Question Two of Chapter Three of the Third Decade
Whether a demon can enter the whole body or some part of it
It is asked whether demons, when they enter bodies, enter the whole body or some part of the body, such as a finger or the muscles.
To this little question, on account of what was said immediately above in reply to the first argument, some say that when, with God permitting, a demon enters the bodies of human beings by besieging them, it does not enter the body of the animal or any part of it, such as a finger or a muscle.
For in that case two created spirits would be in the same place, which in the common course of things—as they say, and rightly—cannot be. For neither two good angels, nor two evil angels, nor a human spirit and the devil can coexist exactly in the same space or site.
Rather, a demon is said to enter some inanimate humor in a human being or in another animal, whether blood, bile, urine, or the dregs of the entrails.
But if it is said against these persons, “How can a spirit which does not coexist with the body, organs, or muscles of an animal supply or exercise the local motions of the organs or parts within the body?”, it is answered that one can conceive in two ways that a spirit can move a body to which it is not united informatively.
In one way, this occurs through the motion in itself and in its own right of the spirit which is joined or adheres firmly to the corporeal movable thing through some species of union.
For example, if the human spirit or soul, while its union with the body persisted, were moved in itself, the body would also have to follow it. This would occur by reason of the soul’s informative union with the body, as perhaps will occur in the motions of glorified bodies.
The second manner of conceiving how a spirit moves a body is toward local motion through an intrinsic action of its own, by apprehension from the command of the will.
Therefore, just as the human spirit immediately and in itself moves certain parts of the body locally toward an intrinsic action of its own through apprehension and the consequent free will, at the command of the will, so also good and evil spirits themselves can move the body and its parts immediately at the command of their wills, so that the spirit coexists there locally, as they do when they enter some humor in a human being, as was said above.
Whatever may be the case concerning several evil spirits or several good spirits, or concerning a good and an evil spirit in the same animate or rational body, nevertheless there ought to be no doubt that many evil spirits can enter one human body simultaneously.
This is evident in Mark, chapter 5, concerning the demon who was called Legion; concerning the malignant spirit with the brute spirit in the serpent, of which Scripture says in Genesis, chapter 3, “But the serpent was more cunning,” and so forth; and concerning the good spirit with a brute spirit as is evident in Balaam’s ass.
These things are from Henry of Assia upon Genesis.