DEEAMS AND ILLUSIONS. 263 



is not yet fully understood, we must consider the 

 image, so far as it is believed to be real. 



In cases of normal hallucination the reason is 

 intact, and the observer is conscious of the illusion, 

 yet notwithstanding this positive judgment the image 

 has an appearance of complete reality. The cause 

 of this illusion is evidently the same as that of the 

 illusions of dreams, and of the origin of myth ; namely, 

 that everywhere and always the mental or natural 

 phenomenon and its image are respectively entined. 

 In the normal waking state, habit and other causes 

 on which we have touched render our ideas of things 

 altogether immaterial, as merely psychical forms and 

 representative signs, but when the excitement of the 

 organs increases, so as to present them to the con- 

 sciousness as objective images, then, owing to the 

 interruption of the ordinary process, they are sud- 

 denly entined, and appear as an external phenomenon. 

 Hallucinations are therefore explained by our theory, 

 and it is further confirmed by the hallucinations of 

 animals, and especially by the delirium of dogs and 

 other animals affected by hydrophobia, or by cerebral 

 excitement artificially produced by alcoholic and 

 exhilarating drugs. 



If a man is habitually subject to many and 

 various hallucinations, and his sane judgment esteems 

 them to be such, they are undoubtedly unusual 

 phenomena, but they do not in any way injure the 

 rational exercise of the mind. It is only when he 



