Although the term "magic" has been defined differently, it is perhaps best defined as the practice of deliberately soliciting or directing the supernatural for purposes of obtaining power over the natural. "Supernatural" refers to a spiritual agent which can, or is believed to be able, to act in this world. Because the supernatural is merely a part of the spiritual, magic can be more broadly defined as the attempt to harness the spiritual for purposes of directing the mundane. All forms of magic have in common the invocation/manipulation of the supernatural/spiritual to direct the natural/material.
This broad definition, of course, can overlap with legitimate religious practices. Consequently, many modern scholars distinguish between magic and religion by discerning the type of spirit invoked: Magic invokes demonic powers; religion invokes the divine. This approach is favored because it supposedly provides a “bright line” distinction.
Unfortunately, this bright line distinction is terribly inadequate. Under this approach, a man can invoke God for purposes of attaining invisibility so he can better spy on naked women, and call it a religious practice. The modern approach places magicians and religious persons on the same moral level, the level of neutrality. In addition, the approach cannot discern whether a practice is magical or religious when the practitioner neither knows nor defines what spirit he solicits, as in astrology's solicitation of undefined cosmic forces.
The modern distinction was formulated in opposition to the traditional Christian approach, which ignored the type of spirit evoked. It concentrated on the difference between supplication (asking the spirit for help–religion) and coercion (forcing the spirit to help–magic).
I favor what might be called an "existential" approach. It looks at the magician or religious person's state of existence (primarily, the state of his soul) as displayed in his actions. Religion submits to the spirit; magic, in its desire for worldly power, seeks to manipulate it. At least one modern scholar would agree with this approach: "Religion, then, at its best perhaps demands of its practitioners a disposition rather different from that required by magic at its mightiest. Religion in this sense requires reverence, an inclination to trust, to be open and to please, and be pleased by, powers superior in every way to humankind; magic may wish to subordinate and to command these powers." (Valerie I.J. Flint, The Rise of Magic in Early Medieval Europe (Princeton University Press, 1991), 8)