The city in speech
The ideal state is the perfectly just city Plato constructs "in speech" in the Republic. The platform reads it as the most famous and most misread political construction in the history of thought. Plato builds it not, in the first instance, as a practical blueprint but as a model — justice "writ large," easier to discern in the city than in the individual soul — and the platform reads much of the misreading of the Republic as the failure to grasp that the ideal state is primarily a device for understanding justice, and only secondarily, if at all, a programme for reform.
The structure
The platform reads the ideal state as a city of three classes mirroring the three parts of the soul: the producers (appetite), the guardian-soldiers (spirit), and the philosopher-rulers (reason). Its most radical and notorious features belong to the guardian class: the abolition of private property and private family among the rulers, the communal rearing of children, the equal participation of women in the highest offices, and the rigorous selection and education that produces the philosopher-king. The platform reads these proposals as following from a single principle — that the rulers must have no private interest that could compete with the good of the whole — rather than as arbitrary radicalism.
Blueprint or measure?
The platform reads the central interpretive question as whether Plato meant the ideal state to be built. He says it exists "perhaps as a pattern laid up in heaven," that whether it could ever be realised is a separate question, and that the philosopher who has seen it will order his own soul by it whether or not the city exists. The platform reads the ideal state primarily as a measure — a standard of justice against which every actual constitution falls short — and reads Plato's later turn in the Laws toward a detailed, workable second-best city as his own acknowledgement that the ideal is not a practical programme.
Why it matters for Virtue & Power
The ideal state is the platform's central case of utopian political thought — the construction of the perfectly just city as a way of thinking about justice itself — and the foundation of a tradition that runs from More and the Renaissance utopias to the modern critics who read it as the first totalitarian blueprint. The platform reads it without either reverence or the easy modern dismissal, in the Republic misunderstood.