One of the best pieces on this issue I've read:
"Halloween Orthodoxy and Secular Culture"
By Fr. John Moses
Nov 1, 2008, 10:00
I am not competent to address the spiritual issues raised in this article, but the parts of the article claiming to give the history of Halloween are just plain silly.
Please note that I do not label my statements rebuttals but counter-claims. A rebuttal would require source citation, which I cannot afford to do, since I live a long ways from a proper library.
Claim 1. "The feast of Halloween began among the Celtic peoples of Britain, Ireland, and northern France."
Counter-claim 1. The feast of Halloween takes its origins from the dedication of a chapel in St. Peter's which was specially dedicated to ALL SAINTS. The dedication date of that chapel was 1 November (8th century, year unknown). Pope Gregory transferred the older feast of all martyrs from 13 May 609/610, which had been established by the dedication of the Pantheon by Pope Boniface IV. It boggles my mind that Pope Gregory would have known or cared that 1 November was Samhein among the Picts in the sticks.
Claim 2. "These pagan peoples believed that physical life was born from death."
Counter-claim 2. Maybe they did, but the Druids never wrote down what they believed, so we are not free to speculate.
Claim 3. Therefore, they celebrated the beginning of the "new year" in the fall (on the eve of October 31 and into the day of November 1), when they believed, the season of cold, darkness, decay and death began.
Counter-claim 3. Most people in the northern hemisphere do believe that cold, darkness, decay and death begin in the fall. It's the time when things die.
Claim 4. The Celts believed that a certain deity, whom they called Samhain, was the Lord of Death. To him they gave honor at their New Year's festival.
Counter-claim 4. This is sheer nonsense. Scholars are not in agreement with what Samhein means--beyond the reference to a minor hero whose magical cow was stolen--but there is no Lord of the Dead if you look for him beyond Chick publications or Internet resources.
Claim 5. Many beliefs and practices were associated with this feast, which have endured to this current time.
Counter-claim 5. The efforts of people to debunk Halloween and Christmas by connecting them with ancient pagan practices does not merely race ahead of the evidence, but soars into the the farthest reaches of Internet legend. It takes a great deal of painstaking research to connect even fairly recent customs; the facile assumption that we are doing something just so because the Druids did it one, two or three thousand years ago is arrogant.
Claim 6. On the eve of the New Year's festival, the Druids, who were the priests of the Celtic cult, instructed their people to extinguish all hearth fires and lights. On the evening of the festival they ignited a huge bonfire built from oak branches, which they believed to be sacred.
Non-rebuttal 6. No idea. This could be.
Claim 7. Upon this fire, they offered burnt sacrifices of crops, animals,
Counter-claim 7. Animals were in fact slaughtered and feasted on, if they were judged to be unable to survive the winter on meager rations.
Claim 8. and even human beings
Rebuttal 8. The Druids seem to have performed human sacrifice, if Caesar is to be believed (although he also reported that elk had no joints in their legs, so that the hunter need only saw most of the way through a tree against which his prey was known to sleep standing up; it was a matter of time before the tree fell down and the poor beast, like an unhorsed knight, could not get up and run away), but no evidence gathered by someone hardy enough to gather information beyond the confines of the Internet supports the contention that human sacrifice was specially done on Halloween.
Claim 9. to appease and cajole Samhain, the lord of Death. They also believed that Samhain, being pleased by their faithful offerings, allowed the souls of the dead to return to homes for a festal visit on this day.
Counter-claim 9. This is sheer stuff and nonsense.
Claim 10. This belief led to the ritual practice of wandering about in the dark dressed in costumes indicating ghosts, witches, hobgoblins, fairies and demons.
Counter-claim 10. This is folk-etiology.
Claim 11. The living entered into fellowship and communion with their dead by this ritual act of imitation, through costume and the wandering about in the darkness, even as the souls of the dead were believed to wander.
Counter-claim 11. More folk-etiology.
Claim 12. The dialogue of "trick or treat" is integral to Halloween beliefs and practices. The souls of the dead had--by Celtic tradition--entered into the world of darkness, decay, and death. They bore the affliction of great hunger on their festal visit. This belief brought about the practice of begging as another Celtic ritual imitation of the dead. The implication was that any souls of the dead and their imitators who are not appeased with "treats", i.e. offerings, will provoke the wrath of Samhain, whose angels and servants (the souls and human imitators) could retaliate through a system of "tricks" or curses. One radio commentator takes great fun in calling Halloween, "Begoween."
Rebuttal 12. Loads more folk-etiology.
Claim 13. The sacred fire was the fire of the New Year was taken home to rekindle lights and hearth fires.
Counter-claim 13. This sounds more like the ROman custom.
Claim 14. This developed into the practice of the Jack O Lantern (in the U.S.A.; a pumpkin, in older days other vegetables were used), which was carved in imitation of the dead and used to convey the new light and fire to the home, where the lantern was left burning throughout the night.
Counter-claim 14. Even more folk-etiology.
Claim 15. Divination was also part of this ancient Celtic festival. After the fire had died out the Druids examined the remains of the main sacrifices, hoping to foretell the coming year's events.
Counter-claim 15. Divination was important in pagan society. I would not be surprised if the Irish used Samhein the way that the English used Christmas--to tell the future.
Claim 16. The Halloween festival was the proper night for sorcery, fortune telling, divination, games of chance, and Satan worship and witchcraft in the later Middle Ages.
Counter-claim 16. Not that I can tell.
Let me sum things up.
It is fun and easy to demonize things; it is very hard to do the kind of research necessary to support extravagant theses. Most opponents of Halloween simply cite Internet sources; they do not go to a nice research library and do the incredibly hard work of finding evidence that is generally acceptable and piecing it together convincingly. I have never known any opponent of Halloween refer to the standard sources of history, archeology or linguistics. Nor will I ever, since the instant such an opponent turns to the cold, indifferent facts of history for support, he will be thrust back like a rejected suitor. The assumption seems to be that by being on the side of the angels, one need not play by the rules. I do not accept this. If I am on the side of the angels, playing by the rules is all that matters; my shoddy scholarship or appeal to ignorance will discredit the angels if I do not play by the rules.