In his influential paper “A Fallacy in Plato’s Republic,” David Sachs charged Plato with committing a fallacy of irrelevancy. Plato’s Socrates is asked to show that justice understood as acting in conformity with conventional morality, so-called vulgar justice, is beneficial to the just person. Socrates actually demonstrates something else, namely that psychic justice, a state of internal harmony between parts of the soul, is beneficial to its possessor. A generation of Plato scholarship has reacted to Sachs’ reading of the Republic by using discussions of moral psychology and education elsewhere in the dialogue to bridge the gap between psychic justice and a conception of justice centered on the performance of moral actions. This paper presents a different way of responding to Sachs’ paper. Republic 4 contains not two but only one conception of justice, according to which justice is a power in the soul of individuals. Justice is a power whose nature it is to transmit itself to cities which achieve civic justice as they are formed by just individuals. Just actions which promote the good of others are the medium by which justice transmits itself to cities.
Payne, Andrew, "Justice as Self-Transmitting Power and Just Acts in Republic 4" (2011). The Society for Ancient Greek Philosophy Newsletter. 449.