In Plato's immortal philosophical treatise The Republic, a notion of the Good is advanced that defies subjectivity. Through Socrates, Plato illustrates that a rationalistic approach conjoining virtue and knowledge will yield certain objective truths about human nature and the ideal modes of human conduct. In a sense, these truths apply directly tołand correspond withłthe human soul and the human city. Because there is a hierarchy of values for Plato, and because the most sublime of values is the Form of the Good, so there will be only one state of excellence for both the soul and the city. It is to this observation that Plato dedicates the latter half of Book IV of The Republic.
Socrates, in the spirit of coming to the rescue of justice in every way possible, asserts in Book IV that the city "if it is rightly founded, is completely good" and that such a city will exhibit each of four cardinal virtues: it will be "wise, brave moderate, and just" (Grube 93). As Socrates fleshes out the nature of each of these virtues within the city, he observes that for the city to be wise, true wisdom must be found in its rulers. As it is only the carpenter that is supremely knowledgeable in his craft that is deemed a master, so too only a supreme knowledge of guardianship in the guardian class will imbue the city with true wisdom in governance and conduct (Grube 94).
Bravery is to be found in the army; this virtue will logically reside in "that part [of the city] which makes war