Ralph Waldo Emerson once wrote “One man’s justice is another’s injustice.” This statement quite adequately describes the relation between definitions of justice presented by Polemarchus and Thrasymachus in Book I of the Republic. Polemarchus initially asserts that justice is “to give to each what is owed” (Republic 331d), a definition he picked up from Simonides. Then, through the unrelenting questioning of Socrates, Polemarchus’ definition evolves into “doing good to friends and harm to enemies” (Republic 332d), but this ....