Justice in Plato vs. Justice in Aristotle
Usually when you hear that someone is a teacher you tend to believe that the ideas of his or her pupils would be somewhat similar to those in his or her teachings. Often enough the student decides to take what he or she learns from his teacher and expands or even opposes his teacher's ideas. Aristotle was a student of the often imitated, never paralleled, philosopher, Plato.

Although under the tutelage of Plato for over nineteen years and teaching at the Platonic Academy, Aristotle had many different views in regards to justice in society. Plato felt that justice was harmony, while Aristotle felt that it was in the common interest or in other words: justice was a compromise. I will attempt to provide a deeper understanding of this dilemma.
(Justice is harmony) One would tend to believe that peace, and good will among all individuals in a community would be the main ingredients necessary to encompass harmony, yet although at first a simple concept to conceive, the ultimate goal of achieving harmony (justice according to Plato) requires many different factors. These factors (or pillars) upon which justice in Plato is constructed include but are not limited to education, interdependence of a communities sub-units, philosophy, the separation of public and private life, truth, as well as no movement.
In Plato's Republic, justice is defined in many different ways, none of which seem to keep Socrates content.

Cephalus insisted that justice was telling the truth and paying one's debts. Polemarchus, Cephalus' son, maintained that justice was paying one's dues. Socrates refuted their argument by using a mad man as an example. He proved that if one man borrowed another man's knife and the owner of the knife went mad, it would not be just to return the knife to the rightful owner for the owner would be in possible danger of harming himself.

Under other circumstances such as a situation where the owner wanted to go hunting with his knife it would be just to return the knife to him or her.
Thrasymachus interjects that justice is that which is in the interest of the stronger party. When he emphasized "stronger party" he implied governing bodies such as political leaders. He said that a community's people would follow leaders because the leader's law would be justice and it would be the constitution of the community. The problem here is that corrupt officials may make laws and regulations that wouldn't be fair to all or even be in the worst interest of some.

Some officials would make laws to simply benefit their own interests. At one point Thrasymachus said that perfect injustice pays better than perfect justice. Socrates changed Thrasymachus' mindset by making him agree that justice was goodness and knowledge and injustice their opposites.Plato argues that a just state is achieved in a situation in which everyone does one's own job, where each part functions properly with an eye to the good of the whole.

In a just society, the rulers, the military, the working-class persons, all do what they ought to do. In a just society, their rulers are wise, the soldiers are brave, and the producers of material goods exercise self-control and are not overwhelmed by their desires for gain. (Great Thinkers of the Western World, Ian P. McGeal, editor.)
(Justice as compromise) Aristotle taught that justice was a compromise of the common interests.

The factors included in the belief of justice as a compromise are law, assumption of state and the assumption of man as political.