Catholics believe in communicating with the dead: we call it prayer. We ask the saints for their intercession, and we pray for the souls in purgatory. These are good practices to have in our daily prayer life, with special emphasis given on All Saints’ Day and All Souls’ Day.
Where do ghosts fit with Catholic teaching, and where does Halloween fit with Catholic practice? The two questions are not necessarily related, but in the USA they are both part of Halloween, so we can address them together.
The Merriam-Webster online dictionary gives the following as its first definition of ghost: “the seat of life or intelligence: soul.” This helps to explain why the Third Person of the Trinity is sometimes called the Holy Ghost; it may sound strange to some in the twenty-first century, but its linguistic roots make sense.
In any case, the second definition from that dictionary is what interests us for Halloween: “a disembodied soul, especially the soul of a dead person believed to be an inhabitant of the unseen world or to appear to the living in bodily likeness.” This is what is usually meant by the word ghost in our culture: the soul of a deceased person, operating in our physical world, in bodily likeness but without a living human body. I would expand that to include the idea of such a being operating invisibly, but having physical powers such as causing objects to move, making sounds (including voices), and disrupting electronics.
When we say that a human being has died, we mean only the body. The soul goes before Jesus for particular judgment, learning whether he will go to hell or heaven, or purgatory before heaven. When Jesus returns for the General Judgment at the end of the world, he will raise everyone’s body from the dead, to join the soul for eternal misery in hell or eternal happiness in heaven. Until then, human beings (almost all of them) are disembodied souls, so they do fit that part of the definition of a ghost. They do not, however, have any inherent physical appearance: just as our souls are not visible while our bodies are alive, neither are they visible after our bodies are deceased. Having said that, God can make exceptions and have deceased human beings appear as he wills.
Which of the three places—hell, heaven, or purgatory—would a soul come from, to do ghostly activity on earth? Certainly not from heaven: if God has a saint appear or speak to someone on earth, it is to give a clear message or to give inspiration, not to cause vague and pointless sights, sounds, or moving objects. The same is true of souls in purgatory: if they appear or speak to someone on earth, as has occasionally been reported, it is to give a message, ask for prayers, or give a warning about the sufferings therein.
This leaves the souls in hell. Could they return to earth to do evil, or at least to frighten and lead people astray? This seems to contradict the doctrine that the souls of the damned are in hell for eternity, without getting breaks to return to earth. Though some saints have had visions of hell, in Church teaching and tradition we do not find that particular human souls from hell return and act in this world. The Catholic Rite of Exorcism even warns the exorcist to beware that the devil might purport to be the soul of a deceased person.
That brings us to the angels: could what we call ghosts be good angels or demons? The short answer is no: the angels never had bodies to begin with, they certainly were never human, and so they are not disembodied souls of dead persons.
Angels do have the ability to take on a kind of appearance. St. Thomas Aquinas speculated that they do this by manipulating the air—something like a cloud. Though their appearance could be frightening, as when the angel appeared to the shepherds at Christmas, good angels would not appear for the sole purpose of frightening people. Nor would they randomly or pointlessly move objects, make sounds, or flicker lights.
On the other hand, fallen angels or demons might do any of these things. We should not be surprised if people looking for ghosts are, on some occasions, being fooled by demons. Demons might tempt these people to devote attention to pointless spiritual practices such as ghost hunting, or destructive spiritual practices such as communicating with the dead using boards, cards, or alleged psychic powers. In conclusion, in the rare cases where unnatural activity occurs that people attribute to ghosts, it could be the work of demons.
And now for Halloween: is it sinful to celebrate? This depends on what a person is doing. Some sinful practices have already been named, such as using cards or Ouija boards to communicate with the dead. Using devices to attempt to detect sounds or electrical impulses of disembodied souls seems to be the same, since they are still attempts at communication with the dead. Witchcraft, spells, curses, and other spiritual activities unconnected with God and his angels and saints are likewise sinful.
In a different category are the American customs common at Halloween. Wearing a costume is not sinful, putting plastic skeletons or fake tombstones or inflatable ghosts in one’s yard is not sinful, and trying to get a bagful of free candy is not sinful. The practice of dressing up as a saint is certainly commendable, and dressing as a murderer from a horror movie is certainly appalling. But we should not confuse wearing a costume of a witch or devil or ghost with false worship or false beliefs, any more than we equate dressing as a pirate with the desire to assault and pillage coastal villages. It’s all right to have a happy Halloween.
More importantly, have a blessed Feast of All Saints and Feast of All Souls.