The therapeutic principles of Traditional Chinese Medicine (TCM) are generalized theories—gradually distilled from long-term clinical practice based on an understanding of the universal laws governing the onset and progression of disease—that directly guide the formulation of specific treatment methods and the selection of herbal formulas. These principles are inextricably linked to the process of syndrome differentiation.

I. Strengthening *Zheng* (Upright Qi) and Eliminating *Xie* (Pathogenic Factors)

The course of any disease is essentially a struggle between two opposing forces: *Zheng* (Upright Qi, the body's vital energy and resistance) and *Xie* (Pathogenic Factors, the causes of disease). Therefore, the fundamental goal of treatment is to alter the balance of power between these two forces, thereby eliminating the pathogen, restoring the body's vital energy, and steering the disease toward recovery. In clinical practice, this objective is achieved primarily through the strategies of "eliminating pathogenic factors" and "strengthening Upright Qi." 

"Strengthening Upright Qi" involves the use of medicinal agents to bolster the body's vital energy and enhance its disease-fighting capacity, ultimately overcoming the illness. This approach—often termed "strengthening Upright Qi to eliminate pathogenic factors"—is indicated for conditions characterized by a deficiency of Upright Qi; specific therapeutic methods include supplementing Qi, nourishing blood, enriching *Yin*, and tonifying *Yang*. "Eliminating pathogenic factors" (quxie) refers to the use of medicinal agents that expel pathogens to achieve the goal of removing the disease-causing influence and restoring the body's healthy energy (*zhengqi*). This approach—often termed "eliminating pathogens to support healthy energy"—is applicable to conditions where the pathogenic factor is strong but the body's healthy energy is not yet depleted; therapeutic methods include inducing sweating, clearing heat, purging, and promoting diuresis.

During the course of an illness, the struggle between healthy energy and pathogenic factors involves constantly shifting dynamics; therefore, the methods of supporting healthy energy and eliminating pathogens must be applied flexibly and combined based on syndrome differentiation. Strategies may include attacking first and tonifying later, tonifying first and attacking later, or employing both attacking and tonifying measures simultaneously.

II. Standard Treatment (*Zhengzhi*) and Contrary Treatment (*Fanzhi*)

Standard treatment involves using medicinal agents with properties opposite to the nature of the disease. For example, cold syndromes are treated with warming agents; heat syndromes with cooling agents; excess syndromes with purging agents; and deficiency syndromes with tonifying agents. Contrary treatment is the exact opposite of standard treatment—hence the name "contrary treatment"—meaning the properties of the medication align with the apparent manifestations (or "false signs") of the disease. Examples include using warming agents despite the presence of heat signs, or cooling agents despite the presence of cold signs. In essence, however, the treatment still targets the underlying nature of the disease; the "contrary" nature is merely superficial. Consider a case of excess heat syndrome where intense internal heat repels *yin* outward, preventing *yang* energy from reaching the extremities and resulting in cold limbs (a condition known as "true heat with false cold"). In this instance, cooling agents are used rather than warming ones—a practice known as "using cold to treat cold."

III. Treating the Same Disease Differently and Treating Different Diseases Similarly In the application of Traditional Chinese Medicine's principle of syndrome differentiation and treatment, two fundamental concepts must be observed: treating the same disease differently and treating different diseases with the same method. "Treating the same disease differently" applies when the same disease arises from different causes, or when the same disease manifests different characteristics at different stages, requiring distinct treatment approaches. "Treating different diseases with the same method" applies when different diseases share the same underlying cause, or when different diseases—during their progression—reach a stage characterized by the same nature, thereby calling for the same treatment strategy.