[adapted from The Spirits Around Us]:
Note that Christ mentioned both demons and ghosts, which one can also call “revenants.”
Let’s look at those mentions.
“When the disciples saw him walking on the lake, they were terrified. ‘It’s a ghost,’ they said, and cried out in fear (Matthew 14:16).
“They were startled and frightened, thinking they saw a ghost,” was the way Luke 24:37 put it.
“Look at My hands and my feet. It is I myself! Touch me and see; a ghost does not have flesh and bones, as you see I have,” said Jesus (Matthew 24:39).
He would not have mentioned “ghost” if ghosts did not exist and His disciples would not have feared such entities if they didn’t think such entities could cause damage.
If you want to get more explicit, look to Isaiah 19:3, where it says, “Then the spirit of the Egyptians will be demoralized within them; and I will confound their strategy, so that they will resort to idols and ghosts of the dead and to mediums and spiritists.”
The Bible strongly indicates that ghosts (see King Saul) are real but also—as I have stressed— that we are not to initiate contact with them.
Noted an eminent Church scholar named Sir Shane Leslie long ago, “The Church forbids the dead to be evoked, but there is nothing to forbid the dead making the gesture themselves, since it is clear that only by Divine permission could they do so. Whether ghosts are miracles or not, Saint Thomas Aquinas accepts the apparition of the dead which he attributes to the special dispensation of God or else to the operation of spirits, good or bad.”
Saint Gennadius once rebuked a specter that addressed him.
St. Eulogius of Alexandria saw a wraith.
Saint Amatus appeared after his death to his mother.
Saint Gregory tells of a deacon who haunted certain baths (and was seen by a bishop).
It is in his Dialogues.
In fact, many cardinals, bishops, priests, and nuns have been witness to apparitions or other “ghostly” happenings. By the year 1000, says another, Andrew Coynes, “stories of restless spirits of the departed, of ghostly violations of the traditional boundaries between the living and the dead, began to be recorded even by eminent churchmen.”
The Church requires “no motion of faith for or against ghosts,” is the way Sir Leslie (a consultant to Pope Pius XI) put it. In City of God (Book XXII), Saint Augustine mentions a haunted house—whether by an earthbound spirit or a demon, we cannot know—although an exorcism was performed, and perhaps there was no distinction for Augustine between the demonic and the earthbound (for elsewhere he seems skeptical of ghosts).
In the early Church, they were referred to as revenants, and there has been an explosion of reports in our own time. “I don’t know if I built my home on haunted property ten years ago, or if I am being visited by the holy souls,” a woman named Dee Dee from Michigan wrote. “I only know that many nights when I lay in bed to read before falling asleep, I have encountered knocking on my wall above my bed in several places and that it does not cease until I pray. One night I was so unnerved that I pulled my Scapular out of my nightgown, made the Sign of the Cross, and kissed it. The knocking stopped right away. It’s almost as if they were saying, ‘can you put in a few good words for me?’ While the sudden noises, occasional shadows, and missing objects at times startle me, I just say aloud, ‘I will pray for you.’ I believe that’s the best way to handle a haunting. These souls are still on their journey and we must help them any way we can. I am very devoted to the Holy Souls.” [scroll for more]
Many such souls, it seems, are purgatorial. “In August of 2000 my dad passed away from lung cancer in Edmonton, Canada,” wrote an engineering technologist named Waldo W. Ponce. “A few days later he came to me in a dream. He looked younger but serious and he was wearing a long white robe and said to me in Spanish, ‘Tell [my brother] Ivan that purgatory exists. I was there for sixty-three days.’ He then disappeared.
The following morning for some reason I looked at a calendar first thing and counted sixty-three days from the death of my father and it ended on my brother Ivan’s birthday.”
Our prayers for them work—freeing them to Heaven.”
[see below for video of priest explaining ghosts and demons]
[resources: The Spirits Around Us]