Question Two of Chapter Five of the Third Decade
How, and in how many ways, a demon deludes a human being’s senses
It is asked how, and in how many ways, demons delude the human senses.
Master Bonaventure responds in Book II of the Sentences, distinction 8, saying that demons mock the human senses in three ways.
First, by showing as present what is not present.
Second, by showing a thing otherwise than it is.
Third, by hiding what is present.
They do the first by offering species. They do the second by varying the sense or the object. They do the third by furnishing an impediment.
The first can be understood thus. When phantasms existing within are offered with a powerful presentation to the interior power, or the interior power attends strongly to them, the likeness of a thing then appears to be the truth. This is manifest by nature. For to a frenzied person, because a smoky vapor has risen to the brain from a slight external occasion, it appears that he sees or hears many things which are not present to him.
Likewise, through a strong turning of the attention a phantasm appears to be the truth, as Augustine illustrates in the book On the Trinity: a certain man thought about the image of a certain woman with such concentration that it appeared to him that he coupled carnally with her even while awake. In this manner a demon can make diverse things appear to a human being.
Second, demons can delude the senses by showing a thing otherwise than it is. This can occur naturally because of some variation on the part of the organ, as when a humor of the blood or a fiery vapor descends to the eyes and it appears to a human being that the things outside are red; or because of some variation on the part of the object, as sometimes, through the placement of a candle or the arrangement of pieces of straw, they appear by a natural operation to be serpents.
Something similar occurs through certain powers of some mineral things, as is evident in a mirror of steel and in a concave mirror. Since this mode is not hidden from demons and they are swift ministers, they too can produce such things by illusion.
In the third way, demons can delude the senses by hiding what is present. For a thing which is present can escape our sense in two ways: either because the power of the sense and faculty is impeded from reaching the sensible thing, or because the sensible species is impeded from reaching the sense.
In both ways it can be brought about by the power of a demon that the sense does not perceive what is at hand. Through this power a demon is said to be able to render a human being invisible, although it is certain that he cannot truly do so.
Thus a response is given to the gloss of Rabanus upon Exodus 7, on the passage “Pharaoh’s magicians did,” and so forth: “The magicians deceived the eyes of the spectators by diabolical fictions, so that things remaining in their own species appeared to be other things.”
The same response is given to what is related in the Itinerary of Clement, where Nicetas, narrating Simon’s illusions to Peter, says: “We saw dogs sing and images walk”; to the companions of Ulysses who were turned into beasts by that great and most renowned Circe; to the companions of Diomedes who were turned into birds, concerning whom Book XVIII of The City of God, chapter 16, treats; and to the woman brought to the holy father Macarius who appeared to her husband and to those bringing her to be a mare, but to Macarius to be a woman.
It is said, therefore, that all these things were done by the art of demons. When demons do these things, they do not give a new species or newly remove one. Rather, they present the species which was already in the phantasy so vividly and swiftly to the interior power of the phantasy and imagination that the human being believes he is looking upon a true exterior sensible thing.
But if it is said from the Philosopher that a particular sense does not err concerning its proper object, it is answered that this is true by its nature, provided, however, that the media remain sound—namely, the disposition of the organ, the medium, and the object.
All these things are from the author cited above and Master Johannes de Turrecremata upon the chapter Episcopi, cause 26, question 5.