或问曰∶医道至繁，何以得其要领，而执简以驭繁也？余曰∶病不在人身之外，而在人
身之中。子试静坐内观，从头面推想，自胸至足，从足跟推想，自背至头；从皮肉推想，内
至筋骨脏腑，则全书之目录，在其中矣。凡病之来，不过内伤、外感，与不内外伤，三者而
己。内伤者，气病、血病、伤食，以及喜、怒、忧、思、悲、恐、惊是也。外感者，风、寒
、暑、湿、燥、火是也。不内外伤者，跌打损伤、五绝之类是也。病有三因，不外此矣。至
于变症百端，不过寒、热、虚、实、表、里、阴、阳八字尽之，则变而不变矣。论治法，不
过七方与十剂。七方者，大、小、缓、急、奇、偶、复，十剂者，宣、通、补、泻、轻、重
、滑、涩、燥、湿也。精乎此，则投治得宜矣。又外感之邪，自外而入，宜泻不宜补。内伤
之邪，自内而出，宜补不宜泻。然而泻之中有补，补之中有泻，此皆治法之权衡也。又有
似症，如火似水，水似火，金似木，木似金，虚似实，实似虚，不可以不辨。明乎此，则病
无遁情矣。学人读书之余，闭目凝神，时刻将此数语，细加领会，自应一旦豁然，融会贯通
彻始彻终，了无疑义，以之司命奚愧焉。
人身之病，不离乎内伤、外感，而内伤、外感中，只一十九字尽之矣。如风、寒、暑、
湿、燥、火，外感也。喜、怒、忧、思、悲、恐、惊，与夫阳虚、阴虚、伤食，内伤也。总
计之，共一十九字，而千变万化之病，于以出焉。然病即变化，而总不离乎一十九字，一十
九字总之，一内伤、外感而已。所谓知其要者，一言而终，不知其要，流散无穷。此道中必
须提纲挈领，然后拯救有方也。
有人问道：医学的道理非常繁杂，怎样才能掌握其要领，从而以简驭繁呢？我回答说：疾病并不在人身之外，而是在人身之中。你试着静坐内观，从头面部开始推想，从胸部推到足部，从足跟推想，从背部推到头部；从皮肉推想，向内深入到筋骨脏腑，那么整本书的目录，就包含在其中了。凡是疾病的产生，不外乎内伤、外感，以及不内外伤这三类罢了。所谓内伤，是指气病（气的病变）、血病（血的病变）、伤食（饮食积滞），以及喜、怒、忧、思、悲、恐、惊这七种情志致病因素。所谓外感，是指风、寒、暑、湿、燥、火这六淫邪气。所谓不内外伤，是指跌打损伤、五绝（指窒息、溺死等五种致死急症）之类的病因。疾病虽有三种成因，但不超出这些范围。至于各种变幻莫测的症状，不过用寒、热、虚、实、表、里、阴、阳这八个字就能概括尽致，这样变化也就有了不变的规律。论述治疗方法，不过是“七方”和“十剂”。所谓七方，是指大、小、缓、急、奇、偶、复；所谓十剂，是指宣、通、补、泻、轻、重、滑、涩、燥、湿。精通于此，治疗用药就能得当。另外，外感的邪气，是从外部侵入人体，适宜用泻法而不适宜用补法。内伤的邪气，是从内部产生的，适宜用补法而不适宜用泻法。然而，在泻法中包含着补意，在补法中也包含着泻意，这些都是治疗方法的权衡运用。又有似是而非的症状，如火似水，水似火，金似木，木似金，虚似实，实似虚，不可以不加以辨别。明白了这些，疾病就没有隐瞒的情况了。学医的人在读书之余，闭目凝神，时刻将这些话语细细领会，自然会在某一天豁然开朗，融会贯通，彻始彻终，没有任何疑问，以此来掌管人的生死，又有什么可惭愧的呢？
人身上的疾病，离不开内伤和外感，而在内伤和外感中，只用十九个字就能概括尽了。如风、寒、暑、湿、燥、火，属于外感。喜、怒、忧、思、悲、恐、惊，以及阳虚（阳气不足）、阴虚（阴液亏虚）、伤食，属于内伤。总计起来，共十九个字，而千变万化的疾病，由此产生。然而疾病虽然变化多端，但总不离乎这十九个字，这十九个字总括起来，就是内伤和外感而已。所说的“知道要领的人，一句话就能终结道理；不知道要领的人，就会流散无穷无尽”，这条道路必须提纲挈领，然后拯救病人才能有所依据。
A question was asked: "The principles of medicine are extremely complex; how can one grasp the essentials to manage the complexity with simplicity?" I replied: "Diseases do not exist outside the human body, but within it. Try sitting quietly and observing inwardly. Visualize from the head and face, extending down from the chest to the feet, and from the soles of the feet upward to the back and head; visualize from the skin and flesh, penetrating inward to the sinews, bones, and zang-fu organs. In doing so, the outline of the entire medical text will be revealed." The onset of any disease falls into only three categories: internal injury (internal damage), external contraction (external invasion), and neither-internal-nor-external injury. Internal injuries include qi disorders (disorders of Qi), blood disorders (disorders of Blood), food stagnation (food retention), and the seven emotions: joy, anger, worry, thought, sorrow, fear, and fright. External contractions refer to the six climatic pathogens: wind, cold, summerheat, dampness, dryness, and fire. Neither-internal-nor-external injuries include traumatic injuries and conditions such as the five types of sudden death (wujue). Although there are three causes of disease, they do not exceed these categories. As for the myriad variations in symptoms, they can all be summarized by eight characters: cold, heat, deficiency, excess, exterior, interior, yin, and yang. Thus, change is governed by constancy. Regarding treatment methods, they are essentially categorized into the Seven Formulas (qifang) and the Ten Agents (shiji). The Seven Formulas are: large, small, slow, urgent, single, paired, and compound. The Ten Agents are: dispersing, unblocking, tonifying, purging, light, heavy, slippery, astringent, drying, and moistening. Mastery of these ensures appropriate therapeutic intervention. Furthermore, pathogenic factors of external contraction enter from the outside and should be treated with purgation rather than tonification. Pathogenic factors of internal injury arise from within and should be treated with tonification rather than purgation. However, tonification contains elements of purgation, and purgation contains elements of tonification; these represent the balancing acts of treatment methods. One must also distinguish between deceptive similarities, such as fire resembling water, water resembling fire, metal resembling wood, wood resembling metal, deficiency resembling excess, and excess resembling deficiency. Understanding these distinctions leaves no room for disease to conceal its true nature. Students of medicine, after reading, should close their eyes, concentrate their spirit, and constantly reflect deeply on these words. Eventually, they will experience a moment of sudden enlightenment, integrating knowledge thoroughly and comprehensively, leaving no doubts. With this mastery, how could one feel ashamed in managing life and death?
Diseases of the human body are inseparable from internal injury and external contraction. Within these two categories, nineteen characters suffice to summarize them all. For example, wind, cold, summerheat, dampness, dryness, and fire constitute external contraction. Joy, anger, worry, thought, sorrow, fear, fright, along with yang deficiency (yang xu), yin deficiency (yin xu), and food stagnation constitute internal injury. In total, there are nineteen characters, from which the thousands of transformations of disease arise. Although diseases vary infinitely, they ultimately revolve around these nineteen characters, which boil down to just internal injury and external contraction. As the saying goes, "He who knows the essence needs but one word to conclude; he who does not know the essence wanders endlessly." In this field, one must grasp the main points to provide effective rescue.