Adherents to magic believe that it may work by one or more of the following basic principles: •
A mystical force or energy that is natural, but cannot be detected by science at present, and which may not be detectable at all. Common terms referring to such magical energy include mana, numen, chi or kundalini. These are sometimes regarded as fluctuations of an underlying primary substance (akasha, aether) that is present in all things and interconnects and binds all. Magical energy is thus also present in all things, though it can be especially concentrated in magical objects. Magical energies are typically seen as being especially responsive to the use of symbols, so that a person, event or object can be affected by manipulating an object that symbolically represents them or it (as in sigil magic, for instance). This corresponds to James Frazer's theory of sympathetic magic.
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Intervention of spirits, similar to hypothetical natural forces, but with their own consciousness and intelligence. Believers in spirits will often describe a whole cosmos of beings of many different kinds, sometimes organized into a hierarchy.
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Manipulation of the Elements, by using the will of the magician and symbols or objects which are representative of the element(s). Western practitioners typically use the Classical elements of Earth, Air, Water, and Fire.
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Concentration or meditation. A certain amount of focusing or restricting the mind to some imagined object (or will), according to Aleister Crowley, produces mystical attainment or "an occurrence in the brain characterized essentially by the uniting of subject and object" (Book Four, Part 1: Mysticism). Magic, as defined previously, seeks to aid concentration by constantly recalling the attention to the chosen object (or Will), thereby producing said attainment. For example, if one wishes to concentrate on a god, one might memorize a system of correspondences (perhaps chosen arbitrarily, as this would not affect its usefulness for mystical purposes) and then make every object that one sees "correspond" to said god.
Aleister Crowley wrote that ". . . the exaltation of the mind by means of magickal practices leads (as one may say, in spite of itself) to the same results as occur in straightforward Yoga." Crowley's magick thus becomes a form of mental, mystical, or spiritual discipline, designed to train the mind to achieve greater concentration. Crowley also made claims for the paranormal effects of magick, suggesting a connection with the first principle in this list. However, he defined any attempt to use this power for a purpose other than aiding mental or mystical attainment as "black magick".
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The magical power of the subconscious mind. To believers who think that they need to convince their subconscious mind to make the changes that they desire, all spirits and energies are projections and symbols that make sense to the subconscious. A variant of this belief is that the subconscious is capable of contacting spirits, who in turn can work magic.
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The Oneness of All. Based on the fundamental concepts of monism and Non-duality, this philosophy holds that Magic is little more than the application of one's own inherent unity with the universe. Hinging upon the personal realization, or "illumination", that the self is limitless, one may live in unison with nature, seeking and preserving balance in all things.
Many more hypotheses exist. Practitioners will often mix these concepts, and sometimes even invent some themselves. In the contemporary current of chaos magic in particular, it is not unusual to believe that any concept of magic works.
Key principles of utilizing Magic are often said to be Concentration and Visualization. Many of those who purportedly cast spells attain a mental state called the "Trance State" to enable the spell. The Trance State is often described as an emptying of the mind, akin to meditation.
http://en.wikipedia.org/wiki/Magic_%28paranormal%29#Hypotheses_of_adherents