
By the end of 1830 he was an enthusiastic Roman Catholic, to the consternation of his former admirers. The skepticism of Collin de Plancy increasingly subsided over time. Theologians should leave to the poets the depiction of Hell, and not themselves seek to frighten minds with hideous paintings and appalling books".

All the catalogues made herebefore are only the fruit of a more or less disordered imagination. But only God could know the punishments meted out to the guilty, or the place that holds them. For example, the book reassures its contemporaries as to the torments of Hell: "To deny that there are sorrows and rewards after death is to deny the existence of God since God exists, it must be necessarily so. Influenced by Voltaire, Collin de Plancy initially did not believe in superstition.

It's lists several demons, deities and spirits from different cultures. Dictionnaire Infernal ("Infernal Dictionary") is a book on demonology, written by Jacques Collin de Plancy and illustrated by Louis Le Breton.
