The Inner Life, v. I/Fifth Section/XII
SOMNAMBULISM
You ask what is the cause of sleep-walking. I have never had the opportunity of observing a case of somnambulism, so I am unable to speak from direct knowledge; but from reading accounts of such cases I should imagine that the phenomena may be produced by several widely different causes. There are instances in which it appears that the ego is able to act more directly upon his physical body during the absence of the intermediate mental and astral vehicles — instances in which a man during his sleep is able to write poetry or to paint pictures which would be far beyond his powers when awake.
There are other cases in which it is obvious that the dim consciousness inherent in the physical body is working uncontrolled by the man himself, so that it performs quite meaningless acts, or carries out to some extent the idea which was dominant in the mind before falling asleep. To this class belong the stories of servants who have risen in the middle of the night to light the fire, of ostlers who have harnessed horses in their sleep, and so on.
Again, there are cases in which some outside intelligence, whether incarnate or discarnate, has seized upon the body of a sleeping man and used it for his own ends. This would be most likely to happen with a person who is what is called mediumistic — that is to say, whose principles are more loosely joined together than usual, and therefore more readily separable; but oddly enough there seems to be a type of somnambulism which is due to a directly opposite condition, when the principles fit more tightly than usual, so that when the man would naturally visit some neighboring spot in his astral body, he takes the physical body along with him as well, because he is not wholly dissociated from it. Somnambulism is probably also connected with the whole complex problem of the various layers of consciousness in man, which under perfectly normal circumstances are unable to manifest themselves.