I hope that the criticisms which I have been moved to make about the Occultists in preceding passages have been sufficiently stringent to clear me of any suspicion of being unduly credulous or over-ready to accept their statements as authoritative. There are many things in their methods and their teachings which excite my distrust and antipathy. None the less I think it foolish to ignore every statement which happens to be supported by, or to form part of, Occult doctrine. I think it highly probable for instance that clairvoyant descriptions of facts concerning the Etheric Double are often reliable. We have seen that the whole question of its study is probably a matter of observing, directly or indirectly, by ultra-violet light. We also have reason to suppose that the retina of the eye can be rendered abnormally sensitive to light of this frequency by artificial means. But if such abnormal retinal sensibility can be induced artificially, it is very probable that it may sometimes occur naturally. Hence, if the E.D. actually exists, as the evidence undeniably suggests, it is not only possible but probable that certain people will be able to see it without invoking artificial aid. It must be remembered that observations of this kind contain, in themselves, no sort of "supernatural" element, although they may, of course, receive the most strange and erroneous interpretations at the hands of the uninformed. When we turn to Occult literature we find that the theory of the E.D. is worked out in considerable detail. It is said to be violet-grey or blue-grey in colour and to interpenetrate the physical body. The "health aura," _i.e._, the physical aura dealt with by Dr. Kilner, is said to be that part of the E.D. which projects beyond the physical body. It is stated that the physical body and the E.D. are not normally separated during life, although in certain nervous conditions the E.D. may be more or less extruded from the physical body. (Compare this with the diagnostic researches of Kilner.) "Anæsthetics drive out the greater part of the E.D., so that consciousness cannot either affect or be affected by the dense (physical) body. In the abnormally organised persons called mediums, dislocation of the etheric and dense bodies easily occurs, and the E.D., when extruded, largely supplies the physical basis for 'materialisations' (and for Crawford's structure. W.W.S.)." "In sleep, when the consciousness leaves the physical vehicle which it uses during waking life, the dense and etheric bodies remain together.... At what is called death the etheric double is drawn away from its dense counterpart by the escaping consciousness; the magnetic tie existing between them during earth life is snapped asunder...." (Taken from "The Ancient Wisdom.")