This is the fourth of five volumes of the letters of the French philosopher Claude Adrien Helv?tius (1715-1771), author of the controversial De l'Esprit (1758). Featuring the correspondence of Mme Helv?tius, n?e Anne Catherine de Ligniville (1722-1800), in the years following her husband's death, this volume also includes letters by and to Helv?tius discovered since the publication of the first three volumes.

Mme Helv?tius enjoyed an active widowhood, welcoming to her salon in Auteuil a group of intellectuals who came to be known as the Id?ologues. A close friend of...