夫医理之无尽。犹之儒业。第文之不工。费其纸。医之不工。费其人。大相越
也。盖古来生知者一二人。然炎帝之于百草。尝而后知。轩辕之于经络。问
而始悉。所谓上窍天纪。下极地理。中知人事。使非有以穷之极之。而能知
之哉。后此名流递出。无不根究理道。参物类而尽性命。而后以术鸣当时。
名垂奕祀。况下此者。智不及古人。而不穷搜博览。罕所见于中。辄以人命
自司。其不偾溃者几希。故昔贤云。读十年书。无病不可疗。更读十年书。无
病可疗。知言哉。
凡病可以意料也。而不可以意逆。料则任彼之情形。逆则执己之臆见。有
如素实者。而有一时之虚。则暂理其虚。素虚者。而有一时之实。则微解其
实。此机之从缓者也。实症而攻之过甚。宜峻补以挽之。虚症而补之太骤。
宜平剂以调之。此机之从急者也。热者清之。及半即止。继以益阴。寒者热
之。大半即安。继以调和。此机之从权者也。实症久而似虚。其中有实。不任
受补。虚症发而似实。其原本虚。不任受克。此机之从经者也。病在上。下取
之。阳根于阴。病在下。上取之。阴从于阳。此机之从本者也。表症见。本质虽
虚。犹解其表。里症见。元气纵弱。犹攻其里。此机之从标者也。况乎病之来
也无方。而我之应之也亦无方。千变而出之以万虑。有能遁其情者无之。
医理是无穷无尽的，就像儒家的学问一样。文章写得不好，浪费的是纸张；医术不精，浪费的是人命。这两者相差太远了。自古以来，天生就通晓医道的人不过一两个。但是炎帝对于百草，也是尝过之后才知道药性；轩辕黄帝对于经络，也是询问之后才完全了解。这就是所说的上通天文，下究地理，中知人事。如果不是深入探究到极致，怎么能真正懂得呢？此后名医相继出现，无不根究医理大道，参悟万物类别以穷尽生命规律，然后凭借医术闻名于当时，美名流传百代。何况才智不如古人的人，如果不广泛搜集、博览群书，心中很少有所见地，却把人的性命当作自己的责任来掌管，他们不出差错崩溃的情况是很少见的。所以以前的贤人说：“读十年书，没有治不好的病；再读十年书，发现没有能治好的病。”这真是至理名言啊。
一般的疾病是可以推测的，但不可以主观臆断。推测是根据病人的具体情况来判断，臆断则是固执于自己的主观见解。例如平时体质充实的人，如果出现一时的虚弱症状，就暂时调理其虚证；平时体质虚弱的人，如果出现一时的实证，就轻微解除其实证。这是顺应病情变化而采取缓和策略的方法。实证如果攻伐太过，应当用峻猛的补剂来挽回；虚证如果补益太急骤，应当用平和的药剂来调和。这是应对紧急情况的策略。热证用清热法，用到一半就停止，接着用滋阴的方法；寒证用温热法，用到大部分见效后就停止，接着用调和的方法。这是权变灵活处理的策略。实证久了看起来像虚证，但其中仍有实邪，不能承受补益；虚证发作时看起来像实证，但其本质是虚，不能承受攻伐。这是遵循常规法则的策略。病在上部，从下部取穴治疗，因为阳根于阴；病在下部，从上部取穴治疗，因为阴从于阳。这是追溯根本的策略。表证出现，虽然本质虚弱，仍然先解表；里证出现，虽然元气衰弱，仍然先攻里。这是处理标急的策略。况且疾病的变化没有固定的模式，我们应对疾病也没有固定的模式。千变万化，都要通过周密的思虑来处理，能够逃脱病情真实情况的人是找不到的。
The principles of medicine are endless, just like the studies of Confucianism. If an essay is poorly written, paper is wasted; if medical practice is incompetent, human lives are wasted. The difference between these two is vast. Since ancient times, there have been only one or two individuals born with innate knowledge. However, Shennong (Yandi) knew the properties of hundreds of herbs only after tasting them; Xuanyuan (Huangdi) fully understood the meridians only after inquiring about them. This is what is meant by "understanding heavenly patterns above, earthly geography below, and human affairs in the middle." Unless one explores to the utmost limit, how can one truly understand? Later, famous doctors emerged successively, all of whom investigated the fundamental principles of medicine, studied the categories of things to exhaust the laws of life, and thereby became renowned for their skills in their time, leaving their names for generations. How much more so for those whose wisdom is inferior to that of the ancients? If they do not extensively search and read broadly, having little insight within, yet presume to manage human lives, it is rare that they would not fail or collapse. Therefore, the sages of old said, "After studying for ten years, there is no disease that cannot be cured; after studying for another ten years, one realizes there are diseases that cannot be cured." These are words of truth.
General diseases can be anticipated but should not be guessed at subjectively. Anticipation relies on the patient's specific condition, whereas subjective guessing clings to one's own preconceived notions. For instance, a person who is usually robust may experience temporary deficiency; in such cases, the deficiency should be temporarily regulated. A person who is usually deficient may experience temporary excess; in such cases, the excess should be slightly resolved. This is the strategy of adopting a缓 (slow/gentle) approach to the changing situation. If an Excess syndrome is treated with excessive purgation, it should be rescued with strong tonification. If a Deficiency syndrome is treated with overly rapid tonification, it should be regulated with mild formulas. This is the strategy for urgent situations. For Heat syndromes, use clearing methods until halfway, then stop and follow with Yin-nourishing methods. For Cold syndromes, use warming methods until mostly resolved, then stop and follow with harmonizing methods. This is the strategy of flexibility (Quan). When an Excess syndrome persists for a long time and appears like Deficiency, there is still excess within, and it cannot tolerate tonification. When a Deficiency syndrome flares up and appears like Excess, its root is Deficiency, and it cannot tolerate attack/clearing. This is the strategy of following standard principles (Jing). For diseases located in the upper part, treat from the lower part, because Yang roots in Yin; for diseases located in the lower part, treat from the upper part, because Yin follows Yang. This is the strategy of addressing the root (Ben). When Exterior syndromes appear, even if the constitution is weak, the exterior should still be released; when Interior syndromes appear, even if Yuan Qi is weak, the interior should still be attacked. This is the strategy of addressing the branch/biao (Biao). Moreover, the onset of disease has no fixed pattern, and our response to it also has no fixed pattern. With thousands of changes handled through ten thousand considerations, there is no one who can escape the true nature of the illness.