Read Book IV and Book V of Aristotle's Nicomachean Ethics. In Book IV, Aristotle explains how we may determine what is virtuous through the doctrine of the mean using examples of individual virtues such as bravery, generosity, and temperance. In Book V, Aristotle discusses the virtue of justice, which carries an exalted status among the virtues. Aristotle makes a distinction between two different but related types of justice: the general and the special (or particular).
Of general justice, he writes, "this type of justice then, is complete virtue, not complete virtue unconditionally, but complete virtue in relation to another. And this is why justice often seems to be supreme among the virtues, and 'neither the evening star nor the morning star is so marvelous,' and the proverb says 'And in justice all virtue is summed up'." As you will see, Aristotle's conception of justice stands in sharp contrast to that of Plato's, with the realization that individual justice is inextricably tied to the common good.