Hello, everyone. We've discussed about the origin and development of the traditional Chinese medicine in the last few lessons. Today we will talk about some of its basic theories and thoughts. Let's start from the Thought of Yin and Yang. The first topic is its origin. Who proposed the Yin and Yang first? It is hard to find evidence. However, it is widely accepted that it started from Shang Dynasty and developed well during Spring and Autumn Period. In the Chinese early characters - oracle bone inscriptions, there already existed the characters meaning "Yin" and "Yang". In the inscriptions of bronze, the words "Yin" and "Yang" can be used together. For example, there are phrases meaning "its Yin and Yang". However, when it comes to the very beginning of the thought, it can by traced to the Period of Fu Xi during Neolithic Period. Although Fu's Eight Trigrams failed to be handed down from past generations, its basic elements were similar to Zhou Yi's. These two Eight Trigrams all had two basic symbols - Yin hexagram and Yang hexagram. Then, what did these two symbols mean? There were many speculative explanations. Somebody believed they represented male and female genitals. Some thought they were refer to the sun and the moon. While others think they means a type of motion. Though explanations are various, they all mention about the basic elements of Yin and Yang. During the Spring and Autumn Period, "yi" combines itself with Yin and Yang which extended the origin of the thought to ancient times. According to the literatures in ancient times,the origin of Yin and Yang was closely related to the sun. For example, in the "Gu Liang Zhuan" we can see the sentence "the northern part of a river and the southern part of a mountain are called Yang". In the "Shuowen Jiezi", the meanings of the Yin and Yang were more clearly explained such as the sentence - "Ying, which means dark, refers to the southern part of a river and the northern part of a mountain" which is the same with the sentence above-mentioned. The difference between Yin and Yang is related to the geographical features in Central China. Both the southern part of a mountain and the northern part of a river are easier to be exposed to the sunshine, so it's warm there which is meant by Yang. however, the opposite two parts are relatively cooler, so they belong to Ying. Besides, many geographical names are related to the Thought of Yin and Yang. For instance, "Hua Ying" is the northern part of Huashan Mountain. and "Heng Yang" means the southern part of Hengshan Mountain. Also, we have the place "Jiang Yin" which locates in the south of Yangtze River. and "Luo Yang" that is in the north of Luo River. During the late Western Zhou Dynasty and middle Spring and Autumn Period, the concept of Yin and Yang extends to the "the breath of heaven and earth". For example, in the Zhou Dynasty, there was a man called "Bo Yang Fu" who used Yin and Yang to explain the phenomenon of earthquake. and began to discuss the effect of the changes of Yin and Yang on the human body. In 541 B.C., a doctor named "Yi He" believed that Yin and Yang belong to the breath of heaven. The breath of heaven can be divided into Yin, Yang, wing, rain, night and daytime. Yi He also used Yin and Yang to respectively explain the causes of febrile illness and the sickness caused by coldness. In the Spring and Autumn Period, Lao Tzu - founder of Taoism, said that "All things leave behind them Yin, and go forward to embrace Yang, while they are harmonised by the Breath of Vacancy." He believed that everything in the world is made of Yin and Yang which raised the Thought of Yin and Yang to the height of philosophy. The thought flourished during Warring States Period, Many schools (include the Yin-Yang school ) played active roles in developing it. Chaung Tzu not only combined "the breath" with Yin and Yang, but also discussed about the unity and opposition of Yin and Yang. He also claimed that the combination of Yin and Yang can create all things on earth. What does it meanďź It points out the importance of the harmony between Yin and Yang to the development of all things on earth. In State of Qi, scholars of Jixia Academy combined Yin, Yang with Five Elements and then put forward the Five Elements Theory of Yin and Yang. While, in the Confucianism, Yin and Yang were related to Yi. The sentence that - the Yin and the Yang make up the Tao- emphasized the variation of Yin and Yang, which also caught the attention of scholars in the field of traditional Chinese medicine. After Han Dynasty, the Thought permeated into all aspects of social life. Dong Zhongshu introduced Yin and Yang to the relation between heaven and man. In the process, though the influence of Yin and Yang expanded because of its connection to society, politics and ethnics, its idealistic view of heaven and man made it hard to go further. Meng Xi and Jing Fang made their Theory of Gua Qi, in which the 64 Hexagrams matched with the four season, the twelve months, the twenty-four solar terms and the seventy-two pentads. People can use the hexagram to explain the relation between the changes in four seasons with the development of all things on earth. Unfortunately, their theory ends with failure because its advocation of the relation between Yin,Yang and disaster. To be concluded, traditional Chinese medicine uses the rational part in the Thought of Yin and Yang to make the basic theories and then inherit and develop the Thought. Class is over and in the next lesson we will talk about the core ideas of Yin and Yang.