In Ancient Greece, several philosophers and historians analysed and described elements we now recognize as classical republicanism. Traditionally, the Greek concept of "politeia" was rendered into Latin as res publica. Consequently, political theory until relatively recently often used republic in the general sense of "regime". There is no single written expression or definition from this era that exactly corresponds with a modern understanding of the term "republic" but most of the essential features of the 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.