Claude Lecouteux. Witches, Werewolves and Fairies: Shape Shifters and Astral Doubles in the Middle Ages. Inner Traditions, 2003.
This book deals in large part with secret night adventures, in which people who are asleep, or in a kind of trance, believe that their double is let free either to venture to the realms of heaven, hell or fairyland, or to roam around the world, perhaps in the shape of an animal. Lecouteux argues that this is a survival of a pre-Christian belief in a quasi-physical double, one of three souls. This belief was later transformed by Christian writers into the idea of a single soul.
Lecouteux is aware that modern tales of alien abduction, near death experiences and astral travel are part of this same tradition. Of course few medieval thinkers really thought that people underwent these adventures in their physical bodies, and were aware that during these spiritual adventures the percipient was either asleep or in a kind of trance.
Reading these stories gives the impression that at least some of those involved were narcoleptic, often reporting sudden overwhelming sleepiness, and extraordinary visions, classic descriptions of narcolepsy’s sudden and extremely intense dreams. Like modern UFO abductees, these trance travellers may come back with stigmata on their bodies signifying wounds received by the double whether in some sort of ‘astral body’ or in the form of an animal. Modern abduction stories are then just another variant on an ancient tradition of secret night adventures. -- Peter Rogerson