The earlier discussion of the social contract and the sovereign explain how the body politic comes into being; the question of how it maintains itself calls for a discussion of law. Rousseau suggests that there is a universal and natural justice that comes to us from God, but that it is not binding. Evil people will not obey God's law, and so we must set up positive, binding laws within society, or else those who obey God's law will suffer at the hands of those who disobey it.
Rousseau defines law as an abstract expression of the general will that is universally applicable. All laws are made by the people as a whole and apply to the people as a whole: the law does not deal with particularities. The law can never deal with individual people or groups, so while it can say that a certain group should have certain privileges or that a certain person should be the head of state, it cannot determine which particular individual or group should receive these privileges.
The law is essentially a record of what the people collectively desire. A law can only be enacted if the people collectively agree on it, and it must apply to all of them. A declaration of the sovereign that applies only to certain people or certain objects is not a law, but a decree.
The existence of civil society hinges on the existence of laws. However, Rousseau acknowledges the problem of how laws should be laid down. How can a people as a whole sit down together and write up a code of law? There is not only the problem of how such a large number could write up such a document together, but also the problem that the people do not always know what they want or what is best for them. Rousseau's proposed solution comes in the form of a lawgiver.
An ideal lawgiver is not easy to find. He must be supremely intelligent, and willing to work selflessly on behalf of a people. Because the laws shape the character and behavior of the people to a great extent, the lawgiver must exhibit great insight. In order for the laws to be unbiased, the lawgiver should not himself be a citizen of the state to which he gives laws. He is outside and above the authority of the sovereign. Remarking on the difficulty of finding such a person, Rousseau notes: "Gods would be needed to give men laws."
Not only is there the difficulty of finding a lawmaker of genius who does not himself wish to govern; there is also the difficulty of making the people obey the laws. People are unlikely to simply accept the laws given to them by a particular person. Rousseau notes that throughout history, lawgivers have used the authority of God or some other divine power to support them. Moses, for instance, claims that God gave him the Ten Commandments. An appeal to the supernatural origins of the laws is generally a good means of ensuring that they are obeyed.
To a large extent, the agreement to live under certain established laws is what defines the social contract. In the Analysis section for Chapters 6-9 of Book I, we distinguished between civil and physical freedom, suggesting that we give up the latter and gain the former by entering into civil society. Physical freedom is characterized by the unbounded freedom to do whatever we like, following our instincts and impulses. Civil freedom places a check on our instincts and impulses, teaching us to think and behave rationally, and opening us up to the freedom of thinking for ourselves.
Rousseau is by no means the only philosopher to define "real" freedom not as an unbounded do-as-you- please, but as the ability to deliberate rationally. If our behavior is not restrained by laws of some sort, we are not free, but are rather slaves to our instincts and impulses. If our behavior is restrained by the laws of some outside force, then we are not free, but are slaves to that outside force. The only solution, then, is to define freedom as behavior that is restrained only by the laws of our own making. When we extend this solution to society as a whole, the only laws that can maintain the freedom of citizens are those laws that the citizens as a whole agree upon.
Rousseau is careful to distinguish between laws and decrees. Decrees are matters of day-to-day business: a leader appointing an attorney general, or the decision to condemn a traitor to death, or anything that deals with individuals or particular groups is a decree. Laws are made for the people as a whole by the people as a whole. They are the general guidelines under which a people chooses to live. As the restraints a people places upon itself, laws are what define their civil freedom.
Because laws represent the restraints of civil freedom, they represent the leap made from humans in the state of nature into civil society. In this sense, law is a civilizing force upon us, so it is no surprise that Rousseau believes that the laws that govern a people define their character to a great extent. In Discourse on Inequality, he asserts that it is bad government, and not human nature, that is the source of our evil. Here, he suggests that good government, or rather good laws, can make good people. People who agree voluntarily and as a group to abide by certain restrictions that will benefit all of them will likely become better people as a result.
Rousseau gives no practical solution as to how a code of laws is to be formed. On the contrary, he remarks at length as to how difficult it is to find someone who is up to the task. Because a set of laws largely defines the people who live under these laws, the lawgiver is responsible for determining what kind of people a certain state will produce. Thus, a lawgiver is neither what we might understand as a judge or legislator, nor even a political leader or dictator. The lawgiver should be understood as someone who invents a moral code. If we recall, morality is defined by rationality, rationality (according to Rousseau) comes into being with civil society, and civil society comes into being thanks to a lawgiver. We might even think of the lawgiver as a saint or prophet of sorts: it is no wonder that Rousseau associates the creation of laws with the supernatural.
Despite all his talk about the difficulties of lawmaking, Rousseau himself undertook to write two constitutions: one for Poland and one for Corsica, at the invitation of those states. Poland was partitioned and Corsica was annexed before either constitution could be implemented. In both of these cases, Rousseau was playing the role of the impartial lawgiver who stands outside the law: he was neither Corsican nor Polish, and was giving these people laws without any personal interest or hope for gain.