The author of a substantial body of work, the former Oratorian Jean- Baptiste Isoard de Lisme, better known as Delisle de Sales, made famous in 1770 by his Essai pour la morale ou De la Philosophie de la nature, is considered an "heir to the Enlightenment." Yet having failed to remain innovative, he gradually became a marginalized and isolated figure in the learned France of the early nineteenth century. By focusing on publications fromtheRevolutionary and Imperial periods, the aimof this article is to examine the relationships Delisle de Sales weaves between the system of interpretation of the natural world he constructed and the political positions he adopted. The purpose here is to understand more fully the reasons for his isolation and the anachronistic inclinations of a personage, whose epistemological and political choices distanced him as much from the Ideologues as from Catholic theorists. Despite the complex nature of his work, Delisle de Sales proposed an original scientific, social and political project.