There is no such thing as black magic in the Dresden files, and it is going to be a major plot point later.
Specifically, when I say there is no black magic, I mean that violating the laws of magic does not turn the user evil.
I am sure many of you reading this are thinking I am crazy because so many times in the DF we are told that black magic does this, that the Blackstaff is what keeps McCoy from going insane, that we have seen Harry deal with Warlocks that have gone insane, and that Harry and others can sense the taint of black magic.
Hear me out.
We get our information in the story from Harry, who in turn has gotten his perspective on black magic from the WC, McCoy, etc. But Harry believes two
contradictory things about magic. -He knows that in order to do magic, you have to believe in what you are doing. You have to have conviction in what you are doing with the magic.
-He also believes that people who violate the laws of magic turn evil over time because of it.
The problem with this is that if a person must believe in their magic to do it, than they were already as evil as whatever actions they took with it, by definition. Therefore, it is not black magic that turns a person evil. A person must be evil do do black magic. Therefore magic is as good or evil as any other tool, its being black or not depends entirely upon the use to which it is put.
-We dont really know what the blackstaff does, and we dont critically consider what we are told about it because confirmation bias makes us see what we want. We already think black magic corrupts, so the explanation seems plausible.
-We dont really know that warlocks were driven mad by their black magic. The state of mind of the warlocks is no different from, and entirely consistent with, a person doing evil in general. Its not uncommon for a bad person to get worse over time.
-This is true of every assumed example of black magic corruption in the books. There are no cases of evidence that can not be explained by normal human behavior.
Another thing to consider is that since the behavior of persons violating the laws can be entirely explained by normal human evil doing and psychology, than how could the White Council possibly know its corrupting anyone beyond their own self-corruption.
Epistemologically speaking, they couldn't. And that means they are claiming to know something they could possibly know, because they have no epistemically valid means of knowing it.
Several evidences other indications that black magic does not corrupt the user:
"As for violating the laws of magic themselves turning you good or evil, well.
There’s something to be said on either side of the argument, in the strictest sense, though one side of the argument is definitely less incorrect than the other. But it’s going to take me several more books to lay it out, so there’s no sense in ruining the fun.
"
Jim
Jim would have no reason to have to "lay it out" if the default assumption that Harry tells us from book one, that black magic corrupts, is true.
"I had to consider the possibility that she’d been trying to do the right thing: using her power to help someone in dire need. The thought made me uncomfortable as hell. I knew that the necromancers I’d met were deadly dangerous, and that if I wanted to survive a conflict with them, I would have to be ready to hit them fast and hard and without any doubts. That’s easy when the enemy is a frothing, psychotic monster. But Kumori’s apparently humanitarian act changed things. It made her a person, and people are a hell of a lot harder for me to think about killing. Even worse, if she’d been acting altruistically, it would mean that the dark energy the necromancers seemed to favor might not be something wholly, inherently evil. It had been used to preserve life, just as the magic I knew could be used either to protect or to destroy. I’d always considered the line between black magic and white to be sharp and clear. But if that dark power could be employed in whatever fashion its wielder chose, that made it no different from my own. Dammit. Investigation was supposed to make me certain of what needed to be done. It was not supposed to confuse me even more. When I opened my eyes, thick clouds had covered the sun and painted the whole world in shades of grey."
Jim Butcher. Dead Beat (Kindle Locations 3162-3172). Orbit. Kindle Edition.
I think this entire part of Dead Beat is clear foreshadowing that Harry's view on black magic isn't correct. He is clearly uncomfortable about the idea, and its a weird thing to put in the series if there isnt something to it.
-We know Luccio tells Dresden the laws are really about constraining the power of wizards.
"Note also the killing law only applies to Humans.You can kill as many faeries as you want with magic."
"Bingo. It hardly seems fair, does it?
The Laws of Magic don't necessarily match up to the actual universal guidelines to how the universal power known as "magic" behaves. The consequences for breaking the Laws of Magic don't all come from people wearing grey cloaks.
And none of it necessarily has anything to do with what is Right or Wrong. Which exist. It's finding where they start or stop existing that's the hard part."
Jim
Broadly speaking, I think the WC lies about this deliberately because it is easier to get people to follow the laws if they convince everyone that breaking them will mind fuck them into becoming evil, and because it gives the black magic an "icky" component, and many humans are motivated by disgust based morality. Additionally there is the aspect discussed by Harry about Kumori in Dead Beat. It dehumanizes perceived black mages and makes it easier to enforce the laws. The black staff is just a prop in the lie. They do this because the white council wants to control wizards, and keep the power to do certain things to itself.
Originally, I think this went back to the time of the original Merlin. I think that as far as the story goes this is all going to link together back to when Mab was Human and knew the Merlin. I think that the laws became a thing to try to limit the political influence of wizards after the original Merlin's dealings with King Arthur, and the mess that came from that. I think that whatever happened back then was so bad that the draconian laws of magic were put in place to make sure it never happened again, and that led to the current state of affairs where killing with magic to defend yourself as barely a defense, and things like necromancy go unexplored even though they may have valuable uses.
Furthermore, while I am not sure how this will all add up, I think the fact that Harry's mother was opposed to the laws of magic and that the details of her life are still a mystery is a big indicator that this is going to be a major plot point later. Its one of the only things we know about her, which is that she disagreed with the laws. I don't think information like that was put in the story idly.
But to sum it up I think the laws of magic are a lie and that this is going to be a central feature of the main plot of the series when it gets revealed.