Political philosophy
Political philosophy is the branch of philosophy that deals with fundamental questions about politics: the existence of the state, the extent of liberty, the pursuit of justice, the source of rights and the duties of citizens. One of the earliest political philosopher was Plato of Greece, whose Republic greatly influenced later political thought. Plato's student, Aristotle, further systematized the study of politics in philosophy and his principles were carried through the Middle Ages by the Scholastic philosophers such as Thomas Aquinas. In the Renaissance era, Machiavelli started the realist approach of political theory, which was also reflected in the writings of Thomas Hobbes. Another major turning point in politcal philosophy was the Enlightenment, where the foundation of modern liberal democracy was laid.
For many political philosophers, these questions are answered in part by what has been dubbed a social contract theory accounting for the origin of governments - this approach started with Thomas Hobbes and John Locke, but has been revived in recent years with the work of the American philosophers John Rawls and Robert Nozick.