UNDERSTANDING HOW DEMONS ACT UPON THE HUMAN PERSON
When looking at how Catholic demonologists, exorcists, and deliverance ministers speak of how a demon acts upon a human, one will often hear the preposition “IN" used. Similarly, even when Christ exorcised possessed people in the Gospels we read that he commanded the Demons to, “Come OUT." If a demon is INSIDE of a human being, and is commanded to come out, does this mean that he occupies a particular space - literally - inside that person? Actually, we believe this is a rather complicated area to explain.
In the strictest sense, an Angel as well as a Demon (who of course is a fallen angel), does not occupy space and time as we have said in other sections of this website. We believe, from the teachings of St. Thomas Aquinas, that the demon ACTS UPON THE PERSON in certain real ways. However, it is also true that in a very real sense - he is indeed “inside" the person in the case of possession, just not in a literal, physical sense; as though if one were to surgically operate on a human being who is possessed, he might locate the demon in the person's colon! It is not accurate to think of this in that way. Yet, it remains that it is accurate to say that the demon is INSIDE the person and must be ordered - or exorcised OUT of him or her. Thus, the demon does “enter" a human, as we read in the Gospel account of the Passover: “Then Satan ENTERED into Judas called Iscariot, who was of the number of the twelve..." (Luke 22:3). In an attempt to avoid this confusion this is why you will hear exorcists and demonologists use the term ATTACHMENT to describe this Demonic presence. It is a term most people today can understand.
Remember that humans are both visible (physical) and invisible (soul and spirit). A demon, who is a pure spirit by nature, acts upon the physical aspect of the human in a tangible but spiritual way during possession and other forms of extraordinary demonic influence (also known as DEMONIZATION - literally: “to have a demon" ).
Some experts believe that the demon can “enter" the Human through their eyes, or through the nape of the back of the neck - which is a crucial part of humans' central nervous system where the brain stem meets the spinal cord. Even though the Demon may enter by way of a specific area or feature of the body, he still in the strictest sense is ACTING UPON upon that human's locomotive aspects in the cases of possession.
Ecce crucem Domini. Fugite, partes adversae.
Vincit Leo de tribu Juda.
(Behold the Cross of the Lord. Let the enemy flee.
The Lion of the tribe of Judah conquers.)