Socrates proposes to discover what justice is and hence whether it is good by building the best city “in speech,” for it will be easier to spot justice in the bigger thing first—the political community—before looking for it in the smaller thing, the individual. Yet the fact that the Republic does not end in Book IV, with its official definition of “justice”, but continues for six more books, suggests that this definition does not solve all the difficulties on the table. It does, however, help us see with greater clarity the problem of justice: Justice must include a sense of duty or obligation, to a whole greater than oneself, as Socrates’s captured beautifully in his account of political justice. But justice must also be good and even a very great good for the just themselves, which Socrates captured very well in his account of individual justice. By the end of Book IV, however, the challenge of Thrasymachus remains: Can the two senses of justice be put together into a coherent whole?