Metal, wood, water, fire, soil is the ancient Chinese. In our ancestors viewpoint, wood is from soil, so wood can defeat soil; axe is a metal tools can chop woods, so it is the antiagonist of woods; fire can molten the metal, so fire can defeat metal; water can be fireless, so water is the opposite of fire; finally soil can manage water, flood.
As usual, ancient Chinese used this theory to explain vicissitude of reign of dynasties in Chinese old history. In this cycle of history, many a comedy or tragedy is shown on.
