132 LETTERS ON NATURAL MAGIC. 



In darkness and solitude, when external objects no 

 longer interfere with the pictures of the mind, they be- 

 come more vivid and distinct ; and in the state between 

 waking and sleeping, the intensity of the impressions 

 approaches to that of visible objects. With persons of 

 studious habits, who are much occupied with the operations 

 of their own minds, the mental pictures are much more 

 distinct than in ordinary persons ; and in the midst of 

 abstract thought, external objects even cease to make any 

 impression on the retina. A philosopher absorbed in his 

 contemplations experiences a temporary privation of the 

 use of his senses. His children or his servants will enter 

 the room directly before his eyes without being seen. 

 They will speak to him without being heard ; and they 

 will even try to rouse him from his reverie without being 

 felt ; although his eyes, his ears, and his nerves, actually 

 receive the impressions of light, sound, and touch. In 

 such cases, however, the philosopher is voluntarily pursu- 

 ing a train of thought on which his mind is deeply in- 

 terested; but even ordinary men, not much addicted to 

 speculations of any kind, often perceive in their mind's 

 eye the pictures of deceased or absent friends, or even 

 ludicrous creations of fancy, which have no connection 

 whatever with the train of their thoughts. Like spectral 

 apparitions, they are entirely involuntary, and though 

 they may have sprung from a regular series of associa- 

 tions, yet it is frequently impossible to discover a single 

 link in the chain. 



If it be true, then, that the pictures of the mind and 

 spectral illusions are equally impressions upon the retina, 

 the latter will differ in no respect from the former, but in 

 the degree of vividness with which they are seen ; and 

 those frightful apparitions become nothing more than our 

 ordinary ideas, rendered more brilliant by some accidental 

 and temporary derangement of the vital functions. Their 



