I've been reading Rousseau's The Social Contract. First of all, in only a few pages, it is clear that Rousseau is a brilliant political thinker. Right away, he knows to whom he's talking -- Hobbes and Locke. And he shows why the theories of the social contract presented by the two of them cannot be quite right -- very successfully, I think.
His argument against being able to voluntarily place oneself in slavery is wonderful. To be a slave means to cease being a moral agent -- if the master says, "Eat those schoolchildren," the slave is obliged to do it. But this is impossible -- the slave's moral agency cannot be alienated, no matter how much he wants to do so. I believe Rousseau is right. Libertarians should not interfere with "voluntary slavery contracts," but they should treat them as nonsense -- as if you agreed to sell me "all of the galaxies that will never be reached by humans." Two people can clown around and claim they have this agreement, but no one else should help them enforce it, or even allow them to enforce it violently.
For someone who I have often seen presented as "the anti-libertarian," Rousseau has two positions that are largely libertarian:
1) One of the major selling opints of the State for Rousseau is that it serves to secure private property. (Whether he is right that it can do so is doubtful, IMHO, but if it could that would be a good thing.)
2) He makes it clear that only unanimous consent can justify the State, and there is no justification for the, "Your ancestors were conquered, now shut up and obey," explanation of legitimacy put forward by conservatives.
More to come.