春温、夏热、秋凉、冬寒，时之正也，而风实应之。凡治感冒，取用表散，自宜随时制方；若应热反凉，病随时变，
施治尤贵圆通。至久晴久雨，燥湿异宜，临症更宜留心，不可概执常例。
凡外感病，挟食者颇多，当思食为邪裹，散其邪则食自下，若杂消导于发散中，不专达表，胃汁复伤，因而陷闭者
有之。至若风多挟暑、湿、寒，或挟燥、火，或恼怒，或劳倦，或房事，及肝气、宿瘕、诸血症，皆外感病之不无有挟
者，所贵随症制宜，斟酌尽善，庶无差误也。
凡内伤病，损上、损下、损及中州，在气、在血、在腑、在脏，用药补救，宜专任，宜的对，无论已，设或挟有外
感，最当留心，补腻即不可施，当以轻剂调停，庶不致粗疏误事。其有上损宜治下，下损宜治上，或砥柱中流，或作隔
二、隔三之治，古人具有良法可师，不敢多赘。
病变无常，方难执一，然无定之中，自有一定之法，此即中无定体，随时而在之道也。盖离规矩不可以为方圆，执
规矩亦不可以为方圆。每见前人用古，师其意而不泥其方，或采取其二三，或减增其一二，得心应手，方推能事。
君、臣、佐、使，制方自有定法，然品味不可拘泥，陆清献曾论仁、义、礼、智、信，随时迭相为用，比之医家之
于君、臣、佐、使也。有然即如参、苓、术、草四君子，随症从宜，因时取用，当亦如十二律之旋相为宫也。
寒、热、温、凉，有一定之药，无一定之治。入腑、入脏，或补、或攻，其气味与性，不可不细按也。故有正用，
亦有反用，有独用，又有兼用，并有活用、借用之不同。如用寒可以治热，反用可以入寒，独用寒而热可除，兼用寒而
热可制，微行消导，大可和中，稍借清滋，自能表汗，隅反焉而取资无尽矣。
外感、内伤，为证治两大关键，然去其所本无，复其所固有，两言可尽之也。盖六淫外袭，身中气血，日失和平，
一切外感有余之症，有须汗、吐、下、和之治，皆是去其所本无也。若七情受伤，腑脏有损，身中气血，日就亏耗，一
切内伤不足之症，有须滋填培补之治，皆是复其所固有也。
读古人书，须识其补偏救弊，一片苦心，互相抵触，即是互相阐发处，所贵多读多看，融会贯通，由博反约，以求
理明心得，临症无望洋之苦是已。若好为指摘，弃瑜录瑕，殊失钦承前哲之道。至矜家秘而执成法，头痛医头，寻方觅
药，一切无方之书置之高阁，此又孟浪之流，不足与语斯道者矣。
Spring warmth, summer heat, autumn coolness, and winter cold are the normal climatic features of the seasons, while Wind pathogen actually corresponds to them. Whenever treating common cold (exogenous diseases), adopting the method of releasing the exterior and dispersing pathogens is appropriate; naturally, one should formulate prescriptions according to seasonal changes. If heat-clearing methods are required but cold-cooling agents are used instead, the disease will change with the season. In such cases, treatment requires particular flexibility and adaptability. Regarding prolonged sunny or rainy weather, where dryness and dampness differ in their suitability for treatment, clinicians must pay close attention during diagnosis and cannot rigidly adhere to conventional examples.
In exogenous diseases, complications involving food stagnation are quite common. One should consider that food is wrapped by pathogens; once the pathogens are dispersed, the food stagnation will naturally descend. If digestive-promoting herbs are mixed into dispersing formulas, failing to focus on reaching the exterior, it may further damage stomach fluids, leading to situations where pathogens sink inward and become closed off. Furthermore, Wind often complicates with Summerheat, Dampness, Cold, or Dryness, Fire. It may also be complicated by anger, fatigue, sexual excess, Liver Qi stagnation, existing abdominal masses (accumulations), or various blood disorders. These are all factors that may complicate exogenous diseases. The value lies in adapting treatment to specific symptoms and deliberating thoroughly to avoid errors.
For endogenous injuries, damage may affect the upper, lower, or middle Jiao (specifically the Spleen and Stomach); it may involve Qi, Blood, Fu organs, or Zang organs. When using medication to remedy these conditions, one should employ dedicated and precise treatments. This is self-evident. However, if an exogenous complication arises, utmost care is needed. Cloying and tonifying herbs must not be used immediately; rather, light and harmonizing agents should be employed to prevent negligence from causing harm. Cases where upper deficiency is treated by addressing the lower, or lower deficiency by addressing the upper, or those employing a "central pillar" approach, or "indirect treatment of two or three steps" (treating related organs to influence the diseased one), have excellent methods established by ancient masters for study. I shall not elaborate further here.
Disease manifestations are unpredictable, and formulas cannot be rigidly applied. Yet, within this unpredictability, there is a certain logic. This is the principle that TCM theory has no fixed form but exists dynamically with time. Generally speaking, without rules and compasses, one cannot draw squares and circles; yet, merely holding onto rules and compasses does not guarantee drawing squares and circles either. It is often seen that predecessors who used ancient formulas learned their intent without being bound by the original prescriptions. They might adopt two or three ingredients, or add/subtract one or two, achieving ease and proficiency, thereby demonstrating the true efficacy of formula construction. The roles of Sovereign (Jun), Minister (Chen), Assistant (Zuo), and Envoy (Shi) in formula preparation have fixed principles, but the selection of herbs should not be dogmatic. Lu Qingxian once discussed Ren (Benevolence), Yi (Righteousness), Li (Propriety), Zhi (Wisdom), and Xin (Trustworthiness), stating they alternate in use according to circumstances, analogous to the Sovereign, Minister, Assistant, and Envoy roles in medicine. Indeed, for example, Si Jun Zi Tang (Four Gentlemen Decoction), composed of Renshen (Ginseng Radix), Fuling (Poria), Baizhu (Atractylodis Rhizoma), and Gancao (Licorice Root), can be adapted to symptoms and seasons, much like the twelve pitch pipes rotating to serve as the Gong tone.
Cold, Heat, Warmth, and Coolness refer to drugs with fixed properties, but treatments lack fixed patterns. Whether entering Fu or Zang organs, or employing tonification or purgation, the flavor and nature of herbs must be carefully analyzed. Thus, there are direct uses and reverse uses; exclusive uses and combined uses; as well as flexible and borrowed uses. For instance, cold herbs can treat heat; reverse use of cold herbs can enter cold syndromes; exclusive use of cold herbs eliminates heat; combined use of cold herbs controls heat. Mild application of digestive methods greatly harmonizes the Middle Jiao; slight borrowing of clearing and moistening methods naturally induces sweating. By inferring from one corner, resources are inexhaustible.
Exogenous and endogenous diseases are the two key aspects of syndrome differentiation and treatment. However, removing what was originally absent and restoring what was originally inherent can summarize them in two words. Generally, when Six Excesses (Wind, Cold, Summerheat, Dampness, Dryness, Fire) attack externally, the body's Qi and Blood lose harmony daily. All exogenous excess syndromes requiring Sweating, Vomiting, Purging, or Harmonizing treatments aim to remove what was originally absent. Conversely, if Seven Emotions cause injury and Zang-Fu organs are damaged, the body's Qi and Blood decline daily. All endogenous deficiency syndromes requiring nourishing, filling, and tonifying treatments aim to restore what was originally inherent.
When reading ancient texts, one must recognize the sincere effort behind correcting biases and saving deficiencies. Apparent contradictions are often points of mutual elaboration. The value lies in extensive reading and observation, integrating knowledge comprehensively, moving from broad to concise, seeking clear understanding and personal insight, so that clinical practice avoids the distress of facing vast medical literature without direction. To merely criticize and pick flaws, discarding excellence for mediocrity, is to fail in respecting previous sages. As for boasting about family secrets, adhering rigidly to established methods, treating only the head when the head hurts, seeking specific prescriptions and herbs, and shelving books that do not prescribe fixed formulas, these are the actions of rash and superficial individuals, unworthy of discussing the Great Way of Medicine.