 This city has three classes (genê) of citizens. The rulers are characterized by their knowledge about and devotion to the welfare of the city. The auxiliaries are the warrior class that helps the rulers. These two are collectively the guardians of the city (413c–414b; 428c–d). Finally, there are the farmers, artisans, and merchants – in general those concerned with the production of material goods necessary for daily life (369b–371e). The importance of this structure is that it allows Socrates to define virtues of the city by relations among its parts. These virtues are justice, wisdom, courage, and moderation. For instance, justice in the city is each one performing that function for which he is suited by nature and not doing the work that belongs to others (433a–b). One’s function, in turn, is determined by the class to which he belongs. So rulers should rule and not amass wealth, which is the function of the farmers, artisans, and merchants; if the rulers turn from ruling to money-making they are unjust.