Now, in furthering his concept of the Ideal State, Socrates divides the citizens into three groups: the Guardians are divided into two groups, the rulers and the auxiliaries; the rulers take priority in ruling the state, and the auxiliaries aid them. The third group is essentially the same as has been previously discussed, the craftsmen. As we might expect, the rulers are the very best of the Guardians; they must be older and more experienced men. These rulers must be incorruptible and impervious to bribes; in their youth and as they mature, they will have been tested to ensure their honesty. In other words, the rulers will rule as heads of state; the auxiliaries will police and defend the state; the craftsmen will conduct the necessary day-to-day business of the state.
At this point in the conversation, it occurs to Socrates that the three classes may at some point encroach upon one another and cause discord in the state. What if, for example, any member of a given class asks how he came to be so classified?
Socrates proposes that the citizens be told "just one royal lie," a "needful falsehood." This falsehood is to take the form of a story, the Myth of the Metals, a myth that Socrates discusses in the text. Glaucon is extremely doubtful about the efficacy of this "royal lie" and so is Socrates, but he is hopeful that the myth will ensure the citizens' loyalty to the community and to their respective classes.
Socrates concludes Book III with a few other stipulations having to do with the respective classes. All of these stipulations are intended to ensure the harmony of the state.
