Socrates is here recapitulating the argument he employed against Thrasymachus when the Sophist argued that a ruler benefits by seizing all the power and wealth that he can, thereby benefiting himself. No, says Socrates, we have already agreed that the business of the ruler is to benefit the citizenry, and we have agreed that he is a wage-earner at one and the same time.
Socrates, in his limiting the laws in the ideal state, seems here to be anticipating a bad state of affairs in which the citizenry spends all of its time neglecting its duties to litigate disputes in courts of law, disputations conducted in many instances by students of sophistry during Plato's own life. And, Socrates argues, we have all witnessed those states in which flatterers and hangers-on besiege legislative bodies in an attempt to cajole lawmakers, either through sugared compliments or outright bribery, into making new laws or abrogating ancient laws for the flatterers' gain.
One further point here: Had Plato lived to see the fall of empires other than those of ancient Greece, he would not have been surprised to note that in almost every case, the fall of a given state is signaled by its reliance on hired foreign soldiery (the mercenaries analogy Adeimantus refers to) who abdicate their responsibility to the state in its direst need. For Plato's ideal state, such is not the case with the auxiliaries, native-born and educated citizens who function well and happily in their class, whose material needs are few and provided for by the state.
As we progress in the dialogue, we are ready to seek and fix a definition of the just state.
