This symbol, commonly known as the T'ai Chi Chu symbol, or Yin-Yang symbol has its roots in ancient Chinese cosmology. At this time, The Yin Yang School was founded by Tsou Yen. In relationship to the elements, wood and fire belong to the yang, and water and meter to yin.
Earth belongs to both yin and yang because it assists both.
The yin and yang only represent opposite poles NOT good or evil. One of the first religions to use the Yin and Yang symbol was Confucianism. The Shih Ching and the I Ching were the first Confucius classics to feature the Yin and Yang. They are represented by the T'ai Chi, a diagram of an egg in which dark and light stand for yolk and white. It symbolizes the origin of all creation.