Thinkst thou, oh man! to attain power to gratify thy lusts, to enrich thy coffers, to build houses, to raise thyself to the pinnacle of human admiration: If these are the hopes and desires, thou has reason to lament thy being born: all such desires are immediately from the Devil. (Francis Barret, The Magus, London, 1801)
The knowledge of black magic is an old as the knowledge of good and evil; and as long as magic has been self-consciously practiced, distinction has been made between the black and white varieties. At first the distinction was simple: white magic was either religious magic, performed with the sanction of the gods, or it was magic that did not hurt anyone else. It included such practices as magic healing, divination, use of love charms and potions, and casting spells for finding buried treasure.
Black magic was that which injured another, and was usually illegal, the punishment varying with the degree of harm intended.
In ancient times, the white magician, who might be a priest practicing on one side, was generally respected and admired. Later however, the practitioners of white magic exclusively were often considered witches or black magicians. During the period of the witch trails, the most benevolent wise woman or herbalist might be accused of witchcraft by customers for whom her magic cures did not work.
Under Christianity, black magic came to be defined in terms of association with the Devil rather than the degree of evil in the magic acts themselves. With the increasing credulity of the Church toward the possibility of successfully working black magic, punishment became more and more savage. During the witch trails, the accused were treated as servants of the Devil, who must be prevented from having any chance to use their powers.
Magicians were considered somewhat less dangerous, since the witch-hunters believed that the effectiveness of magic came from making a pact with the Devil, not from merely working spells. However, it was thought unlikely that one who attained magic powers had got them from any but Satanic sources and could use them for good.
It is easy to believe in black magic as the witch-hunters dd, but often quite difficult to believe in the possibility of white magic. Magic can be white only to the degree that a human being can be good, and examples of pure white magic are therefore hard to find. Many magical practices that traditionally have been considered good, such as finding of buried treasure and the use of love charms, are of mixed value. One must consider not only whether the spell actively injures another but also what effect it has on the magician's character. Will obtaining the treasure make him wiser or stronger? Might the woman he desires to win by magic be happier with someone else?
Although the categories of black and white no longer seem especially useful for describing the practice of magic, the would-be magician should be consider carefully the nature of the forces he/she is evoking, and what effect they will have upon him/her.
Dion Fortune's description of black and white magic might be helpful: "White Magic seeks to reach backwards into an outgrown phase of evolution and release forces which have long since been equilibriated into a static force...In Black Occultism a breaking down of organized form into lower types of force takes place. ( Dion Fortune, The Training amd Work of an Initlate, London, 1955)
Information taken from The Complete Book of Magic & Witchcraft revised edition Kathryn Paulsen