太阳病，发热而渴为温病，是少阴伏邪、出于太阳，以其热从内发，故渴而不恶寒。若外感温病，初起却有微恶寒
者，以风邪在表也；亦不渴，以内无热也；似伤寒而实非伤寒，如辨别不清，多致误治。
冬月伤寒，邪由皮毛而入，从表入里。初见三阳经证，如太阳病，则头项强痛而恶寒之类。三阳不解，渐次传入三
阴。其中有留于三阳而不入三阴者；有结于胃腑而不涉他经者；亦有不必假道三阳而直中三阴者。凡此伤寒之证，初起
悉系寒邪见象。迨发作之后，渐次化热内传，始有热象。故初起治法，必以通阳祛寒为主。及化热之后，始有泄热之法。
此伤寒病之大较也。若夫温病，乃冬时寒邪伏于少阴，迨春夏阳气内动，伏邪化而为热，由少阴而外出，如邪出太阳，
亦见太阳经证，其头项强痛等象，亦与伤寒同。但伤寒里无郁热，故恶寒不渴，溲清无内热；温邪则标见于外，而热郁
于内，虽外有表证，而里热先盛，口渴溲黄，尺肤热，骨节疼，种种内热之象，皆非伤寒所有。其见阳明、少阳，见症
亦然。初起治法，即以清泄里热，导邪外达为主，与伤寒用药一温一凉，恰为对待。盖感寒随时即发，则为伤寒，其病
由表而渐传入里；寒邪郁久化热而发，则为温病，其病由里而郁蒸外达。伤寒初起，决无里热见证；温邪初起，无不见
里热之证。此伤寒温病分证用药之大关键，临证时能从此推想，自然头头是道矣。
太阳病中，出现发热且口渴症状的，属于温病。这是少阴经潜伏的病邪，发于太阳经，因为热邪从体内发出，所以表现为口渴而不恶寒。如果是外感引起的温病，初起时却有轻微恶寒的症状，这是因为风邪在体表；同时也不口渴，因为体内没有热邪；这种情况看似伤寒但实际上不是伤寒，如果辨别不清楚，很容易导致误治。
冬季感受寒邪而患伤寒，病邪从皮毛侵入，由表入里。初期可见三阳经的证候，如太阳病，就会出现头项强痛且恶寒等症状。如果三阳经的病证未解，病邪会渐渐传入三阴经。其中有的病邪停留在三阳经而不进入三阴经；有的结聚在胃腑而不涉及其他经络；也有不需要经过三阳经而直接侵犯三阴经的情况。所有这些伤寒的证候，初起都表现为寒邪的特征。等到发作之后，病邪渐渐化热并内传，才出现热象。因此，初起的治疗原则，必须以通阳散寒为主。等到化热之后，才有清热泄火的治疗方法。这是伤寒病的大致情况。至于温病，是冬季寒邪潜伏在少阴经，等到春夏季节阳气在内涌动，潜伏的病邪化为热邪，从少阴经向外发散，如果邪气出于太阳经，也会出现太阳经的证候，其头项强痛等表现，也与伤寒相同。但是伤寒体内没有郁积的热邪，所以恶寒不口渴，小便清长且无内热；温邪则标症见于外部，而热邪郁积在内部，虽然外部有表证，但内部热势先盛，表现为口渴、小便黄赤、尺部皮肤发热、骨节疼痛，种种内热的征象，都不是伤寒所具有的。见到阳明经或少阳经的证候，情况也是如此。初起治疗时，即以清泄里热、引导邪气向外透达为主要方法，与伤寒用药一温一凉，恰好相对立。大概感受寒邪随即发病的，就是伤寒，其病情由表逐渐传入里；寒邪郁积日久化热而后发病的，就是温病，其病情由里向外郁蒸发散。伤寒初起，绝对没有里热的见证；温邪初起，无不伴有里热的证候。这是区分伤寒和温病进行辨证用药的关键所在，临证时若能由此推想，自然就能条理清晰了。
In Taiyang disease (Taiyang disease, a syndrome caused by pathogenic factors affecting the Taiyang meridian), fever accompanied by thirst indicates Warm Disease (Warm Disease, an exogenous febrile disease caused by warm pathogens). This is latent pathogenic qi in Shaoyin (Shaoyin, referring to the Kidney and Heart meridians) emerging from Taiyang. Because the heat originates from within, it manifests as thirst without aversion to cold. If it is a Warm Disease contracted externally, there may be slight aversion to cold at the onset due to Wind pathogen remaining in the exterior; there is also no thirst because there is no internal heat. It resembles Cold Damage (Cold Damage, diseases caused by cold pathogens) but is not actually Cold Damage. If differentiation is unclear, misdiagnosis and mistreatment often occur.
In winter, Cold Damage occurs when pathogenic factors enter through the skin and hair, moving from the exterior to the interior. Initially, symptoms of the Three Yang meridians appear, such as in Taiyang disease, where stiffness and pain in the head and neck with aversion to cold are seen. If the Three Yang conditions do not resolve, the pathogen gradually transmits into the Three Yin meridians. Some pathogens remain in the Three Yang without entering the Three Yin; some knot in the Stomach Fu organ without involving other meridians; and some directly strike the Three Yin without passing through the Three Yang. All these Cold Damage syndromes initially present with signs of Cold pathogen. Only after onset does the pathogen gradually transform into heat and transmit inward, presenting heat signs. Therefore, initial treatment must focus on unblocking Yang and dispelling Cold. Only after transformation into heat are methods for draining heat applied. This is the general principle of Cold Damage.
As for Warm Disease, it results from Cold pathogen latent in Shaoyin during winter. When Yang Qi moves internally in spring and summer, the latent pathogen transforms into heat and exits from Shaoyin outward. If the pathogen exits via Taiyang, Taiyang meridian symptoms appear, including stiffness and pain in the head and neck, similar to Cold Damage. However, Cold Damage lacks internal stagnant heat, so there is aversion to cold without thirst, clear urine, and no internal heat. In contrast, Warm pathogen shows external manifestations while heat stagnates internally. Although external exterior symptoms exist, internal heat is vigorous first, manifesting as thirst, yellow urine, heat in the Chi pulse area (Chi position, the deepest part of the radial pulse), bone and joint pain, and various other internal heat signs, none of which are found in Cold Damage. The same applies to symptoms appearing in Yangming (Yangming, referring to the Large Intestine and Stomach meridians) or Shaoyang (Shaoyang, referring to the Gallbladder and Sanjiao meridians). Initial treatment focuses on clearing and draining internal heat and guiding the pathogen outward. The medication contrasts sharply with that for Cold Damage: one is warming, the other cooling. Generally, Cold pathogen causing immediate illness is Cold Damage, progressing from exterior to interior; Cold pathogen lingering and transforming into heat before erupting is Warm Disease, progressing from interior outward through steaming and dispersal. Cold Damage never presents with internal heat signs at onset; Warm Disease always presents with internal heat signs at onset. This is the critical key to differentiating and prescribing for Cold Damage versus Warm Disease. Clinical application based on this reasoning will naturally be logical and precise.