Plato’s ideal government is given its legitimacy by having leaders who are “better” than the rest of the citizens. These Guardians are said to be fundamentally superior to the other citizens both because of their innate characteristics and because of their specialized training for being a ruler. They will be chosen to rule if they “in their whole life show the greatest eagerness to do what is for the good of their country, and the greatest repugnance to do what is against her interests” (Plato 412 a). They have the right and obligation to rule justly over the other citizens. None of the other citizens should have any reason to complain because these Guardian Kings, or Philosopher Kings, should be much better rulers than any of the other citizens would be.
In Locke and Rousseau’s versions of political theory, however, the state has power because it is made by and for the people, and therefore the people want to keep it in power. They enter into a contract with the government to support it and obey its laws in return for protection and security. Without government or society, people live in what Locke calls the “state of Nature.” Although they have more freedom in the state of Nature, they do not have any security and there is no all-encompassing law that is the same for everyone. There is no power greater than individuals, so there is no protection from unjust individuals or actions. If any individual wants to steal or murder, there is nothing stopping him from doing so.
Out of this situation, people form communities with more defined laws to “preserve his [the individual’s] property - that is, his life, liberty, and estate - against the injuries and attempts of other men” (87). The Social Contract is the agreement by the citizens to obey the rules of the state as long as they are just. Since these laws are made for the good of the citizens, the citizens support it and the government is given legitimacy.