The aim of this paper is to study the contribution of Jean-Jacques Rousseau's works to the sociological analysis of social coordination, i.e., how people succeed in organizing themselves to act in concert. Rousseau focuses his attention on mankind, and more precisely the human being as shaped by nature and the human being as part of society. He tries to understand what motivates him to act, or could make him act. However, to this theoretical position, which is the precursor to later developments in the sociology of action, he adds an essential proposition: social coordination can only take place on an infra-rational base which binds people by means of feelings of sociability. Although natural, these loving passions are by no means spontaneous. They must be sustained and protected by some devices that embody the symbolic mediation between men. Thus with a view to proving that the unity of society is rooted in the "heart," apart from any calculated interest, Rousseau studied the dimension of human existence that is social belonging. In this connection he formulated a complex set of hypotheses and analyses in order to transcend the most firmly rooted dualisms: nature versus culture, individual versus society, being versus appearance, and reason versus passion. Rousseau attempted to construct a kind of synthesis between what the nature of man as a free being demands and what his condition as a social being requires. This analysis opens the way to a "structural individualism" in sociology, i.e., a theoretical approach that is attentive to the individual, to his autonomy and his motives as much as to the infra-rational social and symbolic conditions of his cognitive activity and actions.