尝谓气色之于症候也。有有定者。有无定者。主病条目。有定之言也。诊法提纲。无定之论也。知主病之有
定。而不通乎法。其失也胶。知诊法之无定。而不究其病。其失也泛。且主病之言虽有定。而合之于法则无
定。诊法之论虽无定。而合之于病则有定。病同者。其法同。病异者。其法异。法者有物有则。无体无方。有定
而无定。无定而有定者也。是故以千变万化之法。察千变万化之病。病无定。法亦无定。以千变万化之法。
察千变万化之证。证有定。法亦有定。夫千变万化之病。形于外者。固有无定之证。而千变万化之证。由于
中者。实有有定之义。故以病为有定。而病则因人而无定。以病为无定。而病则因证而有定。证也者。病之
着于形色。发于声音。显于症候。应于脉息者也。证定焉。法斯定矣。后之学人。勿执有定之条目。以测无定
之病情。当知无定之病情。必见有定之气色。斯有病即有证。有证即有定矣。由是化而裁之。推而行之。则
夫主病之条目。增之可也。删之可也。因而损益之。亦无不可也。虽然。病之有色。病之已形者也。色之有象。
色之已见者也。已形已见者。可以言定。未形未见者。不可以言定。况有已定而难于形容。未定而难于拟
议者。是以提纲易详。而条目难尽也。高明之家。读书而精究其意义。临症而熟察其情形。其所得于观感
之间。语言之外者。抑又深于此矣。神而明之。存乎其人。
余着是书。上卷推而言之。故不厌其详。下卷约而言之。故不嫌其简。然详者当约之以求简。简者当
推之以求详。若读一句只一句。读一篇只一篇。则详者近穿凿。简者近缺略矣。其自五官以下。条目
亦从简者。盖提纲已挈其要领。而条目之见于古书者。皆医所必读。医所必阅。缺之于此。欲其求之
于彼也。至若所引圣经贤传。或断章取义。或互文见意。以为辞不颠倒。则义有不显。理不合参。则意
有不达。原欲人因是明经。非欲人以是荒经。譬之作文题目。拆开意义自见。不比注解经传。句不可
移。字不可减。且经传具在。或不以是为罪乎。
我曾说过，气色与症候之间，既有固定不变的规律，也有灵活变化的情况。主病条目中记载的是固定不变的法则，而诊法提纲阐述的则是灵活变化的理论。如果只知道主病有固定规律，却不通晓诊法的灵活运用，其弊端在于拘泥固执；如果只知道诊法灵活多变，却不深入探究具体病情，其弊端在于空泛不切实际。况且，主病的言论虽然看似固定，但结合诊法来看又是灵活的；诊法的论述虽然看似灵活，但结合具体病情来看又是固定的。病情相同，则诊法相同；病情不同，则诊法不同。诊法既有实质内容又有规范准则，但没有固定的形体和死板的方法，它是固定与灵活统一的辩证关系。因此，用千变万化的诊法来观察千变万化的病情，病情没有固定模式，诊法也就没有固定模式；用千变万化的诊法来察验千变万化的证候，证候有确定的表现，诊法也就有了确定的依据。那些千变万化的病情，表现在外部的确存在没有固定模式的证候，而那些千变万化的证候，源于体内脏腑气血的变化，实际上有着确定的内在含义。所以，如果说病情是固定的，那么病情就会因为个体差异而没有固定模式；如果说病情是不固定的，那么病情就会因为证候的表现而有确定依据。所谓“证”，就是病情在面色形态上的显现、在声音中的流露、在症候中的展示以及在脉象呼吸中的反应。证候确定了，诊法也就确定了。后世的学医者，不要执着于固定的条目去推测多变的病情，应当明白多变的病情必然呈现出具有规律性的气色特征。这样就能做到有病就有证，有证就有定论。由此加以变化裁断，推广施行，那么对于主病的条目，增加是可以的，删减也是可以的，根据情况进行增减损益，也没有不可以的。
虽然如此，病情表现为气色，是病情已经形成的状态；气色呈现形象，是气色已经被观察到的状态。已经形成和被观察到的，可以说是有固定规律的；尚未形成和未被观察到的，不可以说有固定规律。更何况有的已经确定却难以形容，有的尚未确定却难以揣测。因此，提纲容易详尽，而条目难以穷尽。高明的人家，读书时精研其意义，临症时熟察其情形，他们所获得的在观察感悟之间、言语之外的深刻体会，又比文字记载更为深远。神妙地领悟它，关键在于个人的修养与悟性。
我撰写这本书，上卷推演阐述，所以不厌其烦地详尽；下卷概括总结，所以不嫌其简略。然而，详尽的内容应当简约以求精炼，简略的内容应当推演以求详实。如果读一句只理解一句，读一篇只理解一篇，那么详尽的内容就近乎穿凿附会，简略的内容就近乎缺失遗漏。其中关于五官以下的条目也采取简略写法，是因为提纲已经抓住了要领，而条目中见于古书的内容，都是医生必须阅读、必须了解的。如果在这里省略了，想要在其他地方找到就难了。至于所引用的经典著作，有时断章取义，有时互文见意，是为了使辞句不颠倒，否则意义就不显豁；道理如果不参合比较，意思就不能通达。原本是想让人通过这些内容来明晓经义，并不是想让人因为这些内容而荒废对经典的研读。这就像作文的题目，拆开来看意义自然显现，不像注解经传那样，句子不能移动，字数不能减少。而且经典原文都在那里，或许不会因此怪罪我吧。
I have often said that the relationship between Qi and color (Qi Se, 气色: the luster and hue of the skin/face reflecting internal health) and symptoms is characterized by both fixed principles and flexible variations. The entries for primary diseases (Zhu Bing, 主病: specific disease manifestations) state the fixed rules, while the outline of diagnostic methods (Zhen Fa Ti Gang, 诊法提纲: general guidelines for diagnosis) discusses the flexible theories. If one knows only that primary diseases have fixed patterns but fails to understand the flexibility of diagnostic methods, the error lies in being rigid and dogmatic. If one knows only that diagnostic methods are flexible but fails to investigate the specific pathology, the error lies in being vague and superficial. Furthermore, although the statements regarding primary diseases appear fixed, they become flexible when applied through diagnostic methods; although the discussions on diagnostic methods appear flexible, they become fixed when applied to specific diseases. When the disease is the same, the method is the same; when the disease differs, the method differs. Diagnostic methods possess substance and principles, yet lack a fixed form or rigid formula; they are simultaneously fixed and flexible. Therefore, using infinitely variable diagnostic methods to observe infinitely variable diseases, if the disease has no fixed pattern, the method also has no fixed pattern. Using infinitely variable diagnostic methods to examine infinitely variable syndromes (Zheng, 证: syndrome patterns), since the syndromes have definite manifestations, the methods also have definite bases. Those infinitely variable diseases manifest externally as syndromes that may indeed lack fixed patterns, yet those infinitely variable syndromes, originating from internal factors, actually possess definite intrinsic meanings. Thus, if one considers the disease as fixed, it becomes non-fixed due to individual differences; if one considers the disease as non-fixed, it becomes fixed due to the manifestation of syndromes. A "syndrome" (Zheng, 证) is the disease manifested in facial features and complexion, emitted in voice, displayed in symptoms, and responded to in pulse and respiration. Once the syndrome is determined, the method is determined. Future students should not cling to fixed entries to speculate on variable disease conditions; rather, they should understand that variable disease conditions inevitably reveal regularized Qi and color patterns. In this way, where there is disease, there is a syndrome; where there is a syndrome, there is certainty. From this, one can adapt and apply these principles, making additions or deletions to the entries for primary diseases as appropriate, or modifying them according to circumstances.
Although so, disease presenting with color indicates that the disease has taken form; color presenting with imagery indicates that the color has been observed. What has taken form and been observed can be described as having fixed rules; what has not yet taken form or been observed cannot be described as fixed. Moreover, some things are already determined yet difficult to describe, while others are undetermined yet difficult to conjecture. Hence, outlines are easier to detail comprehensively, whereas entries are harder to exhaust completely. Wise practitioners, upon studying texts, carefully investigate their meanings; upon clinical practice, they closely observe situations. Their insights gained through observation and intuition, beyond mere language, are profound. Divine understanding depends on the individual.
In writing this book, the upper volume expands upon the subject, thus avoiding excessive detail; the lower volume summarizes concisely, thus avoiding unnecessary brevity. However, detailed content should be condensed to seek simplicity, and simple content should be expanded to seek detail. If one reads one sentence and understands only that sentence, or reads one chapter and understands only that chapter, then detailed content approaches forced interpretation, and simple content approaches omission. The entries below the five sense organs are also kept concise because the outline has already grasped the essentials, and the entries found in ancient texts are essential reading for physicians. If omitted here, seeking them elsewhere would be difficult. As for the cited classics, sometimes meaning is extracted out of context, or mutual textual references are used to clarify intent, ensuring that the phrasing is not inverted, otherwise the meaning would not be clear. If principles are not cross-referenced, the intent cannot be fully understood. The original intention was to help people understand the classics through these examples, not to cause them to neglect the classics. It is like an essay topic: when broken down, the meaning reveals itself naturally, unlike annotating classics where sentences cannot be moved and characters cannot be removed. Since the classics remain intact, perhaps I will not be blamed for this approach.