In his Republic, Plato suggests that in an "ideal state", the members should be divided into three different classes: philosopher-king (ruler), guardian and merchant. Philosopher-king is to rule the whole state, guardian is to keep the order and maintain security within the state or fight the war with another state, and merchant is to satisfy the material needs of the members of the state.
Moreover, Plato suggests a rigid hierarchy between the three classes: Philosopher-king is the highest class, which is to rule. The guardian is obliged to unconditionally comply with the philosopher-king, and merchant is the lowest class, and must comply with the philosopher-king and the guardian.
People of one class can't interfere with the affairs of another class, because Plato believes that people have different skills and innate aptitudes as he says "...no two of us are born exactly alike. We have different natural aptitudes, which fit us for different jobs". This is one of the points that Plato criticizes democratic regime; in democratic regime, one person can interfere into another's affair, this would cause "injustice".
In his Republic, Plato always criticizes democratic regime. He claims that democratic regime is an unjust regime, the regime by opportunity not capacity, the regime that causes upheaval and confusion among the people. Democratic regime is like a toy regime: people can change administration all the time and people's too much choice would lead them to confusion. Democracy makes the poor poorer and the rich richer.
Plato's ideal state should be fairly small and justly adequate. Too big state would be very hard to govern. By justly adequate, Plato wants to mean that the material needs should be equally shared by the three classes of the s ...