The burden of the discussion has now shifted. At first, the only challenge was to define justice; now justice must be defined and proven to be worthwhile. Socrates has three arguments to employ against Thrasymachus’ claim. First, he makes Thrasymachus admit that the view he is advancing promotes injustice as a virtue. In this view, life is seen as a continual competition to get more (more money, more power, etc.), and whoever is most successful in the competition has the greatest virtue. Socrates then launches into a long and complex chain of reasoning which leads him to conclude that injustice cannot be a virtue because it is contrary to wisdom, which is a virtue. Injustice is contrary to wisdom because the wise man, the man who is skilled in some art, never seeks to beat out those who possess the same art. The mathematician, for instance, is not in competition with other mathematicians.
Socrates then moves on to a new argument. Understanding justice now as the adherence to certain rules which enable a group to act in common, Socrates points out that in order to reach any of the goals Thrasymachus earlier praised as desirable one needs to be at least moderately just in the sense of adhering to this set of rules.
Finally, he argues that since it was agreed that justice is a virtue of the soul, and virtue of the soul means health of the soul, justice is desirable because it means health of the soul.
Thus ends Book I. Socrates and his interlocutors are no closer to a consensus on the definition of justice, and Socrates has only advanced weak arguments in favor of justice’s worth. But the terms of our challenge are set. Popular, traditional thinking on justice is in shambles and we need to start fresh in order to defeat the creeping moral skepticism of the Sophists.
While The Republic is a book concerned with justice, it also addresses many other topics. Some scholars go so far as to say that the book is primarily about something other than justice. Critic Allan Bloom, for instance, reads the book first and foremost as a defense of philosophy—as Socrates’s second “apology.” Socrates was executed by the city of Athens for practicing philosophy. The leaders of Athens had decided that philosophy was dangerous and sought to expel it from their city. Socrates had called the old gods and the old laws into question. He challenged, and asked others to challenge, the fundamental beliefs upon which their society rested.
In The Republic, Bloom says, Plato is trying to defend the act for which his teacher was executed. His aim is to reveal why the philosopher is important, and what the philosopher’s relationship to the city should be. While a philosopher is potentially subversive to any existing regimes, according to Plato, he is crucial to the life of the just city. Plato wanted to show how philosophy can be vital to the city. Bloom calls The Republic the first work of political science because it invents a political philosophy grounded in the idea of building a city on principles of reason.