slavery
Again as in On Social Contract(Book I, Chap. 4, "On Slavery") Rousseau next considers the question of whether voluntary slavery could be the basis for legitimate rule, as both Hobbes and Grotius had claimed. Could an individual, or a whole people, agree to submit themselves or "alienate" themselves for life to a master?
Rousseau suggests that the very posing of the question brings forth the absurdity of the claim, for to renounce one's liberty is to renounce one's life, and that no man has a natural right to do.
Rousseau argues (in para1644) that if there were any restrictions on such submission, then in fact one would not be dealing with true slavery but with a kind of contract (e.g. indentured servitude).