Implied Mechanics

While there is remarkably little solid information on how magic works, I think we can make some reliable inferences.

What makes magic dark?

We can of course safely conclude that the characters in the book have unreliable opinions on what is and is not dark magic. This series abounds in examples of unreliable narrators. So what does make magic dark? The crucial clue, I believe, comes in two pieces. First in book four, when the fake Professor Moody is explaining that a class of fourth year students would be unable to successfully cast The Killing Curse.¹ Second, in book five, when Bellatrix explains that Harry must truly intend the Cruciatus Curse.²

The common thread in these two passages is the mental state of the person casting. Intent to harm is a key aspect of dark magic. But I can fully intend to harm with a levitation spell, when I levitate a rock to drop it on someone’s head. The levitation spell is not, however, dark in one situation and light in another. So we need something more, and the first passage gives us this clue. What do these fourth year students lack? They can certainly intend harm. I suspect that the crucial missing ingredient is that while they intend harm, at this stage most of them still cannot see a thestral. Their intent will be flawed, unfocused due to lack of real understanding of the effect they wish to cause.

So again, let us go back to our comparison. With the levitation spell, the student intends to raise the stone. The student wants the stone raised because the student also intends to harm someone with that stone. But their immediate goal is “the stone needs to go up.” They understand this. They want this to happen (for nefarious reasons). They have the magic to make this happen. They trigger the magic. The stone goes up. But raising a stone is not dark. The secondary effect, that it will be dropped, after it is raised, does not matter. The Killing Curse, on the other hand, the student needs to, as an immediate goal, desire to end a life. The Cruciatus Curse requires that the student desire to cause immense pain. Not to desire justice (the spell might partially work), or to shock a person the way a defibrillator might (I doubt the spell would work at all, because the intent is to save a life) but to simply hurt the person just to hurt them. This is why these spells are so evil. This is what makes magic dark.

We now have a definition. Dark magic is that which, as a primary goal, not as a secondary effect, intends a harm on another person. From this definition we can further classify how dark magic is. Is lasting harm intended? Is grave harm intended? Is the person intended to recover from this harm? If the person is intended to recover, will recover happen automatically with time (how much?), or only with the application of magic specifically designed to reverse the effects? Is the magic intended to be fatal, but someone has managed to figure out a way to save some or all people despite the caster’s intent?

By answering these questions, we can begin to derivatively arrive at understandings of why some spells are classified as a jinx, others as a hex, and still others as a curse. We can further grasp why these categories blur, and spells occasionally get miscategorised. One can easily envision that on first encountering a dark spell, one might not appreciate how fatal it can be, oor conversely over estimate its lethality based on small sample size and poorly understood contributing factors. Maybe a spell is not usually fatal, but is, if combined with certain preconditions.³

Light magic

The books do not talk about light magic as such. However, if there is dark magic, there should be light magic. More, we can identify a few spells that would necessarily qualify as such. In creating the Patronus charm, Mrs. Rowling seems to have gone out of her way to classify something as light magic without actually defining this term. The story of Raczidian, while debatably canonical, emphasizes this, punishing the dark wizard for the attempt to use a “good” (aka “light”) spell.

If dark magic is defined by its inherent intent to harm, light magic must be defined by its inherent intent to not harm. Again though, we need to qualify this. The levitation spell was used earlier with an intent to harm, but it can also be used without that intent. I can use a levitation spell with an intent to save. I might levitate a person out of harm’s way. If for whatever reason I cannot levitate the person directly, I might levitate something to catch, pull, or carry the person out of harm’s way. I might intend all sorts of direct good to someone with my levitation spell. But just as it was not dark magic, it will not be light magic. It is not enough that my intent lacks harm, my intent must inherently oppose harm.

What then would qualify? A shield charm might qualify. The shield charm protects the person(s) behind it from harm, and your intent in casting it is to directly oppose the harm intended by the magic you are interposing the shield between. In some fan fiction works, we have however seen reflective shields, that bounce the spell back at the caster. Then my intent is not so pure. I do not only want to interpose protection between a person or persons and harm, I also want to redirect that harm. That reflective shield then would not be “light” magic, it might even be dark.

A healing charm might qualify. The healing charm intends to remove harm. The healing magic might cause harm as a secondary effect, for example, Harry occasionally reports that healing potions are unpleasant to swallow (minor, sometimes trivial harms not intended, but accepted to achieve much higher order benefits). The intent however is key. The primary, both in the sense that it is the most significant, and in the sense that it is most directly intended, effect of the magic is to remove harm from the recipient.

I think from this we can understand the difficulty of the Patronus. It can drive off a dementor, but it is essentially a shield. Designed essentially as light magic, it cannot intend harm, even to a being so foul as the dementor. That it is intensely unpleasant to them is effectively an unintended side effect of protecting the person near them from the dementor’s soul draining effects.

Conclusion

From this we’ve derived three categories of magic. Dark, light, and neutral magic. The bulk of magic is neutral, it can be used for good or for ill depending on circumstances. [Levitation spells], enlarging spells, turning something to stone all end up in this neutral category. In fact, the bulk of magic probably does, even though we have more named examples of dark magic across the series.

But more, we’ve set up a situation where while magic is light, dark, or neutral, society has a very different, far more fluid definition of what constitutes “acceptable” magic, and conflates “unacceptable” with dark and “acceptable” with “light”. This disjunct will necessarily cause a great deal of confusion and any number of problems. Nearly everyone is, to some extent, acting hypocritically, using magic they condemn in others. It also becomes easy to label anything as dark simply because it is convenient to restrict it.