The objective of this text is to show how the figure of the Legislator presented by Rousseau is essential for carrying out the transition movement from the abstract to the concrete in the Social Contract. The occurrence of such a movement is noticeable in different parts of the work, but our focus is to address it right at the beginning, starting from book two. To this end, we deal with the chapters concerning the Legislator, the people and the various systems of legislation: in the chapter on the Legislator, we understand the need for such an individual in Rousseau's theory, as well as his centrality for the consolidation of a legitimate society, such as the principles of political law prescribe; the chapters referring to the people and the different systems of legislation, in turn, allowed us to reflect on the historical circumstances of the people, which must be taken into account by the Legislator, so that he can propose adequate legislation for the people to whom it is intended.