The All as One theory states that all forms of magic are evil, irrespective of color (white or black). This view is generally associated with Satanism. People that maintain this opinion include those belonging to most branches of Christianity.
The Dark Doctrine theory states that black magic is the powers of darkness, usually seen from a Left-Hand Path point of view. This may or may not contrast with white magic, depending on the user's acceptance of dualism.
The Formal Differences theory states that the forms and components of black magic are not the same due to the different aims or interests of those casting harmful spells than those of white. Harmful spell-casting tends to include symbolism that seems hazardous or harmful to human beings, such as sharp, pointed, prickly, caustic, and hot element(s) combined with very personal objects from the spell's target (their hair, blood, mementos, etc.). This distinction can primarily be observed in folk magic, but pertains to other types of magic also.
The No Connection theory states that both black and white magic are completely different from the base up and are accomplished uniquely, even if they achieve similar effects. This stance is often presented in fiction, and as a result, the two classes of magic-users are portrayed as being both ideologically and diametrically opposed. In The Lord of the Rings, the Elves find it strange that Humans and Hobbits can even use a single word, "magic", which refers to both forms, as the Elvish tongues regard them also linguistically as completely separate and unrelated.
The Separate but Equal theory states that black and white magic are exactly the same thing, differentiated only by their end goals and intent. According to this theory, the same spell could be either white or black (see gray magic); its nature is determined by the end result of the spell. The majority of religions follow this belief, as does the remainder of fiction that does not follow the No Connection theory. By this interpretation, even such spells commonly seen as good can be misused, so healing could be used to regenerate the body to the point of cancer, for instance.
Origin: esoteric-soup.blogspot.com
