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The sun, moon, and stars are phenomena in the sky that can be seen; water, fire, earth, and stones are tangible forms on the earth that can be sought; insects and plants are visible entities among animals and flora. The cold, heat, warmth, and coolness of the four seasons represent the cycle of climatic qi (vital energy), which can be perceived. As for mountain mists, miasmas, and toxic fogs in Lingnan, these are all turbid qi generated by the earth, yet they can still be observed. However, the "miscellaneous qi" (Za Qi, 杂气) of heaven and earth is diverse and varied, just as there are sun, moon, and stars in the sky, water, fire, earth, and stones on the ground, and various insects and plants in the realm where qi interacts.

Among plants, there are wild gelsemium (Ye Ge) and croton seeds (Ba Dou); among stars, there are malefic stars like Luo Hou and Ji Du; among insects, there are venomous snakes and fierce beasts; among earth and stones, there are minerals like realgar (Xiong Huang), sulfur (Liu Huang), arsenic trioxide (Pi Shuang), and stibnite (Xin Shi). All things have their good and evil, superior and inferior qualities; thus, we know that the toxicity of miscellaneous qi also varies in severity. Yet this qi cannot be sought through form, nor can it be seen, let alone heard or smelled. How then can it be perceived? How can humans know its existence, or know that it exists in many different forms? This qi arrives without fixed timing and strikes without fixed location. When people come into contact with it, they develop various diseases according to the specific qi they encounter.

These diseases may manifest as simultaneous swelling of the parotid glands (Fa Yi) in a group of people; or simultaneous edema of the head and face, commonly known as "Big Head Plague" (Da Tou Wen); or simultaneous sore throat, sometimes with hoarseness, commonly known as "Toad Plague" (Ha Ma Wen); or simultaneous malaria and dysentery; or bi-syndrome (Bi Qi), smallpox (Dou Chuang), macules and papules (Ban Zhen), sores, scabies, and carbuncles (Ding); or simultaneous red, swollen, and painful eyes; or simultaneous hematemesis and sudden diarrhea, commonly known as "Melon Rind Plague" (Gua Rang Wen) and "Probing Head Plague" (Tou Tou Wen); or simultaneous goiters (Ying), commonly known as "Lump Plague" (Ge Da Wen). The variety of diseases is too numerous to list. Generally, if a disease is confined to a specific region, affecting entire households and groups of people identically, it is due to epidemic qi (Shi Xing Zhi Qi), which is essentially disease caused by miscellaneous qi. The diversity of diseases proves the diversity of the qi.

It is likely that at that time, a specific type of miscellaneous qi specifically entered certain organs and meridians, causing a specific disease, hence the similarity in symptoms among the infected. This confirms the diversity of the qi, rather than implying that the organs and meridians themselves determine the syndrome. Diseases cannot be constrained by years or seasons, as they are not fixed by the Five Movements and Six Qi (Wu Yun Liu Qi). Thus, the arrival of the qi is unpredictable. It may erupt in cities or villages, while other places remain safe, proving that the qi strikes without fixed location. Epidemic qi (Yi Qi) is one type of miscellaneous qi, but it is more potent, hence called "pestilential qi" (Li Qi). Although the number of cases varies, it occurs every year. Diseases like Melon Rind Plague and Lump Plague are the most severe; mild cases may die from morning to evening, and acute cases may die within moments. Fortunately, such cases have been rare for hundreds of years and should not be compared to common epidemics.

Regarding diseases like parotid swelling, sore throat, red eyes, and rashes, even if only one or two individuals in a village are affected at a given time, their symptoms closely match those of the widespread outbreaks in previous years, and the treatment methods are identical. This is the same miscellaneous qi, but currently, the concentration is low, and few are infected. One cannot conclude it is not miscellaneous qi simply because most people are unaffected. Moreover, miscellaneous qi causes the majority of diseases, yet the world mistakenly attributes them to the "Six Qi" (Wind, Cold, Summer-heat, Dampness, Dryness, Fire). For instance, mistaking wind pathogen for conditions like leprosy (Da Ma Feng), knee deformity (He Xi Feng), gout (Tong Feng), migratory joint pain (Li Jie Feng), stroke in the elderly (Zhong Feng), intestinal wind (Chang Feng), leprous wind (Li Feng), and epileptic wind (Xian Feng), and treating them all with wind-dispelling herbs yields no effect, as they are not wind but miscellaneous qi. Mistaking fire pathogen for conditions like carbuncles (Ding Chuang), back abscesses (Fa Bei), ulcers (Yong Ju), swellings (Zhong Du), flowing toxins (Liu Zhu), flowing fire (Liu Huo), erysipelas (Dan Du), and rashes/smallpox, and assuming all painful/itchy sores belong to Heart Fire, and treating them with Scutellaria (Huang Qin), Coptis (Huang Lian), Gardenia (Zhi Zi), and Phellodendron (Huang Bai) yields no effect, as they are not fire but miscellaneous qi. Mistaking summer-heat for cholera (Huo Luan), vomiting, diarrhea, malaria, dysentery, acute diarrhea (Bao Zhu), abdominal pain, and intestinal cramping (Jiao Chang Sha), and treating them as summer-heat syndromes yields no effect, as they have nothing to do with summer-heat.

All miscellaneous disorders arising without obvious cause are formed by miscellaneous qi. Why were they unknown in ancient times? Because when these qis arrive, people do not perceive them; when infected, they feel nothing. People only seek causes in the visible and perceptible Wind, Cold, Summer-heat, and Dampness, ignoring the silent, odorless, invisible, and inaudible qi. Having misidentified the pathogen, they inevitably administer wrong medicines. As stated in the *I Ching* (Book of Changes): "A cow tied up is taken by a traveler, bringing disaster to the villagers." Liu Hejian wrote *Yuan Bing Shi* (Tracing the Origins of Diseases), basing his theory on the Five Movements and Six Qi, asserting that all diseases originate from Wind, Cold, Summer-heat, Dampness, Dryness, and Fire, with no exceptions. He failed to realize that diseases caused by miscellaneous qi are a hundred times more numerous than those caused by the Six Qi. He did not understand that the Six Qi are limited and measurable, whereas miscellaneous qi is infinite and immeasurable. Focusing solely on the Six Qi while ignoring miscellaneous qi cannot possibly encompass all diseases under heaven!