The yin / yang symbol is ancient. It first appeared in Chinese historical documents nearly three thousand years ago. The diagram which most people are familiar with as the yin / yang symbol is also known as the Tai Chi symbol.
The original meaning and characteristics of these two basic qualities come from: 1) the dark (yin) shady side of a mountain, 2) the light (yang) sunlit side of a mountain. In place of the mountain it is considered that a person is standing and facing away from the sun. Therefore the front of the body is relatively yin and the back of the body is relatively yang.
"The One Begets the Two". Chinese philosophers have over a period of several hundred years differentiated the chi of the Universe into two forces, yin and yang. The quality of yang was more rarefied, immaterial and more vast, it therefore floated upwards to form the Heavens. Yin was more condensed and material, it sank down and created Earth. As a theory yin / yang is a view of the Universe based upon centuries of experience and observation by the Chinese people.
It should be noted that it is only a theory. However, it is an all encompassing, yet flexible, theory and at the same time a simple tool that, once learnt, can be used to explain any number of phenomena. Its qualities are not exclusive, but complementary and relative. Life is not black and white, but a scale of colours ranging from one end of the spectrum to the other and always changing.
The Yin / Yang Symbol
1. The circle symbolizes the wholeness and infinity of chi. There is no beginning nor ending, and pervades through everything. This outer circle is the cosmos that contains the yang (light) and the yin (dark).
2. The dividing line between the two sectors is a curved one. This denotes movement and a constant flowing of yin into yang and yang into yin. It signifies the eternal motion of the combined elements.
3. Within the largest portion (when it has peaked and grown as big as it possibly can) of each colour there is a dot of the opposing colour. This can be considered as a small seed. Therefore we see that there is a small black dot (seed) in the white section and a small white dot (seed) in the black section. Everything contains the seed of its opposite within it. This is symbolic that all things contain both yin and yang.
4. The two colours are in equal proportion, equally balanced. When there is more of one aspect, then there is less of the other.
The relationship of Yin to Yang
Although yin and yang may appear to be opposites, they only exist by virtue of each other. Things are yin or yang only in relation to other things. i.e. dark and light; night and day; earth and heaven; front and back; down and up; cold and hot. It must be understood that one thing can be yin to another and yang in relation to a third, i.e. earth is yin in relation to heaven; heaven is yang in relation to earth; earth is yin in relation to the sun (which is hotter) earth is yang in relation to the moon (which is cooler) Or: tepid is yin in relation to hot; fiery hot is yang in relation to hot; icy is yin in relation to cold; moderately cold is yang in relation to cold.