Early societies included bands, tribes, and chiefdoms that evolved into states with different forms of government. The Greeks established some of the first city-states and experiments with different systems of rule, including monarchy, oligarchy, democracy and republics. Key Greek thinkers like Socrates, Plato, and Aristotle influenced Western political philosophy through examining different forms of government and their impacts on society. The Romans established a republic with elected representatives and laws governing citizens and state affairs.