Jacques-André Naigeon, a French writer, was an associate of Denis Diderot. Naigeon was not an original thinker; he became an editor, compiler, and commentator after having tried painting and sculpture, but he considered himself a philosopher and was proud of his classical erudition. A bibliophile, too, he accumulated one of the great collections of Greek and Latin classics of his time. Having been accepted into the group of Encyclopedists surrounding Baron d'Holbach, he became an aggressive atheist. He attached himself to Diderot as a disciple and tried to imitate his tone, his manner, and his ideas. Diderot in turn enjoyed Naigeon's wit and tolerated his bad temper, stiffness, and pedantry; Naigeon helped Diderot with the salons and the Encyclopédie. Naigeon later persuaded Diderot to make him his literary executor. He preserved and edited many of Diderot's manuscripts but did...