As the student progresses, moreover, he will see that even in the case of Clairvoyant Reverie, the third method of inducing the astral en rapport condition, the clairvoyant does not always lose consciousness. In the case of many advanced and exceptionally well-developed clairvoyants, no trance or sleep condition is induced. In such cases the clairvoyant merely "shuts out" the outside world of sights, sounds and thoughts, by an effort of trained will, and then concentrates steadily on the phenomena of the astral plane. For that matter, the skilled and advanced occultist is able to function on the astral plane by simply shifting his consciousness from one plane to another, as the typist shifts from the small letters of the keyboard to the capital letters, by a mere pressure on the shift-key of the typewriter. The only reason that many clairvoyants manifesting along the lines of the third method, known as "clairvoyant reverie," fall into the trance or sleep condition, is that they have not as yet acquired the rare art of controlling their conscious attention at will--this is something that requires great practice. They find it easier to drop into the condition of semi-trance, or semi-sleep, than it is to deliberately shut out the outer world by an act of pure will. Moreover, you will find that in the majority of the recorded cases of the investigators, the clairvoyance was more or less spontaneous on the part of the clairvoyant person, and was not produced by an act of will. As we proceed to consider the various forms and phases of clairvoyant phenomena, in these lessons, you will notice this fact. There are but few recorded cases of voluntary clairvoyance in the books of the investigators--the skilled clairvoyants, and more particularly the advanced occultists, avoid the investigators rather than seek them; they have no desire to be reported as "typical cases" of interesting psychic phenomena--they leave that to the amateurs, and those to whom the phenomena come as a wonderful revelation akin to a miracle. This accounts for the apparent predominance of this form of clairvoyance--the secret is that the net of the investigators has caught only a certain kind of psychic fish, while the others escape attention.