It seems that this concept might have its origins in the old rural religions, and it can also be found in the Confucianism and Taoism. One of the roots of Yin-Yang is found in the I-Ching book which is about the natural phenomena of the universe.
The Chinese ideograms representing the I-Ching are: the first ideogram which means "book" and the second ideogram which means "ability of change"; this ideogram is formed by the combination of a symbol representing the sun (Yang) and another one representing the moon. The sun is on the upper side of the symbol and the moon is on the lower part of it.
After observing the universe, the ancient Chinese realized that the universe was constantly changing. They also believed that, although this change was continuous, there were seasonal and annual periods, too. From these periods some stable and constant roles are derived: the so called hexagrams. However, it is not easy to find the way to obtain this stable and constant rule in the universe and then apply these rules to human activities.
Yin-Yang concept is especially important in Taoism. It is just once mentioned in Tao Te Ching, but the whole book is full of examples that try to explain it; According to taoists the Yin-Yang concept is born from the "Qi"(vital energy).
Following this interpretation, Yin and Yang are seen as Qi (in both Yin and Yang forms) operating in the universe as two opposed forces. Thus, a force arising from the interplay between Yin and Yang becomes a context in which yinyang is seated and functions. “Everything is embedded in Yin and embraces Yang.
This is a criterion of division and classification of natural phenomena and their transformation. In this respect, Qi can manifest itself as “matter” and “energy” (Vital energy).
It seems that every living thing, object or thought has a complementary energy that is essential for its existence and, which at the same time, lies inside itself. This means that nothing exists in complete quietness or complete pureness but in continuous transformation. Moreover, any idea can be seen as opposing another idea depending on the point of view you are seeing it from.
It is also impossible an exact classification of Yin-Yang element, as these elements can be Yin or Yang depending on the element you are comparing it with. According to the earliest Comprehensive Dictionary of Chinese Characters Xu Shen's Shouwen Jiezi, Yin (陰), refers to “a closed door”, darkness and the south bank of a river and the north side of a mountain. This symbol can also be found in a simplified way (阴), making reference to the moon(月，yuè). Yang (陽) refers to “height, brightness and the south side of the mountain”. This symbol can also be found in the simplified way (阳), represented by the sun (日, rì). This indicates that Yang is the sunny side and Yin is the shady side of the hill. This effect of the sun exists at the same time over the hill.
Yin and Yang are opposite. Everything has its opposite; however this is not absolute, but something relative because nothing is completely Yin and nothing is totally Yang. For instance, winter is the opposite of summer but a summer day can be cold and just the other way round.
Yin and Yang are interdependent. There can't be one without the other. For instance, there can't be night without day.
Yin and Yang can each be subdivided into Yin and Yang. For example, an object can be cold or hot, but at the same time a hot object can be warm or extremely hot and a cold object can be just cool or frozen.
Yin creates and destroys Yang as well as Yang creates and destroys Yin. Yin and Yang form a dynamic balance: when one of them gets bigger the other decreases. When one of them increases too much, the other is forced to end in a new transformation. For instance, an excess of water vapor in the clouds (Yin) causes the rain (Yang).
Yin and Yang can change into their opposites. The day changes into the night, hot turns into cold and life turns into death. However, this transformation is also relative. The day turns into night but they both coexist at opposite ends of the earth.
There is Yin in Yang and there is Yang in Yin. There is always something of the other in each of them. For example, the seed in planted in winter but it grows in spring.
José L. MELERO
YIN 陰 YANG 陽