状相似的疾病，常常导致早逝的情况不少。像这样的人，窃取了济世救人的名声，实际上却害人性命，扰乱了医学的真谛。孔子认为乡愿（看似忠厚老实实则同流合污的人）混淆道德，是道德的贼寇，这些人则是医学的贼寇。暗中损害阴德，神明不会保佑，能不谨慎吗！我楼英从童年起，就潜心钻研此道，上至《黄帝内经》，下至历代圣贤的书传，以及各家的名方，白天阅读晚上思考，废寝忘食三十多年，才领悟到千变万化的病态，都不超出阴阳五行的范围。大概血气、表里、上下、虚实、寒热，都是一阴一阳的表现；五脏、六腑、十二经脉、五运六气，都是一五行的表现。就像鱼鳞聚集在一起，车轮辐条汇聚于毂，医者的能事就完成了。因此我不揣冒昧，收集经传方书，一律以阴阳脏腑来分病析法并归类聚集。将疾病分为门类，每卷之首确定该门的阴阳脏腑分部，这样大纲就明确了。将治法列为标目，每条之上摘录阴阳脏腑的要领，这样众目就清晰了。有属于同一门类的疾病，设立分支门附属于主门之下；有属于同一标目的治法，设立细标目依次排列。凡是经典中有衍文、错简、脱简的地方，一律依据医理考证并纠正。对于违背经典主旨、众论矛盾的地方，各自依据经典推导并辨明。希望各家学说的异同得失，能够详尽通畅，精粗相因，大小毕举，同病异法，如同指掌般清晰，命名为《医学纲目》。收藏在书箱中，以便查阅考究，使得在面对疾病时，自然有法度可依，不至于误投汤药，从而害人性命、扰乱医学、获罪神明。虽然不敢与黄帝、岐伯的心法妙义相提并论，但也算是为天地好生之心尽了一份助力罢了。
萧山仙居岩楼英全善撰
The study of medicine is broad in scope, profound in meaning, and vast in literature, yet its essence lies merely in Yin-Yang and the Five Elements. Heaven generates all things through Yin-Yang and the Five Elements. In the human body, the Qi of Yin-Yang forms the structure of blood-Qi, exterior-interior, and upper-lower; the Qi of the Five Elements constitutes the substance of the Zang-Fu organs. Thus, endowed with these elements, life exists. However, as Yin-Yang interweave and the Five Elements cycle, there are inevitably differences in density and quantity. Those who receive dense Qi of Yin-Yang and the Five Elements possess robust blood-Qi and Zang-Fu organs and remain disease-free; those who receive thin Qi suffer from weakness in blood-Qi and Zang-Fu organs and fall ill. Excess Yang implies excess Fire, leading to an irritable temperament and emaciated physique; excess Yin implies excess Dampness, leading to a sluggish temperament and obesity. Deficiency of Yang results in Qi deficiency, Exterior deficiency, and Upper deficiency, making one susceptible to external pathogens; deficiency of Yin results in Blood deficiency, Interior deficiency, and Lower deficiency, making one susceptible to internal injury. Moreover, with such a vulnerable constitution, people indulge their desires and fail to adapt to cold and heat. Consequently, healthy Qi is damaged and pathogenic factors invade, causing the Yin-Yang and Zang-Fu organs to become increasingly deficient or stagnant, alternating between Cold and Heat, thereby giving rise to myriad diseases. Therefore, when diagnosing illness, one must first distinguish the domains of blood-Qi, exterior-interior, upper-lower, and Zang-Fu to locate the pathology; then observe the pathogenic factors of deficiency-excess and Cold-Heat to treat them. The goal is to ensure Yin-Yang do not deviate, Zang-Fu do not overcome each other excessively, and tonification or purgation is applied appropriately to suit the condition, aiming solely for recovery. This lineage traces back to Huangdi (Yellow Emperor) and Qibo. Zhang Zhongjing detailed the differentiation of external contraction diseases regarding exterior-interior and Yin-Yang; Zhu Danxi focused on internal injury regarding blood-Qi and deficiency-excess; Li Dongyuan supported and protected Middle Qi; Liu Wanshu promoted eliminating the old and generating the new; Qian Yi clearly differentiated Zang organ diseases; Zhang Congzheng skillfully applied the three methods (sweating, vomiting, purging). Numerous medical texts from past dynasties exist, each possessing its own strengths. Hence, when later generations use formulas from various dynasties to treat diseases, efficacy varies because while disease names may be identical, treatment methods differ; sometimes the strength is utilized, sometimes it is not. Taking "heat disease" as an example: the name is the same, but treatments vary. Sijunzi Tang (Four Gentlemen Decoction) treats heat due to Blood excess; Siwu Tang (Four Substance Decoction) treats heat due to Blood deficiency; Baihu Tang (White Tiger Decoction) treats heat due to Qi excess; Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction) treats heat due to Qi deficiency; Mahuang Tang (Ephedra Decoction) treats Exterior heat; Chengqi Tang (Descending Qi Decoction) treats Interior heat; Sini Tang (Frigid Extremities Decoction) treats false heat; Chaihu preparations treat true heat; Xieqing Wan (Drain Green Pill), Daochi San (Direct to the Heart Powder), Xiebai San (Drain White Powder), Zishen Wan (Nourish Kidney Pill), and Xiehuang San (Drain Yellow Powder) treat heat in the five Zang organs differently. If one can penetrate the pulse and symptoms and hit the critical point, all will be effective. However, using deficiency-methods for excess conditions, excess-methods for deficiency conditions, exterior-methods for interior conditions, interior-methods for exterior conditions, true-methods for false conditions, or false-methods for true conditions, life and death hang in the balance; how could one expect efficacy? Ignorant practitioners fail to grasp this principle, indiscriminately using ancient and modern formulas on similar-looking diseases, often resulting in premature death. Such individuals steal the reputation of saving lives but actually harm life and distort the truth of medicine. As Confucius stated that the "man of good character" (Xiangyuan) corrupts virtue and is the thief of virtue, these individuals are the thieves of medicine. They secretly damage their moral merit, and spirits will not bless them; can they not be cautious? Since childhood, I, Lou Ying, have devoted myself to this path. From the *Neijing* (Inner Canon) down to the writings of sages from all dynasties and famous formulas from various schools, I read by day and pondered by night, neglecting meals and sleep for over thirty years. Only then did I realize that the thousands of variations in pathological states do not exceed Yin-Yang and the Five Elements. Blood-Qi, exterior-interior, upper-lower, deficiency-excess, and Cold-Heat are all manifestations of one Yin and one Yang; the five Zang organs, six Fu organs, twelve meridians, and the Five Movements and Six Qi are all manifestations of the Five Elements. Like fish scales gathering or spokes converging on a hub, the art of medicine is complete. Therefore, without presuming upon my humble abilities, I have collected canonical texts and medical books, classifying and grouping diseases and methods based on Yin-Yang and Zang-Fu. Diseases are divided into chapters, with the Yin-Yang and Zang-Fu categories defined at the beginning of each volume to establish the main outline. Methods are listed as subheadings, with key points of Yin-Yang and Zang-Fu summarized above each item to clarify the details. For diseases sharing a chapter, branch chapters are established to attach them; for methods sharing a subheading, finer subheadings are created to order them. Where classics contain redundant text, misplaced slips, or missing slips, I verify and correct them according to medical principles. Where commentaries lose the original intent of the classics or theories contradict each other, I deduce and clarify them based on the classics. Thus, the similarities, differences, merits, and faults of various schools can be thoroughly understood, connecting fine and coarse aspects, covering major and minor points comprehensively, making different treatments for the same disease clear as palm reading. I named this work *Yixue Gangmu* (Outline of Medical Science). It is stored in a book box for easy reference, ensuring that when facing illness, one naturally has rules to follow, avoiding misprescription of decoctions that would harm life, distort medicine, and incur the wrath of the spirits. Although I dare not compare myself to the profound mind-methods of Huangdi and Qibo, this effort serves as a small contribution to the creative heart of Heaven and Earth.
Lou Ying Quanshan of Xianshan Xianju Yan wrote this.