Systematic political thought in ancient Greece begins with Plato, and quickly reaches its zenith in the rich and complex discussions in Aristotle's Politics. The political theories of both philosophers are closely tied to their ethical theories, and their interest is in questions concerning constitutions or forms of government. Herodotus sketches a fascinating debate by proponents of three forms of government: democracy, monarchy, and oligarchy. In Euripides' Suppliant Maidens, there is a debate between Theseus, champion of Athenian democracy, and a messenger from Creon, ruler of Thebes. Among Plato's predecessors there was a tradition of political thought and debate, but he was the first Greek thinker to undertake a careful, systematic analysis of fundamental questions in political philosophy. This article discusses Socrates' influence on Plato. It then looks at Plato's masterpiece, the Republic, and considers his model of an ideal constitution. It concludes with a discussion of Aristotle's complex and sophisticated analysis of political constitutions.