Chapter XVI.--Why They Wish to Possess Men.
"Now that the demons are desirous of occupying the bodies of men, this is the reason. They are spirits having their purpose turned to wickedness. Therefore by immoderate eating and drinking, and lust, they urge men on to sin, but only those who entertain the purpose of sinning, who, while they seem simply desirous of satisfying the necessary cravings of nature, give opportunity to the demons to enter into them, because through excess they do not maintain moderation. For as long as the measure of nature is kept, and legitimate moderation is preserved, the mercy of God does not give them liberty to enter into men. But when either the mind falls into impiety, or the body is filled with immoderate meat or drink, then, as if invited by the will and purpose of those who thus neglect themselves, they receive power as against those who have broken the law imposed by God.
Chapter XVII.--The Gospel Gives Power Over Demons.
"You see, then, how important is the acknowledgment of God, and the observance of the divine religion, which not only protects those who believe from the assaults of the demon, but also gives them command over those who rule over others. And therefore it is necessary for you, who are of the Gentiles, to betake yourselves to God, and to keep yourselves from all uncleanness, that the demons may be expelled, and God may dwell in you. And at the same time, by prayers, commit yourselves to God, and call for His aid against the impudence of the demons; for whatever things ye ask, believing, ye shall receive.' [736] But even the demons themselves, in proportion as they see faith grow in a man, in that proportion they depart from him, residing only in that part in which something of infidelity still remains; but from those who believe with full faith, they depart without any delay. For when a soul has come to the faith of God, it obtains the virtue of heavenly water, by which it extinguishes the demon like a spark of fire.
[736] Matt. xxi. 22.
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 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.
Chapter XIX.--Demons Incite to Idolatry.
"There is also another error of the demons, which they suggest to the senses of men, that they should think that those things which they suffer, they suffer from such as are called gods, in order that thereby, offering sacrifices and gifts, as if to propitiate them, they may strengthen the worship of false religion, and avoid us who are interested in their salvation, that they may be freed from error; but this they do, as I have said, not knowing that these things are suggested to them by demons, for fear they should be saved. It is therefore in the power of every one, since man has been made possessed of free-will, whether he shall hear us to life, or the demons to destruction. Also to some, the demons, appearing visibly under various figures, sometimes throw out threats, sometimes promise relief from sufferings, that they may instil into those whom they deceive the opinion of their being gods, and that it may not be known that they are demons. But they are not concealed from us, who know the mysteries of the creation, and for what reason it is permitted to the demons to do those things in the present world; how it is allowed them to transform themselves into what figures they please, and to suggest evil thoughts, and to convey themselves, by means of meats and of drink consecrated to them, into the minds or bodies of those who partake of it, and to concoct vain dreams to further the worship of some idol.