Harry Potter is a complicated thing.
The abilities people are born with in the Harry Potter world do not fit either the Biblical or even most modern New-age definitions of magic. At best, they could be called metaphysical talents.
The people of Potter's world are born with their abilities, apparently after the same fashion that allows some people to be born extremely athletic or with a spectacular singing voice or perfect pitch. The gift is neutral at birth, gaining strength only from within the individual and needing no outside demonic force to fuel it. In short, if God Himself decided to have some people be born on earth with certain "magical" abilities, the default you would get would be the "magical" children of the Potter world.
Putting these abilities into the realm of simple gifts one happens to be born with, we are then left with the "what you do with it determines the good or evil of it" philosophy. So you see great and powerful -- but also very moral -- "wizards" like Dumbledore, who teach that there is no greater power than to lay down one's life for a friend/family member, and that Love conquors all, etc.
But you also see the wicked members of this gifted segment of the population. People like Wormwood and Voldemort who are willing to engage in wicked practices and even demonic activity to unnaturally develop their abilities beyond what is right, proper, or good.
In this world, "magic" becomes a wholly natural and God-given ability that anyone may be born with, whether they want such a gift or not. This ability can be used faithfully and with godly restraint...like a strong man who uses the physical prowess God gave him at birth to protect and serve his community as a well skilled police officer. Or this ability can be twisted into wickedness and evil -- like if the same strong man decided to use steroids and shady contracts with corrupt judges to rig the Olympics.
In general (but not in specifics) the magical lessons taught at Hogwarts become then similar to the martial arts. They aren't good or evil per se, but they could certainly be used in both good or evil ways. Chemists may synthesize medicines or poisons, too.
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Having said all that, the author uses the words "witch" and "warlock" to describe these people of metaphysical ability. This is a terrible shame.
The latter term is rediculous in any context because it has roots in an older word which is Scotch Gaelic for "traitor."
The former term is 1. inaccurate and 2. evil in nature.
A witch is a person who starts out as normal as anyone else. This person sells him or herself into a contract of Evil with demonic forces to obtain special powers. While the powers may seem benign on the surface (healing, prophecy, etc), they are evil in form -- because thier source is other than the Holy Spirit. In effect, a "witch" is a thief who has stolen abilities that should be granted only to those anointed by the Spirit to do the work of the Lord. The exact mechanics of why God ever allowed such contracts to be made and why demons could give such powers to mortals is a topic beyond the scope of this post...suffice to say it's one of many proofs for the doctrine of Free Will, for both humanity and fallen angels.
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One place where the books of Harry Potter founder into danger is in the area of divination. The Bible specifically teaches that one should not, in any circumstances, practice divination.
The only way godly people may receive knowledge of future events is to either pray to the Lord directly for wisdom in such matters, or to go to a prophet of God. Doing divination rituals where you seem to be reaching out into the universe for answers from anyone -- or anything -- that may provide them is forbidden, and actual prophets in these days are extremely rare (but I won't discount the chance that there may well be some - as many end-time Biblical verses say we shall see a rise in prophets as we get closer to the last days).
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I have always regretted that there wasn't more in the pages of Harry Potter to depict the religious leanings of the characters. Dumbledore's speeches on the power behind one who lays down his life for his friends, and on the nature of Love, would seem to be almost Biblical in origin. Harry's parents are buried in apparently consecrated graves in a church yard. That doesn't mean they were saved, but it *might* allude to the idea that they were believers. Potter's aunt and uncle were clearly secularists who, if they bothered to even attend a church, did it for appearances only.
So...do you prohibit the fiction of Potter's world because it uses words like "magic," and "witch" and "warlock" .. or do you allow the books and explain to your children the differences between the "traditional" wicked witch of Biblical teaching and the poorly named "witches" of Potter's reality?
That is a question that will only be answered after each individual parent Goes to God in prayer -- and the answer may not be the same for everyone.
For my part, I enjoyed the books. They reminded me a little bit of the worlds of C.S. Lewis which also contained magic but which (because Lewis was doing it on purpose) made a much easier link to follow between fictional fable and Biblical truth. But I know some households which have avoided the books entirely and if you feel you need to do that, then that is probably what you should do.
Janette