In parapsychology and many forms of spiritual practice, an aura is a field of subtle, luminous radiation supposedly surrounding a person or object (like the halo or aureola of religious art) that some people are claimed to be capable of observing by means of their third eye.  The depiction of such an aura in religious art usually connotes a person of particular power or holiness.
According to the literature of Theosophy, Anthroposophy, and Archeosophy, each color of the aura has a precise meaning, indicating a precise emotional state. A complete description of the Aura and its colors was provided by Charles Leadbeater, a theosophist of the 19th century. The works of Leadbeater were later developed by Palamidessi and others.
Skeptics such as Robert Todd Carroll contend that auras may be seen for explainable reasons such as migraines or synesthesia. Some people see auras as the result of a migraine, epilepsy, a visual system disorder, or a brain disorder. Eye fatigue can also produce an aura, sometimes referred to as eye burn.
W.E. Butler has connected auras with clairvoyance and etheric, mental, and emotional emanations. He classifies aura into two main types: etheric and spiritual. Robert Bruce classifies auras into three types: etheric, main, and spiritual. Various books have been written that derive various personality traits based upon the specific colors of the different layers of the aura. Auras are thought to be related to the etheric subtle body and to serve as a visual measure of the state of the health of the physical body. Auras are not thought to be actual light but a translation of other unknown sensory readings that is added to our visual processing. According to Bruce they are not seen in complete darkness and cannot be seen unless some portion of the person or object emitting the aura can also be seen.
In martial arts
Glenn Morris, grandmaster head of the Hoshin Roshi Ryu lineage, included perception of the aura in his training of advanced martial artists. His experience was that it consisted of multiple layers. He described the most easily visible of these as being "light and denser than the air in which the body is immersed", typically half to quarter of an inch thick and correlating with the etheric body of an individual. Around this he described a yard thick egg-shaped layer reflecting hormonal state that he linked to the emotional body, and outside this, other barely perceptible layers corresponding to the mental body and beyond.
Recalling the aura of another sōke, he wrote: "The first time I saw Hatsumi, he was running continuous bright, lime, neon green a foot wide and was so easy to see he would flash in bright sunlight".
Recognition of auras has occasionally been scientifically tested. One test involved an aura reader standing on one side of a room with an opaque partition separating her from a number of slots which might contain either actual people or mannequins. The aura reader failed to identify the slots containing people, incorrectly stating that all contained people. In another test, which was televised, another aura reader was placed before a partition where five people were standing. He claimed that he could see their auras from behind the partition. As each person moved out, the reader was asked to identify where that person was standing behind the slot. He identified only 2 out of 5 correctly.
- Jack, Alex The New Age Dictionary First Edition: Kanthaka Press:1976; Second Edition Japan Publications, Inc. Tokyo and New York:1990 (Page locations taken from Second Edition)--See definition of "Aura" page 14; Definition of "Third Eye" Page 200
- http://parapsych.org/glossary_a_d.html Parapsychological Association website, Glossary of Key Words Frequently Used in Parapsychology, Retrieved January 24, 2006
- LeadBeater, Charles: Man: Visible and Invisible, 1902.
- Palamidessi, Tommaso: The Occult Constitution of Man and Woman, 1968.
- http://www.skepdic.com/auras.html The Skeptic's Dictionary by Robert Todd Carroll, entry on auras, Retrieved Oct 13, 2007
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- Butler, W.E.: How to Read the Aura, pp 181-182. Destiny Books, 1978.
- Bruce, Robert: Auric Mechanics and Theory, "Capturing the Aura," pp 301-303. Blue Dolphin Publishing, 2000.
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- Swami Panchadasi, The Human Aura. Astral Colors and Thought Forms, Advanced Thought Publishing, Chicago, 1916. (PDF