The figure of the legislator is one of the most controversial elements of Rousseau's entire political system. It is a symptom of difficulties: safeguard the contents of the social pact from possible degeneration and ensure that the general will can be translated into effective criteria for the decisions of citizens, who are called upon to be their own legislators. In this paper, it is hypothesized that the legislator is called upon to carry out a work of transformation of mankind that finds its profound reason in the failure to develop sociability in human beings. For this purpose, an analysis of Rousseau's anthropology is indispensable. Furthermore, it is necessary to dwell on Rousseau's constant criticism of the Enlightenment. The issue reveals some peculiar profiles of Rousseau's thought such as, not least, a latent disillusionment.