Symptoms of Demon Infestation
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 men’s 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.
— Recognitions of Clement IV.XVIII. ANF08
The Authority of Christians Over Demons
Is it, then, that we are of another and a superior nature, and that therefore the demons are afraid of us? Nay, we are of one and the same nature with you, but we differ in religion. But if you will also be like us, we do not grudge it, but rather we exhort you, and wish you to be assured, that when the same faith and religion and innocence of life shall be in you that is in us, you will have equal and the same power and virtue against demons, through God rewarding your faith. For as he who has soldiers under him, although he may be inferior, and they superior to him in strength, yet ‘says to this one, Go, and he goeth; and to another, Come, and he cometh; and to another, Do this, and he doeth it; and this he is able to do, not by his own power, but by the fear of Cæsar; so every faithful one commands the demons, although they seem to be much stronger than men, and that not by means of his own power, but by means of the power of God, who has put them in subjection. For even that which we have just spoken of, that Cæsar is held in awe by all soldiers, and in every camp, and in his whole kingdom, though he is but one man, and perhaps feeble in respect of bodily strength, this is not effected but by the power of God, who inspires all with fear, that they may be subject to one.
— Recognitions of Clement IV.XXXIII. ANF08