Jean-Jacques Rousseau was fairly prolific, and his works rank among the most widely-read and important in the mid-eighteenth century Enlightenment.
Rousseau's two most widely-read works were Emile and Julie, or Heloise. Both of these books were novels, but were also, in particular Emile, didactic in the sense that Rousseau used them to advance his philosophy that emphasized the cultivation of virtue and the corrupting influence of society. This same theme is found in Discourse on the Origins of Inequality, a philosophical treatise which traces the origins of human inequality (and indeed all human misery) to the emergence of society and civilization. His most enduring work has been The Social Contract, which sought to balance individual liberty with the powers of the state. Rousseau famously argued that no government not founded on the "general will" was legitimate, but he also implied that the state ought to take an active role in the promotion of virtue and patriotism. These ideas would find acceptance among the radical Jacobins in the French Revolution, who regarded Rousseau as something of a patron saint. His Confessions, an autobiography that detailed his own development as a thinker (along with some rather frank details about his life) was his final major work.