Some explanation as to the nature of the vrittis is perhaps necessary here. The vrittis are those activities of the mind which eventuate in the conscious relation between the sense employed and that which is sensed. Apart from a certain modification of the mental process or an assertion of the I-am-I realization, the senses might be active yet the man be unaware of them. The man is aware that he sees, tastes or hears; he says, "I see, I taste, I hear," and it is the activity of the vrittis (or those mental perceptions which have relation to the five senses) which enables him to recognize the fact. By withdrawing himself from active sense perception, by no longer [22]  utilizing the "outward-going" consciousness, and by abstracting that consciousness from the periphery to the center, he can bring on a condition of passivity, - a lack of awareness, which is not the samadhi of the yogi, nor the achievement of one-pointedness such as the student of yoga aspires to, but which is a form of trance. This self-imposed quieting is not only a detriment to the achievement of the highest yoga but is excessively dangerous in many cases.

1. The ordinary sleep of the physical body, where the brain does not respond to any sense contacts;
2. Sleep of the vrittis, or of those modifications of the mental processes which correlate the man with his environment, through the medium of the senses and the mind; [23]
3. The sleep of the soul, which, occultly speaking, covers that part of human experience which dates from a man's first human incarnation until he "awakens" to a knowledge of the plan, and endeavors to bring the lower man into line with the nature and will of the inner spiritual man;
4. The sleep of the ordinary medium, wherein the etheric body is partially extruded from the physical body, and is likewise separated from the astral body, bringing in a condition of very real danger;
5. Samadhi, or the sleep of the yogi, the result of the conscious scientific withdrawal of the real man from his lower threefold sheath in order to work on high levels, preparatory to some active service upon the lower;
6. The sleep of the Nirmankayas, which is a condition of such intense spiritual concentration and focusing in the spiritual or atmic body that the outward going consciousness is withdrawn not only from the three planes of human endeavor but likewise from the two lower expressions of the spiritual Triad. For purposes of his peculiar and specific work the Nirmankaya "sleeps" to all states save that of the third, or atmic plane.