In 1756 Rousseau and Diderot were still close friends, and Rousseau was falling in love with the Countess d'Houdetot. The letters that make up the body of
That Infernal Affair reveal the apparently sudden breakdown of these and other relationships of Rousseau, against a background of the Seven Years' War, the Lisbon earthquake, and the brutal judicial system of the Old Régime in France. Rousseau's break with Diderot represents the watershed separating sentimental attitudes from the rationalism of Enlightenment (embodied in the
Encyclopédie), a break that still colors Western thought. The letters (and the editors' preface, notes, and appendix) reveal not only the «facts» of the case and Rousseau's mental state but also the self-serving manipulation of documentary evidence by unscrupulous erstwhile «friends,» including Madame d'Epinay and her lover, Baron Grimm.