The divided circle in the photograph is the symbol of yang and yin. The eight trigrams or figures of three that surround it are the ba gua said to hold the key to knowledge. Many centuries ago, Chinese philosophers identified yang and yin as the major forces, or energy modes, in life. The Chinese believed that the two forces were within every natural object and that the activity of one or the other controlled the universe. The two were constantly interacting. In a process that never ended, they produced each other, influenced each other. Thus, any single object could show the characteristics of yin at another moment. 

             Yang was the positive force and was masculine in character. It was active, warm, dry, bright, and aggressive. The sun and the Heaven were considered yang. So was fire, the south side of a hill, and the north bank of a river. Horses were yang because they rose front-end first. The shen, or good spirits, were yang. Men, too, were predominantly yang. They were celestial and of great worth. 

             Yin was the opposite force and was feminine in character. It was dark, cool, wet, mysterious, secret, and submissive. Shadows and Earth were yin. So was the north side of a hill and the south bank of a river. Camels were yin because they rose hind-end first. The gui, or evil spirits, were yin. Women, too, were predominantly yin. They were earthly and of no great worth. 

             As legend goes, either yang or yin controlled the seasons and life. To achieve the perfect life, the correct balance had to be maintained between the forces of yang and yin. Care had to be taken not to upset the delicate harmony of the two forces. If it were upset, the result could be a change in the natural order of things. Too much yang in the person’s actions, for example, might cause drought, famine, and fire. Too much yin, on the other hand, might bring out-of-season rains and floods. Life for the Chinese, then, was a striving to achieve harmony with nature and not upset the balance of yang and yin.