external image yin-yang.jpgIn Chinese philosophy, the concept of yin yang is used to describe how seemingly disjunct or opposing forces are interconnected and interdependent in the natural world, giving rise to each other in turn. The concept lies at the heart of many branches of classical Chinese science and philosophy, as well as being a primary guideline of traditional Chinese medicine,and a central principle of different forms of Chinese martial arts and exercise, such as baguazhang,taijiquan, and qigong. Many natural dualities — e.g. dark and light, female and male, low and high — are viewed in Chinese thought as manifestations of yin and yang. "Yin means dark and cold, while Yang means bright and hot. The idea of Yin-Yang originated from the ancient Chinese philosophy of Fu Xi (伏羲)."
According to the philosophy, yin and yang are complementary opposites within a greater whole. Everything has both yin and yang aspects, which constantly interact, never existing in absolute stasis. Compare wuji. Yin and yang is symbolized by various forms of the Taijitu. It is commonly believed (especially in the West) that yin and yang correspond to "good" and "evil"; however, this was not an aspect included in ancient forms of the philosophy. The idea of yin and yang having a "moral" aspect was originated by the Confucian school (most notably Dong Zhongshu) around the second century BCE.