HALLUCINATIONS OF THE SENSES. 701 



into it. There can be no doubt of the mental disorder of persons who 

 suffer in this way, but it must not be supposed that hallucinations of 

 sight do not occur to persons who are free from mental disorder. I 

 cannot help thinking that they furnish the explanation of the firm be- 

 lief in ghosts and apparitions which has prevailed among all nations 

 and in all times. A belief so universal must have some deep foundation 

 in the facts of Nature or in the constitution of man. One may freely 

 admit that persons have seen apparitions and have heard voices which 

 they thought to be supernatural ; but, inasmuch as seeing is one thing, 

 and the interpretation thereof quite another thing, it may be right to 

 conclude that they were nothing more than hallucinations, and that the 

 reason why no ghosts are seen now, when people pass through church- 

 yards on dark nights, as our forefathers saw them, is that ghosts are 

 not believed in nowadays, while we have gained a knowledge of the 

 nature of hallucinations, and of the frequency of their occurrence, 

 which our forefathers had not. 



One does not fail to notice, when proper attention is given to the 

 subject, a fact which is full of meaning, viz., that the apparitions which 

 have been seen at different ages were in harmony with the dominant 

 ideas or beliefs of the age. It is not probable that any one could be 

 found at the present day to affirm that he had seen an old woman riding 

 through the air on a broomstick to a witches' meeting, because the belief 

 in witchcraft is happily wellnigh extinct ; but two or three hundred 

 years ago, when it would have been thought something like blasphemy 

 to doubt the being and doings of witches, persons of character and 

 veracity might have been found to avouch it solemnly. In like manner, 

 apparitions of Satan were not very uncommon in the middle ages to 

 persons who, like Luther, were in earnest spiritual conflict with him ; 

 but there is no instance on record, so far as I know, of such an appari- 

 tion having ever been seen by an ancient Greek or Roman. The Satan 

 of the middle ages who gave Luther so much trouble had not then been 

 invented. Spirits, ghosts, then, and all apparitions of the same kind, 

 I was prepared to have pronounced unhesitatingly to have been hallu- 

 cinations, which would be found on examination to reflect pretty fairly 

 the prevailing ideas of the time concerning the supernatural ; but it 

 occurred to me that it might be prudent, before doing that, to consult 

 the article on apparitions in the latest edition of the " Encyclopaedia 

 Britannica," lest perchance I should be outrunning current authority ; 

 and I have there discovered, to my no small surprise, that it is still an 

 open question whether invisible inhabitants of the unknown world did 

 not take human or other shapes and become visible to men. The writer 

 of the article plainly inclines to the opinion that they do, and that 

 there is more in the matter than science has yet dreamed of. So also 

 think the spiritualists. 



I now go on to consider the mode of production of hallucinations. 

 At the first blush there might seem to be a great gap between such 



