The book “Histoire de la magie en France; depuis le commencement de la monarchie jusqu’à nos jours;” (‘History of magic in France; from the beginning of the monarchy until today’) by Jules Garinet (1797-1877), was published in 1818 in Paris by Foulon.
Around the year 250 Saint Dénis (Dionysius) began to preach to the Gauls. Those christianised Gauls believed, that the souls leave the bodies of the dead to torment the living.
Bollandus wrote about Saint Germain of Auxerre (378-448), that he exorcised a lot of demons. One evening he exorcised ghosts from a tavern, in which the ghosts held dinner every evening. Martin of Tours (331-399) was not only a wellknown exorcist, he was also awaking dead people.
Gregory of Tours (538 -594) wrote in his book “Vie des Pères” about the contemporary saint and poet Venantius Fortunatus (535-605). Venantius Fortunatus came back home from a pilgrimage and found his cell full of demons. He asked them who they were and where they came from. They said they came from Rome the day before. He exorcised them by yelling at them.
The demonographer Pierre Le Loyer (born 1550) wrote in his book “Discours des spectres” (published 1608) about Sulpitius the Pious (570-647). Sulpitius travelled through his diocese, when peasants asked him to exorcise a devil from of a lake. He gave them a vial of chrism (olive oil with perfume). When the peasants threw the flask in the lake, the devil fled back to hell and the lake was suddenly full of fishes. The abundance of fish fed the whole region.
All the French saints of those centuries were exorcists and did lots of miracles. That proves, that the people believed in magic, sorcery and demonic possessions.