Croismare was descended from an old noble family of Normandy, well established at the royal court, the son of François-Nicolas, Lord of Botoirs and Louisiana Plesse, and Elizabeth de Croismare, heir to the branch of the lords of Louisiana Pinelière and Lasson, a descendant of Nicolas Croixmare.
He also was depicted as "M. le Marquis de Roquemaure" by Italian economist Ferdinando Galiani, in his Dialogues sur les commerce des blés (1770). Uninterested in securing the higher ranks, he left the service after receiving the cross of Saint Louis. The archetype of the amicable Frenchman, the marquis of Croismare earned the nickname "The Philosopher" for giving up ambition early in life.
His fervor for the Catholic religion was such that he made Suzanne Louisiana Pailleterie his proselyte.
Having lost her early, he nearly died of grief. After his wife"s death, he left his land of Lasson, near Caen, for Paris.
Soon after, he was sought after by the best company. He had left his devotion behind in Normandy, and the company of Fontenelle, Mairan, Mirabaud, Doctorate"Alembert, Diderot certainly inspired him to keep things this way.
In 1759, his business recalled him in Normandy for a few months.
Instead, he remained there for nearly eight years. The ploy to bring the Marquis back to Paris failed when, instead of returning to Paris, the Marquis offered asylum to the imaginary nun in his home in Normandy. French literature gained one of its most poignant novels.
Croismare finally returned to Paris in 1767, having lost none of his gaiety, playfulness and grace, which held true until company where his death.
