There are many contending definitions of the term Virtue. To be virtuous one must possess Merit, Valor, and have beneficial qualities. One must know and act upon what is good, what is right. Plato expresses in the "Republic- that a person and later a state must aim to achieve the four principal virtues. The four virtues consist of, courage, temperance, wisdom and justice. For Socrates a virtue is a particular thing or attribute. It is something possessed by the individual. Socrates holds that the principal virtue for man is justice or his sense of justice. He believes that temperance, wisdom and knowledge balanced equally together create harmony which then produces justice. .
The subject matter of the "Republic- is the nature of justice and it's relation to human existence. Book I of the "republic- contains a critical examination of the nature and virtue of justice. Socrates engages in a dialectic with Thrasymachus, Polemarchus and Cephalus, a method which leads to the asking and answering of questions which directs to a logical refutation and thus leading to a convincing argument of the true nature of justice. Socrates attempts to show that certain beliefs and attitudes of justice and its nature are inadequate or inconsistent, and present a way in which those views about justice are to be overcome.
Traditionally justice was regarded as one of the cardinal virtues; to avoid injustices and to deal equitable with both equals and inferiors was seen as what was expected of the good man, but it was not clear how the benefits of justice were to be reaped. Socrates wants to persuade from his audience to adopt a way of estimating the benefits of this virtue. From his perspective, it is the quality of mind, the pysche organization that enables a person to act virtuously. It is the opposition between the two types of assessment of virtue that is the major theme explored in Socrates' examination of the various positions towards justice.