The Republic is a classic work by an ancient Greek philosopher Plato.
There is one of the most famous dialogues of Plato about the arrangement of the state structure and the essence of the state (contemporary for Plato, of course, but also important nowadays because the whole modern so called 'European civilisation' is based, first of all, on ancient schemes).
The structure of Plato's dialogue is similar to others. Socrates and Glaucon are coming back to Athens from Piraeus. They are stopped by Polemarchus who invites them to visit him and talk. The subjects of a state and justice appeared during the conversation with Cephalus, the father of Polemarchus.