In ancient Greece, there was a theory of four elements. The four elements include fire, water, earth and air. A Greek philosopher Anaximander developed this theory, and he thought that a kind of original substance formed the four elements. At the same time, in ancient China, there was a theory of five elements. The five elements include wood, fire, earth, metal and water. They were formed by a kind of original substance which was called Qi. In the Warring-States Period, Zou Yan, a thinker of Qi State, developed the theory of the five elements. He connected the theory of the five elements with the theory of Yin and Yang, and founded the doctrine of the Yin-Yang and Five Elements. Zou Yan gave a forced interpretation to this doctrine and used it to explain the events of the society and prophesy the future. Qin First-Emperor accepted this doctrine, because he needed it to justify his imperial reign. Except political use and philosophical use, the theory of the five elements was also used widely by the traditional Chinese medical science.

        Five elements are correlative. The relations of the five elements include promotion and restraint. The wood promotes the fire, the fire promotes the earth, the earth promotes the metal, and the metal promotes the water. Why? The wood can be burning and become the fire, and the ash formed the earth. In the earth, there are mineral resources of the metal. The metal can melt and become liquid as the water.

        As for the relations of restraint, the wood restrains the earth, the fire restrains the metal, the earth restrains the water, the metal restrains the wood, and the water restrains the fire. Why? A sprout breaks through the earth and becomes a big tree. A hoe or a spade has a wooden handle. The fire can melt the metal. The earth can be used for embanking rivers against floods. An ax or a saw has a metal blade. The water can extinguish the fire.

        Five elements are abstracted to five attributes of many things such as seasons, climate, directions, colors, internal organs and taste so on. Spring, wind, east, green, liver and sour belong to wood. Summer, hotness, south, red, heart and bitter belong to fire. Autumn, dryness, west, white, lung and piquancy belong to metal. Winter, coldness, north, black, kidney and salt taste belong to water. Center, wetness, yellow, spleen and sweet belong to earth. The sixth month of the Chinese Lunar Calendar belongs to earth. In the Pre-Qin Period, heart belonged to earth. However, in the Han Dynasty, heart started to belong to fire because of political need. Since the Han Dynasty, the theory of five elements had been steady.

        The theory of five elements is used for diagnosis, therapy and pharmacy of the traditional Chinese medical science. For example, the face of a patient who has a nephropathy is a little black. Recent years, an herb Guanmutong (Caulis Aristolochiae Manshuriensis) has been forbidden, because the excessive dose of this herb is nephrotoxic and even induces acute renal failure. The faces of the patients whose kidneys are damaged by Guanmutong are a bit dark.

        The theory of five elements is very deep, and this article only can show some basic contents of it. In ancient times, the theory of five elements was used too widely. If a person couldn’t explain a thing or a phenomenon, he would easily attribute it to the movement of five elements. This kind of attitude seriously hampered the development of ancient Chinese science. Since the early days of the 20th century, many scholars started to be against the theory of five elements. Nowadays, the theory of five elements is only used by the traditional Chinese medical science, because leastways it is helpful and effectual in the traditional Chinese medical science. So we should treat it rightly.

        Yin and Yang are two of the basic terms of the traditional Chinese philosophy. The two terms are also used in the theory of the traditional Chinese medical science. Ancient Chinese often explained many things and phenomena in the world by the concepts of Yin and Yang.

        Yin and Yang can show abstract attributes, and they also can denote material things. So they include materialist dialectics, and they surpass materialist dialectics which is full of abstract concepts.

        About abstract attributes, Yin and Yang are contrary as negative and positive. In the traditional Chinese philosophy, all things which are related can be defined to Yin or Yang in the world. For example, the sun belongs to Yang, and the moon belongs to Yin; the water belongs to Yin, and the fire belongs to Yang; the women belong to Yin, and the men belong to Yang. So we can summarize the method of defining Yin and Yang. The things which are cold, dull, down, declining, inhibiting or condensed belong to Yin. The things which are warm, bright, up, rising, stimulant or evaporating belong to Yang. The north of a mountain and the south of a river belong to Yin. The south of a mountain and the north of a river belong to Yang. If we pay attention to a fish pond in a sunny day of winter, we can see fishes gathered in the north of the pond. Why? They can enjoy the sunshine.

        When Yin and Yang denote material things, they belong to Qi. Qi is a kind of extremely small substance, and it forms all things of the world. In ancient Greece, the atomism of Democritus said that the basic components of the entire universe were simple, minute, indivisible, and indestructible particles. The theory of Qi is similar to the atomism, but Qi has rich connotations. Qi includes Yang-Qi and Yin-Qi. Yang-Qi and Yin-Qi are often called Yang and Yin for short. A body has Yang-Qi and Yin-Qi. If the two matters are unbalanced, the person feels sick. If Yang-Qi is excessive, the person is hyperpyretic, his tongue fur is yellow, his urine is yellow, and his feces are dry. If Yin-Qi is deficient, the person has low fever and night sweat, and his tongue fur is less. If Yin-Qi is excessive, the person feels cold, his tongue fur is white and thick, his feces are watery, and his abdomen has cold pain but he refuses to press it. If Yang-Qi is deficient, the person feels cold, he is languid and lethargic, he is willing to press his abdomen, and his urine is more and colorless. The basic principle of cure is to strengthen the deficient and weaken the excessive. The principle of strengthening the deficient is to reinforce Yang-Qi or Yin-Qi, and the principle of weakening the excessive is to use the medicine of cold attribute to clear heat away or use the medicine of hot attribute to warm up.

        The attributes of Yin and Yang are not absolute. We can say Qi belongs to Yang, and blood belongs to Yin, and we can say Yang-Qi and Yin-Blood. Why? Qi and blood are two different kinds of substances, but they can’t be said to be opposite. However, Qi is evaporating and blood is condensed, so we can say Yang-Qi and Yin-Blood.

        Yin and Yang move all the while. For example, the Qi of nature includes Yang-Qi and Yin-Qi. In the daytime, Yang-Qi is dominant. In the nighttime, Yin-Qi is dominant. In the noon, Yang-Qi is the strongest, but after the noon Yang-Qi declines gradually, and Yin-Qi rises gradually. In the midnight, Yin-Qi is the strongest, but after the midnight, Yin-Qi declines gradually, and Yang-Qi rises gradually. Why do persons who are critically ill always die at late-night time? It is because at that time Yang-Qi which can strengthen and promote the vitality of a human is very weak.

        The contents of the theory of Yin and Yang are very rich, and this article only refers to some basic contents, but it is helpful for a Westerner to understand Yin and Yang which belong to the important thoughts of Oriental people.

        In ancient Greece, there was a theory of four elements. The four elements include fire, water, earth and air. A Greek philosopher Anaximander developed this theory, and he thought that a kind of original substance formed the four elements. At the same time, in ancient China, there was a theory of five elements. The five elements include wood, fire, earth, metal and water. They were formed by a kind of original substance which was called Qi. In the Warring-States Period, Zou Yan, a thinker of Qi State, developed the theory of the five elements. He connected the theory of the five elements with the theory of Yin and Yang, and founded the doctrine of the Yin-Yang and Five Elements. Zou Yan gave a forced interpretation to this doctrine and used it to explain the events of the society and prophesy the future. Qin First-Emperor accepted this doctrine, because he needed it to justify his imperial reign. Except political use and philosophical use, the theory of the five elements was also used widely by the traditional Chinese medical science.

        Five elements are correlative. The relations of the five elements include promotion and restraint. The wood promotes the fire, the fire promotes the earth, the earth promotes the metal, and the metal promotes the water. Why? The wood can be burning and become the fire, and the ash formed the earth. In the earth, there are mineral resources of the metal. The metal can melt and become liquid as the water.

        As for the relations of restraint, the wood restrains the earth, the fire restrains the metal, the earth restrains the water, the metal restrains the wood, and the water restrains the fire. Why? A sprout breaks through the earth and becomes a big tree. A hoe or a spade has a wooden handle. The fire can melt the metal. The earth can be used for embanking rivers against floods. An ax or a saw has a metal blade. The water can extinguish the fire.

        Five elements are abstracted to five attributes of many things such as seasons, climate, directions, colors, internal organs and taste so on. Spring, wind, east, green, liver and sour belong to wood. Summer, hotness, south, red, heart and bitter belong to fire. Autumn, dryness, west, white, lung and piquancy belong to metal. Winter, coldness, north, black, kidney and salt taste belong to water. Center, wetness, yellow, spleen and sweet belong to earth. The sixth month of the Chinese Lunar Calendar belongs to earth. In the Pre-Qin Period, heart belonged to earth. However, in the Han Dynasty, heart started to belong to fire because of political need. Since the Han Dynasty, the theory of five elements had been steady.

        The theory of five elements is used for diagnosis, therapy and pharmacy of the traditional Chinese medical science. For example, the face of a patient who has a nephropathy is a little black. Recent years, an herb Guanmutong (Caulis Aristolochiae Manshuriensis) has been forbidden, because the excessive dose of this herb is nephrotoxic and even induces acute renal failure. The faces of the patients whose kidneys are damaged by Guanmutong are a bit dark.

        The theory of five elements is very deep, and this article only can show some basic contents of it. In ancient times, the theory of five elements was used too widely. If a person couldn’t explain a thing or a phenomenon, he would easily attribute it to the movement of five elements. This kind of attitude seriously hampered the development of ancient Chinese science. Since the early days of the 20th century, many scholars started to be against the theory of five elements. Nowadays, the theory of five elements is only used by the traditional Chinese medical science, because leastways it is helpful and effectual in the traditional Chinese medical science. So we should treat it rightly.