仲景之学，至唐而一变。仲景之治病，其论脏腑经络，病情传变，悉本《内经》。而其
所用
之方，皆古圣相传之经方，并非私心自造，间有加减，必有所本。其分两轻重，皆有法度。
其药悉本于《神农本草》，无一味游移假借之处。非此方不能治此病，非此药不能成此方，
粗微深妙，不可思议。药味不过五六品，而功用无不周。此乃天地之化机，圣人之妙用与天
地同。不朽者也。《千金方》则不然，其所论病，未尝不根据《内经》，而不无杂以后世臆度
之说。其所用方，亦皆采择古方，不无兼取后世偏杂之法。其所用药，未必全本于《神农》
，兼取杂方单方，及通治之品。故有一病而立数方，亦有一方而治数病。其药品有多至数十
味者，其中对症者固多，不对症者亦不少，故治病亦有效有不效。大抵所重，专在于药，而
古圣制方之法不传矣。此医道之一大变也。然其用药之奇，用意之巧，亦自成一家，有不可
磨灭之处。至唐·王焘所集《外台》一书，则纂集自汉以来诸方，汇萃成书，而历代之方，
于焉大备。但其人本非专家之学，故无所审择，以为指归，乃医方之类书也。然唐以前之方
，赖此书以存，其攻亦不可泯。但读之者，苟胸中无成竹，则众说纷纭，群方淆杂，反茫然
失其所据。故读《千金》《外台》者，必精通于《内经》、仲景、本草等书，胸中先有成见
，而后取其长而舍其短，则可资我博深之益。否则反乱人意，而无所适从。嗟乎！《千金》
、《外台》且然，况后世偏驳杂乱之书，能不惑人之心志哉？等而下之，更有无稽杜撰之邪
书，尤不足道矣。
张仲景的医学理论，到了唐代发生了一次重大变革。张仲景治疗疾病时，其关于脏腑经络、病情传变的论述，完全依据《黄帝内经》。而他所使用的方剂，都是古代圣贤传承下来的经方，并非凭个人私意自行创造，即使偶尔有加减变化，也必定有所本原。其中药物的分量轻重，都有严格的法度规范。所用药物全部依据《神农本草经》，没有一味药是随意借用或模棱两可的。不是这个方子就不能治疗这个病，不是这些药就不能组成这个方子，其细微与深奥精妙之处，令人不可思议。药味不过五六种，但功效却无所不包。这是天地化育万物的机理，圣人运用之妙与天地相同，是不朽的经典。
《千金方》则不然，它所论述的疾病，虽然未尝不根据《黄帝内经》，但不免夹杂后世主观臆测的说法。它所使用的方剂，也是采集选取古方，但不免兼取后世偏颇杂乱的方法。它所使用的药物，未必完全依据《神农本草经》，还兼取杂方单方以及通用治疗的物品。因此，有一种病设立多个方剂，也有一个方剂治疗多种疾病的情况。其中的药品数量多至几十味，其中对症的药固然很多，不对症的也不少，所以治疗效果也是有的有效，有的无效。大体上，《千金方》所重视的专门在于药物种类，而古代圣贤制定方剂的法则已经失传了。这是医道的一次重大变革。然而，它用药的奇特，用意的巧妙，也自成一家，有不可磨灭的价值。
到了唐代王焘编纂的《外台秘要》一书，则是汇集收集自汉代以来的各种方剂，汇编成书，于是历代的方剂在此书中大为完备。但是，王焘本人并非医学专家之学，所以没有经过审慎的选择，以确立宗旨，这只是一部医方的类书罢了。然而，唐代以前的方剂，依靠这本书得以保存，它的功劳也不可抹杀。只是读书的人，如果胸中没有成熟的见解（成竹），那么面对众说纷纭、群方混杂的情况，反而会茫然失去依据。所以，阅读《千金方》和《外台秘要》的人，必须精通《黄帝内经》、张仲景著作、《神农本草经》等书籍，胸中先有成见，然后取其长处舍弃短处，才可以借助它们获得广博深厚的益处。否则反而扰乱人的心意，让人无所适从。唉！《千金方》和《外台秘要》尚且如此，何况后世那些偏颇驳杂混乱的书籍，怎能不迷惑人的心志呢？更等而下之的，还有那些毫无根据、凭空杜撰的邪书，更不值得提起了。
The medical learning of Zhang Zhongjing underwent a significant transformation by the Tang Dynasty. In treating diseases, Zhang Zhongjing’s discussions on Zang-Fu organs (internal organs) and Jing-Luo meridians (meridian system), as well as the transmission and progression of conditions, were entirely based on the *Huangdi Neijing* (Yellow Emperor's Inner Canon). The formulas he used were all classical prescriptions (Jingfang) passed down from ancient sages, not created arbitrarily by personal whim; even when modifications were made, they were necessarily grounded in established principles. The dosages and weights of the herbs strictly adhered to specific standards. Every herb used was derived from the *Shennong Bencao Jing* (Divine Farmer's Materia Medica), with no herb being used loosely or ambiguously. No formula could treat a specific disease other than its designated one, and no prescription could be formed without its specific herbs. Their subtlety and profound sophistication are beyond imagination. With merely five or six ingredients, their therapeutic effects were comprehensive. This reflects the transformative mechanism of Heaven and Earth, and the miraculous application of the sages, which is in harmony with nature and immortal.
The *Qianjin Fang* (Prescriptions Worth a Thousand Gold) is different. Although its discussion of diseases is not devoid of references to the *Huangdi Neijing*, it inevitably incorporates speculative theories from later generations. The formulas it employs are selected from ancient prescriptions but also include methods from later periods that are biased or eclectic. The herbs used are not solely based on the *Shennong Bencao Jing*; they also incorporate miscellaneous single prescriptions and general-purpose remedies. Consequently, there are instances where multiple formulas are established for a single disease, or one formula treats multiple diseases. Some prescriptions contain dozens of ingredients; while many are symptomatic, many others are not, resulting in variable efficacy—some treatments work, others do not. Generally, the emphasis lies heavily on the quantity of herbs, while the ancient sages' methodology for formulating prescriptions has been lost. This constitutes a major shift in the medical way. Nevertheless, its unique use of herbs and ingenious intent establish it as a distinct school with enduring value.
Wang Tao’s compilation in the Tang Dynasty, the *Waitai Miyao* (Essential Prescriptions from the Imperial Library), collected and compiled various prescriptions from the Han Dynasty onwards into a single volume, thereby preserving the prescriptions of successive dynasties comprehensively. However, Wang Tao was not a specialist in medical expertise; thus, he did not exercise rigorous selection to establish a clear guiding principle, making this work essentially a classified collection of medical formulas. Yet, because prescriptions prior to the Tang Dynasty were preserved through this book, its merits cannot be ignored. However, readers who lack a solid foundational understanding ("bamboo in mind") will find themselves confused by the conflicting theories and mixed prescriptions, losing their reference point. Therefore, those studying the *Qianjin Fang* and *Waitai Miyao* must first master the *Huangdi Neijing*, the works of Zhang Zhongjing, and the *Shennong Bencao Jing*. Only by having a firm preconception can one select the strengths and discard the weaknesses, thereby benefiting from their breadth and depth. Otherwise, one’s mind will be confused, leaving one at a loss. Alas! If the *Qianjin Fang* and *Waitai Miyao* are like this, how much more so are the biased, contradictory, and chaotic books of later generations, which inevitably bewilder the mind? Even worse are the baseless, fabricated heretical texts of lower quality, which are hardly worth mentioning.