Snapedom

Also, note that businesses engaging in trade involving dark arts (Borgin and Burkes for example) operate quite openly without apparent fear of legal reprisal. If all dark magic was uniformly understood to be evil magic that is not to be tolerated, this would hardly be the case. People also speak openly of dark magic and the idea of using it. The ministry does not ban all dark magic, it bans the use of certain spells, some of which are also recognized as dark. It also strictly regulates other forms of magic that are never called dark by anyone, but that have the potential for harm. It doesn't state that it bans them for being *dark* specifically, it bans them because their only use is to harm people. Just as some countries ban assault rifles. Whether their harming people is what makes them dark or not is never stated clearly by the text OR by any character, so that would be speculation by the reader. We even see a student from Durmstrang, which teaches the Dark Arts directly, being quite willing to be publicly seen courting a Muggleborn and behaving (when not imperiused of course) as something of a gentleman, possessing normal moral sense. Viktor has learned dark arts, but is never pointed out as being either evil or 'too noble' to use the dark arts, so the two don't necessarily go together. Also, Durmstrang is not reviled by the international magical community for teaching dark arts, but seems fairly respected as an academic institution by a sizeable portion of the international magical community, though not by all. That would hardly be the case if the dark arts were understood to be necessarily evil and harmful within any sort of coherent magical theory. It rather suggests that understanding of what the dark arts are is not in fact uniformly agreed upon at all, which fits with what we see of characters' opinions in the books.

All we know is that a very few spells are uniformly considered dark, but not why; that some spells are considered dark by some characters, but not why; and that some characters, but not all, equate dark magic with evil magic. There is nothing factual about the WW in the text that proves any of these characters right or wrong according to any theory of magic put forth (no coherent theory IS put forth directly), and no explanation of why something is dark magic or not. So no, the text does not state directly what dark magic actually is as a type of magic. That is up to the reader to decide for themselves, to interpret. (The author might *intend* something to be read a certain way, but that does not mean it is actually present in the text in that way. Not all authors meet their every intention perfectly; it's probably impossible.)