2025 Theses Doctoral

Nature and Justice in Plato's Republic and Antiphon's On Truth

Lea, Luke

This dissertation makes two proposals. First, that the aims of the central ethical argument of Plato’s Republic include showing that the just life is better than the unjust by nature for the individual human being who lives it. Second, that a major motivation for this project is the need to combat notable immoralist arguments for the opposite position: that injustice or the unjust life is by nature better than justice for the individual human being.

The clearest expression of this immoralist framework in the surviving literature is found in the fragments from Antiphon’s On Truth, which lay out an ethical position that combines rational egoism (the view that one should maximize one’s self interest, in the sense that it is rational to do so) with the view that the fundamental human good consists in physiological flourishing, the specifics of which are determined by human nature.

On such a view, justice is not a value, but a hindrance to one’s pursuit of a good life. Plato rejects Antiphon’s conclusions, but accepts the importance of the challenge as well as the legitimacy of human nature as the criterion. He thus takes it upon himself to show that justice is good for the individual human being by nature.