Chapter XVIII.—This Power in Proportion to Faith.
“There is therefore a measure of faith, which, if it be perfect, drives the demon perfectly from the soul; but if it has any defect, something on the part of the demon still remains in the portion of infidelity; and it is the greatest difficulty for the soul to understand when or how, whether fully or less fully, the demon has been expelled from it. For if he remains in any quarter, when he gets an opportunity, he suggests thoughts to mens hearts; and they, not knowing whence they come, believe the suggestions of the demons, as if they were the perceptions of their own souls. Thus they suggest to some to follow pleasure by occasion of bodily necessity; they excuse the passionateness of others by excess of gall; they colour over the madness of others by the vehemence of melancholy; and even extenuate the folly of some as the result of abundance of phlegm. But even if this were so, still none of these could be hurtful to the body, except from the excess of meats and drinks; because, when these are taken in excessive quantities, their abundance, which the natural warmth is not sufficient to digest, curdles into a sort of poison, and it, flowing through the bowels and all the veins like a common sewer, renders the motions of the body unhealthy and base. Wherefore moderation is to be attained in all things, that neither may place be given to demons, nor the soul, being possessed by them, be delivered along with them to be tormented in eternal fires.