J.-J. Rousseau is one of the most interesting and suggestive political thinkers in our modern history. The essay dedicated to him by Bertrand de Jouvenel was first published in France in 1978 and Today it is considered one of the reference texts on the thought of the Genevan. This edition is the first translation published in Spanish of this important text. The Moral State raised by Rousseau is a rationalist response to the great division between the religious and the political from which the Modern State is born. Jouvenel reviews Rousseau the theologian, reformer and politician to return to the contradiction inherent in the Social State. At the same time, he takes up again the question about the moral nature of politics, its pedagogical function and the political vocation of man, offering us current criteria to judge the political reality of today.