This section is from the book "The Sacred Book Of Death", by Lauron William De Laurence. Also available from Amazon: The Sacred Book of Death - Hindu Spiritism Soul Transition and Soul Reincarnation.
It may be remarked, where is the use of this counsel and advice since we do not remember it after we have awakened, or how can we profit by it; but it should be remembered that this advice comes from the spirits of the Astral Plane and although the body or outward man may forget, the spirits do not, and they will continue at the proper time to give these ideas, advice and counsel to you and you will realize it as coming to you some time in the future as an inspiration. It is a well known fact that many persons have had a presentment of their death, and even a clear foreknowledge of it. This counsel and knowledge has been given to them by Astral Spirits and it is thus that some persons are enabled to foresee the time of their death or the death of another with perfect exactness. The reason why the physical body feels fatigued or a person may sometimes feel tired and nervous after waking from sleep, is because the spirit, during its emancipation, reacts upon the body in the same manner that you may attach or fasten a kite or balloon to a post, the post is shaken and affected by the movements of the balloon or kite, so it is that the experiences or activity of the soul reacts to the body, and may leave it in a fatigued and nervous condition, and in this explanation will be found the reason why many people are never profited by sleep.
This emancipation or touring of the soul during sleep proves that every human being leads two lives, that is, his relation to the earth plane, which is exterior, and the Occult relation of the soul to spirit realms or the Astral Plane. Practically speaking, of course this does not in itself constitute two lives, but rather two phases of one and the same life, for no person can lead a double life. Many persons who are acquainted with one another, visit one another in this Spiritual or Occult way while asleep. This act of visiting during sleep of friends, relatives, and acquaintances is extremely frequent, and there is scarcely a person who does not experience some phenomena almost every night, and the intuition or impression of it usually remains with them after they awaken, and is often the origin of certain ideas which afterward occur to them as it were, spontaneously without their being able to account for it. In other words, you may have a certain impression, a certain sympathy, or a decided antipathy for a person, that you yourself, that is the outward man, will not be able to account for, but in reality you have obtained this knowledge or im- pression through spirit intercourse which has been carried on during your sleep.
A person can insure the visit of a spirit to him during his sleep by an exertion of his will, by simply literally deciding to himself upon going to sleep, that he will go and meet such and such a person in spirit life and consult or seek his advice regarding a certain matter or thing. If the person who decides to do this is firm and steadfast of mind, after he has gone to sleep his spirit will pass to the Astral Plane, but unless he is of a firm and steadfast mind, his spirit is often far from following out the plan which has been resolved upon by the outward man, as thoughts and ideas of the outward senses do not always interest the spirit or soul when it becomes clairvoyant. There are many times that the same idea or the discovery of a certain thing, oftentimes suggests itself at a certain time to different persons, although they may be at a great distance from one another, for during sleep spirits or souls communicate with one another and thus spirits or souls who are still in the body upon the earth plane awaken and remember what they have seen, heard and learned from spirit life.
It is thus that several persons may have identical ideas at the same time of the same thing, for in this way one spirit on the Astral Plane may often reveal to souls in the body many things without their being aware of it, as the spirits upon the Astral Plane are able to form an idea of the object of our meditation before we pass to sleep. After the spirit or soul passes to the Astral Plane it is no longer encumbered with the physical body and can radiate wherever it pleases in any direction, and the spirit can then hold communication with other spirits with whom it is in sympathy, and it can also, as written above, communicate with other souls while they are still an inhabitant of the body. There is also different souls dwelling on the earth and on the Astral Plane, between which communication is so keen and clear that it enables two persons or spirits to understand each other without having any need of human speech, and it may be well said that they speak the language of spirits.
 
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