Why this world is unfair? If every persons become a same circumstances, nobody work completely. For example, water flow from high to low. This difference altitude bears world economics motive powers. In this,high means rich and low means poor. Then look! There is a cataract. The cataract have a strong difference of altitude, so this causes a strong flow. The devil exist surely. He is the master of this world. He has been keeping situation of this world is unfair.