modern definition are present in the works of Plato, Aristotle, and Polybius. These include theories of mixed government and of civic virtue. For example, in The Republic, Plato places great emphasis on the importance of civic virtue (aiming for the good) together with personal virtue ('just man') on the part of the ideal rulers. Indeed, in Book V, Plato asserts that until rulers have the nature of philosophers (Socrates) or philosophers become the rulers, there can be no civic peace or happiness. A number of Ancient Greek city-states such as Athens and Sparta have been classified as "classical republics", because they featured extensive participation by the citizens in legislation and political decision-making. Aristotle considered Carthage to have been a republic as it had a political system similar to that of some of the Greek cities, notably Sparta, but avoided some of the defects that affected them. Ancient Rome Both Livy, a Roman historian, and Plutarch, who is noted for his biographies and moral essays, described how Rome had developed its legislation, notably the transition from a kingdom to a republic, by following the example of the Greeks. Some of this history, composed more than 500 years after the events, with scant written sources to rely on, may be fictitious reconstruction. The Greek historian Polybius, writing in the mid-2nd century BCE, emphasized (in Book 6) the role played by the Roman Republic as an institutional form in the dramatic rise of Rome's hegemony over the Mediterranean. In his writing on the constitution of the Roman Republic, Polybius described the system as being a "mixed" form of government. Specifically, Polybius described the Roman system as a mixture of monarchy, aristocracy, and democracy with the Roman Republic constituted in such a manner that it applied the strengths of each system to offset the weaknesses of the others. In his view, the mixed system of the Roman Republic provided the Romans with a much greater level of domestic tranquillity than would have been experienced under another form of government. Furthermore, Polybius argued, the comparative level of domestic tranquillity the Romans enjoyed allowed them to conquer the Mediterranean. Polybius exerted a great influence on Cicero as he wrote his politico-philosophical works in the 1st century BCE. In one of these works, De re publica, Cicero linked the Roman concept of res publica to the Greek politeia. The modern term "republic", despite its derivation, is not