Ruling only in four cases will lose power: Or was conquered by external forces; either ruled incompetent people to revolt; either make a strong and discontented middle-man group appears; either lost their own rule confidence and will. This reason is not four single function, there is always the same extent. Ruling class if they can prevent the generation of these four reasons can be permanently in power. The final decisive factor is the mental state of the ruling class itself.
Three kinds of people exist forever, fine people, middle people, inferior people in this world. They play the role of the finest people to defend their rights and status; middle and upper class people want to swap positions, and others under unexamined, but the vast number of groups have been utilized