The aim of this paper is to present the topics and content of Plato's dialogue The Republic, which is his most famous work. In The Republic, Plato discusses justice and injustice by taking the state as an enlarged individual. The fundamental virtue permeated by this state is justice, followed by wisdom, courage, and moderation. Plato emphasizes how important it is for everyone in the state to do their job for which they are in charge, and not to interfere in other people's business. The hierarchical social structure of the state is divided into philosophers as the wisest in the state and leaders of other citizens, then into guards, who are brought up in special conditions, and their main task is to protect their citizens and subdue enemies. Producers, ie craftsmen and farmers, are appointed as the third class. Plato's state will be sustainable only if the individual is truly and justly connected with his fellow citizens and with the state.