In January 1758, Rousseau addresses to Sophie d' Houdetot the Letters morals, in which he undertakes to exceed the contradictory opinions of the philosophers to establish his principles on a steadfast certainty.

These elements are taken again and put in order in the Profession of faith of the Savoyard Vicar, that Rousseau includes with book ÌV of the Emile. The Cartesian inspiration of the project, attested at the beginning of the text, should not mask the general orientation of the Profession of faith, which more endeavors to fix a human morals that to found knowledge.

The character of the Vicar, inspired by the abbots Jean-Claude Gaime and Jean-Baptiste Gâtier, expresses this requirement well. Is the Vicar catholic, but “what was I to think when I sometimes heard it approve contrary dogmas with those of the Roman Church and appear to estimate all his ceremonies poorly? I would have believed it protesting disguised, if I had seen it less faithful to these same uses whose it seemed to make case rather little”. All the movement of the Profession of faith is summarized here: it is enough to consult its reason and its heart to discover the elements of the natural religion (i.e. the morals of the man), which Protestantism approaches more than Catholicism.

But each individual must remain in the religion of his fathers, in order not to be satisfied with abstract speculations and to register the religious feeling in a real community. Intended to expose the Christianity of Rousseau, the Profession of faith is directed against the materialists (it is initially about Helvétius) and against the clan of the philosophers, whose skepticism chokes the spontaneous movements of the heart: “The philosophical indifference resembles the peace of the State under the despotism; it is the peace of death; it is more destructive than the war even”.

The Written letters of the mountain, as for them, will criticize especially religious intolerance.