In fact, Plato made his argument for the worth of justice long before this, in Book VII. The true worth of justice, on this reading, stems from the connection of justice to the source of all worth in the universe, the Forms. Since the Forms are the ultimate good, and justice involves seeking, grasping, and imitating these, justice too is good and the just life is worthwhile. This is the interpretation that Aristotle favored, and contemporary philosophers such as Richard Kraut have attempted to revive this reading. Kraut explains this notion of worth in the following terms. For Plato, what makes a human life good, and a human value worthwhile, is its connection to an absolute external good, this external good being the Forms. He compares this Platonic point of view to the Christian worldview in which God is the greatest good, and bringing God into one’s life is what gives each life worth, and also to nineteenth century Romantic conceptions in which life only becomes worthwhile when it is not cut off from nature and the natural order. In all of these cases, the human good consists in relation to some higher, supreme good outside ourselves.

If knowledge of the form of the good is what makes the just life worthwhile, does anyone but the philosopher live a worthwhile life? If the Forms are the source of all worth and only the philosophers consort with the Forms, what can we say about everyone else? Do they have no chance at all to live a good life? Plato might respond to this question by stressing that any man can bring his soul toward the Forms to some extent by making sure that their soul is ordered and harmonious. In other words, by being just—by making sure that reason rules spirit and appetite—a man lives a worthwhile life even if he never grasps the Forms with his intellect.