新感温热，邪从上受，必先由气分陷入血分，里症皆表症侵入于内也。伏气温热，邪从里发，必先由血分转出气分，
表症皆里症浮越于外也。新感轻而易治，伏气重而难疗，此其大要也。
谓予不信，请述陆氏九芝评孟英之言曰∶仲景所论温热，是伏气。天士所论温热，是外感，故以温邪上受、首先犯
肺、逆传心包十二字，揭之篇首，以自别异。果如其说，则所称温热者，即俗所谓小风温、小风热，如目赤、颐肿、喉
梗、牙疼之类，却只须辛凉轻剂，其病立愈。更述薛瘦吟之言曰∶凡病内无伏气，纵感风寒暑湿之邪，病必不重，重病
皆新邪引发伏邪者也。但伏气有二∶伤寒伏气，即春温夏热病也；伤暑伏气，即秋温冬温病也。邪伏既久，血气必伤，
故治法与伤寒伤暑正法大异。且其气血亦钝而不灵，故灵其气机，清其血热，为治伏邪第一要义。第其间所伏之邪，有
微甚，有浅深；人之性质，有阴阳，有强弱，故其中又有轻重之分焉。医必识得伏气，方不至见病治病，能握机于病象
之先。然非熟于亢害承制之理，亦岂能测未来之病乎？然非谓司天运气也，雨 寒燠，在在留心，久当自悟耳。
由是观之，同一温热症，而新感之与伏气，病所之浅深不同，病情之轻重不同，病机之安危不同，故其疗法，亦因
之而不同。
新感温热病，邪气从上部侵入，必定先由气分陷入血分，所有的里证都是表证侵入体内所致。伏气温热病，邪气从内部发出，必定先由血分转出气分，所有的表证都是里证浮越于体表所致。新感病情轻浅且容易治疗，伏气病情深重且难以治愈，这是它们的主要区别。
如果你不相信，请听陆九芝评价王孟英的话说：张仲景所论述的温热病，属于伏气；叶天士所论述的温热病，属于外感。因此，叶氏以“温邪上受，首先犯肺，逆传心包”这十二个字作为篇首纲领，以此与张仲景的理论区分开来。如果确实如此，那么所称的温热病，就是民间所谓的小风温、小风热，比如眼睛发红、腮部肿胀、咽喉梗塞、牙痛这类病症，只需要使用辛凉轻剂，病立刻就能痊愈。
再引述薛瘦吟的话说：凡是体内没有伏气的疾病，即使感染了风寒暑湿等邪气，病情一定不重，重病都是由新邪引发伏邪所致。但是伏气有两种：伤寒伏气，即春温和夏热病；伤暑伏气，即秋温和冬温病。邪气潜伏时间既久，气血必然受损，所以治疗方法与伤寒、伤暑的正治法大不相同。而且患者的气血也迟钝而不灵动，因此调畅气机、清除血热，是治疗伏邪的第一要义。只是其中潜伏的邪气，有轻微和严重之分，有浅表和深入之别；人的体质，有阴阳属性，有强弱差异，所以病情又有轻重之分。医生必须识别出伏气，才不会见到病症就只治病症，能够把握先机于病象显现之前。然而，如果不精通亢害承制（五行生克制化中异常制约关系）的道理，又怎能预测未来的疾病呢？但这并不是指司天运气（五运六气学说），而是指对雨、寒、暖等各种气候现象处处留心，时间久了自然会有领悟。
In new-onset warm-heat disease, the pathogenic factor enters from the upper orifices and must first sink from the Qi level (Qi Fen) into the Blood level (Xue Fen); all interior syndromes are exterior syndromes invading inward. In latent warm-heat disease, the pathogenic factor emerges from the interior and must first transition from the Blood level to the Qi level; all exterior syndromes are interior syndromes floating outward to the surface. New-onset cases are mild and easy to treat, whereas latent cases are severe and difficult to cure; this is the general principle.
If you do not believe this, let me quote Lu Jiuzhi's evaluation of Wang Mengying: Zhang Zhongjing discussed warm-heat disease as latent [pathogens], while Ye Tianshi discussed warm-heat disease as external contraction. Therefore, Ye placed the twelve characters "Warm pathogens enter from above, initially attacking the Lung, and may reversely transmit to the Pericardium" at the beginning of his chapter to distinguish his theory. If this is true, then the so-called warm-heat disease refers to what is commonly known as minor wind-warmth or minor wind-heat, such as red eyes, swollen parotids, throat obstruction, and toothache. Such conditions require only mild acrid-cool formulas, and the illness will be cured immediately.
Furthermore, let me cite Xue Shouyin: Whenever there is no latent pathogen within, even if one contracts Wind-Cold, Summer-Heat, or Dampness, the disease will certainly not be severe; severe diseases are always triggered by new pathogens activating latent ones. However, there are two types of latent pathogens: Latent Cold Damage pathogens refer to Spring-Warmth and Summer-Heat diseases; Latent Summer-Heat pathogens refer to Autumn-Warmth and Winter-Warmth diseases. Since the pathogen has been latent for a long time, Qi and Blood must be damaged; thus, treatment methods differ significantly from the standard protocols for Cold Damage and Summer-Heat. Moreover, the patient's Qi and Blood become sluggish and unresponsive. Therefore, regulating Qi mechanism and clearing Heat from the Blood are the primary principles in treating latent pathogens. Nevertheless, the latent pathogen varies in intensity (mild vs. severe) and depth (superficial vs. deep); human constitutions vary in Yin-Yang balance and strength/weakness; hence, there are further distinctions in severity. A physician must recognize latent pathogens to avoid merely treating symptoms as they appear, thereby grasping the opportunity before clinical manifestations arise. However, without mastering the principles of *Kang Hai Cheng Zhi* (the mutual restriction and control among the Five Elements when imbalance occurs), how can one predict future illnesses? This does not refer to the Theory of Si Tian Yun Qi (Five Movements and Six Qi); rather, it implies paying close attention to climatic variations such as rain, cold, and warmth, which will lead to self-realization over time.
From this perspective, although both are warm-heat syndromes, new-onset and latent cases differ in the depth of pathology, the severity of the condition, and the stability of the pathological mechanism; consequently, their therapeutic approaches also differ accordingly.