Understandings of justice differ in every culture, as cultures are usually dependent upon a shared history, mythology and/or religion. Each culture's ethics create values which influence the notion of justice. Although there can be found some justice principles that are one and the same in all or most of the cultures, these are insufficient to create a unitary justice apprehension.
Justice as harmony: In his dialogue Republic, Plato uses Socrates to argue for justice that covers both the just person and the just City State. Justice is a proper, harmonious relationship between the warring parts of the person or city. Hence Plato's definition of justice is that justice is the having and doing of what is one's own. A just man is a man in just the right place, doing his best and giving the precise equivalent of what he has received. This applies both at the individual level and at the universal level.
A person's soul has three parts – reason, spirit and desire. Similarly, a city has three parts – Socrates uses the parable of the chariot to illustrate his point: a chariot works as a whole because the two horses’ power is directed by the charioteer. Lovers of wisdom – philosophers, in one sense of the term – should rule because only they understand what is good. If one is ill, one goes to a doctor rather than a psychologist, because the doctor is expert in the subject of health. Similarly, one should trust one's city to an expert in the subject of the good, not to a mere politician who tries to gain power by giving people what they want, rather than what's good for them.
Socrates uses the parable of the ship to illustrate this point: the unjust city is like a ship in open ocean, crewed by a powerful but drunken captain (the common people), a group of untrustworthy advisors who try to manipulate the captain into giving them power over the ship's course (the politicians), and a navigator (the philosopher) who is the only one who knows how to get the ship to port. For Socrates, the only way the ship will reach its destination – the good – is if the navigator takes charge.