Classifying Constitutions: Aristotle's Comparative Politics

Aristotle and his students reportedly collected and studied the constitutions of 158 Greek cities, making him a pioneer of comparative politics. In the Politics he classified constitutions by two questions: how many rule, and in whose interest? Rule by one, few or many can be correct if it serves the common good, giving monarchy, aristocracy and what he called polity. Each has a deviant form that serves only the rulers: tyranny, oligarchy and democracy, which he understood as rule by and for the poor.

Aristotle argued that the most practical good constitution is often a polity, mixing oligarchic and democratic features and resting on a large middle class, which is less prone to the extremes of rich and poor. His approach was empirical, comparing real states, unlike Plato's ideal city. Later thinkers, including Polybius and the framers of mixed constitutions, drew on his analysis.