1. The Six Evils

1. The Six Evils

These are wind, cold, summer heat, dampness, dryness, and fire. They are originally six types of climatic changes in nature, normally called the Six Qi. When these natural phenomena exceed the body's ability to adapt—sometimes too much, sometimes too little—they become pathogenic factors. In TCM, the Six Evils refer specifically to situations where the Six Qi are either excessive or insufficient. "Evil" here means "excess" or "insufficiency."

(1) Wind

Wind is the "chief of all diseases," meaning it can combine with any pathogenic factor to cause illness together. Examples include wind-cold, wind-damp, and wind-heat. Wind is highly mobile and ever-changing, often leading to sudden and severe conditions such as heat generating wind or internal liver wind. Additionally, wind-damp can migrate and cause pain in unpredictable locations. Wind belongs to the Wood element, is flexible and open, and primarily governs dispersal; treatment for wind-related illnesses mainly focuses on dispersing and releasing.

(2) Cold

Cold has a contracting effect, and when contraction occurs, blockage follows, leading to pain. Most pain syndromes respond well to warming and dispersing therapies. Cold easily harms yang, and wherever cold resides, yang energy will inevitably be deficient. Therefore, most herbs used to dispel cold have yang-tonifying properties.

(3) Summer Heat

Summer heat is intensely hot and depletes qi while damaging body fluids. This means summer heat carries both fiery and drying qualities, capable of harming yin and exhausting qi. Summer heat is often accompanied by dampness, resulting in gastrointestinal symptoms like vomiting and diarrhea. Moreover, summer heat illnesses occur in environments unique to summer, hence the term "summer heat."

(4) Dampness

Dampness is heavy and tends to descend, with the lower burner often being the primary site of dampness in clinical practice. Dampness is sticky and difficult to eliminate quickly; any condition involving dampness tends to be prolonged. For example, wind-cold and wind-heat may resolve within days, but wind-damp can linger for a long time. Similarly, ascites, pleural effusion, and joint effusion are all examples of dampness-related conditions, characterized by long durations. Heavy dampness can obstruct the flow of qi, and when qi flow is blocked, pain ensues. Therefore, most pain-relieving medicines also have dampness-dispelling effects.

(5) Dryness

Dryness is prevalent in autumn, hence the term "autumn dryness." Dryness manifests as "three drynesses" (dry throat, dry nose, dry mouth). Dryness is a yang evil and easily damages body fluids.

(6) Fire

Fire ascending upward is an important concept in TCM regarding fire-related conditions. When fire arises in the lower burner, it often combines with dampness to cause illness; otherwise, it cannot cause disease. Hence the saying "there is no pure fire in the lower burner." Fire easily harms yin. Any formula that clears fire should be paired with yin-nourishing herbs to enhance its effectiveness—for example, the rhizome of Anemarrhena in Baihu Tang, the Rehmannia root in Longdan Xiegan Tang, and the Cortex Lycii in Xiebai San. Fire can also force blood to flow erratically, with more than half of bleeding cases caused by fire. Clearing fire can stop bleeding, with Sanhuang Xiexin Tang being a representative formula.

2. The Seven Emotions

Joy, anger, worry, contemplation, sadness, fear, and fright are collectively known as the Seven Emotions. These are normal mental activities and usually do not cause disease. However, if these seven emotional states result from prolonged or sudden psychological stimulation that exceeds the body's normal adaptive capacity, they become pathogenic factors that disrupt organ function, disturb qi and blood circulation, and upset the balance of yin and yang, ultimately leading to illness.

• Joy Excessive joy harms the heart and disperses qi.
• Anger Extreme anger harms the liver and causes qi to reverse.
• Worry Chronic worry harms the lungs and leads to qi stagnation.
• Contemplation Excessive contemplation harms the spleen and causes qi to stagnate.
• Sadness Sadness harms both the heart and lungs and causes qi to condense.
• Fear Fear harms the kidneys and leads to qi deficiency.
• Fright Fright injures the heart, kidneys, liver, and gallbladder, and causes qi to become chaotic.

The basic concept of etiology in TCM revolves around the Six Evils and the Seven Emotions, with the former representing external causes and the latter internal causes. Together, these internal and external factors form the main framework for etiological differentiation in traditional Chinese medicine. In addition, there are also factors such as improper sexual conduct, dietary and labor overexertion, and injuries from insects, beasts, or metal weapons, collectively referred to as "neither internal nor external causes," which play only a secondary role in etiological differentiation. In recent years, some scholars have proposed new pathogenic factors such as air pollution, chemical toxins, and radioactive dust, which deserve further study and are of great significance in enriching and developing the theory of etiology in TCM.

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Section 6: The Internal Medicine Formulary System of Traditional Chinese Medicine

The internal medicine formulary system is the mainstream of TCM prescriptions. By "internal medicine prescriptions," we generally mean all oral herbal decoctions. These decoctions serve as the primary method for treating internal diseases, having been refined over thousands of years to form the core framework of TCM internal medicine therapy. At the same time, they also play an extremely important role in treating non-internally related diseases, fully embodying the holistic view of TCM that treats external diseases internally, internal diseases externally, upper diseases lower, and lower diseases upper—viewing the entire body as a single, integrated system. The internal medicine formulary system can broadly be divided into six major systems: the Ephedra-Cinnamon Twig system, the Bupleurum system, the White Tiger-Chengqi system, the Four Gentlemen-Four Substances system, the Six Flavor Rehmannia system, and the Mulberry-Chrysanthemum-Yinqiao system.

I. The Ephedra-Cinnamon Twig System

All formulas in this system originate from the "Shanghan Lun" and "Jingui Yaolue." The main formulas, Ephedra Decoction and Cinnamon Twig Decoction, were originally the primary treatments for exogenous wind-cold, but through various modifications and adaptations, they have evolved into a vast system of prescriptions. Not only are they effective for treating exogenous diseases, but they also demonstrate remarkable efficacy in treating a wide range of internal ailments.