The Lucretian theory had, for Lucretius, the advantages of being physical, and of dealing a blow at the hated doctrine of a future life.  For the public it had the disadvantages of being incapable of proof, of not explaining the facts, as conceived to exist, and of being highly ridiculous, as Plutarch observed.  Much later philosophers explained all apparitions as impressions of sense, recorded on the brain, and so actively revived that they seemed to have an objective existence.  One or two stock cases (Nicolai’s, and Mrs. A.’s), in which people in a morbid condition, saw hallucinations which they knew to be hallucinations, did, and do, a great deal of duty.  Mr. Sully has them, as Hibbert and Brewster have them, engaged as protagonists.  Collective hallucinations, and the hallucinations of the sane which coincide with the death, or other crisis in the experience of the person who seemed to be seen, were set down to imagination, ‘expectant attention,’ imposture, mistaken identity, and so forth.

Without dwelling on the causes, physical or psychological, which have been said by Frazer of Tiree (1707), Ferrier, Hibbert, Scott, and others, to account for the hallucinations of the sane, for ‘ghosts,’ Mr. Tylor has ably erected his theory of animism, or the belief in spirits.  Thinking savages, he says, ’were deeply impressed by two groups of biological phenomena,’ by the facts of living, dying, sleep, trance, waking and disease.  They asked:  ‘What is the difference between a living body and a dead one?’ They wanted to know the causes of sleep, trance and death.  They were also concerned to explain the appearances of dead or absent human beings in dreams and waking visions.  Now it was plain that ‘life’ could go away, as it does in death, or seems to do in dreamless sleep.  Again, a phantasm of a living man can go away and appear to waking or sleeping people at a distance.  The conclusion was reached by savages that the phantasm which thus appears is identical with the life which ‘goes away’ in sleep or trance.  Sometimes it returns, when the man wakes, or escapes from his trance.  Sometimes it stays away, he dies, his body corrupts, but the phantasm endures, and is occasionally seen in sleeping or waking vision.  The general result of savage thought is that man’s life must be conceived as a personal and rational entity, called his ‘soul,’ while it remains in his body, his ‘wraith,’ when it is beheld at a distance during his life, his ‘ghost,’ when it is observed after his death.  Many circumstances confirmed or illustrated this savage hypothesis Breath remains with the body during life, deserts it at death.  Hence the words spiritus, ‘spirit,’ [Greek], anima, and, when the separable nature of the shadow is noticed, hence come ‘shade,’ ‘umbra,’ [Greek], with analogues in many languages.  The hypothesis was also strengthened, by the great difficulty which savages feel in discriminating between what occurs in dreams, and what occurs to men awake.  Many civilised persons feel the same difficulty with regard to hallucinations beheld by them when in bed, asleep or awake they know not, on the dim border of existence.  Reflection on all these experiences ended in the belief in spirits, in souls of the living, in wraiths of the living, in ghosts of the dead, and, finally, in God.