At Republic 462a-3, Plato provides an account of political unity summarized in the following claims: PU1--Political unity is the sharing of pleasures and pains in common; PU2--The unity of a polis resembles the unity of an individual; PU3--Political unity is the greatest good for a polis. Aristotle criticizes the coherence of these claims arguing that if anything becomes completely unified it becomes an individual and ceases to be a state. Since the greatest good for a city preserves it, a city cannot be unified as an individual is unified. Robert Mayhew has recently defended the philosophical significance of Aristotle's objections. Mayhew is right. Aristotle's objections are significant, but this is because they require a more thorough explication of the Platonic view. This paper reconstructs the Platonic view, shows that a more careful reading avoids the Aristotelian criticisms, and then shows that Aristotle endorses the reconstructed view.
