INTRODUCTION. 51 



the image of the sensation experienced. We then 

 as it were gather from without us the cause of the 

 sensation, and thus produce within the idea of the 

 object which has occasioned it. By a necessary- 

 law of our intelligence, all the ideas of material 

 objects are in time and space. 



we gather it aright, appears to be to this effect : the mind, or per- 

 cipient faculty, perceives nothing but the modification or alteration 

 which the sensorium undergoes. Consequent on this perception is 

 what M. Cuvier terms the image of the sensation there experienced : 

 finally we travel out of ourselves for the cause of this sensation, 

 and assign it to some material object, an idea of which object is 

 then produced within our minds. Now, for the existence of these 

 images and ideas which M. Cuvier adopts as the media of com- 

 munication between the percipient faculty and the material 

 world there is not an iota of evidence. This doctrine bears too 

 much analogy to the exploded and metaphysical jargon of sensible 

 and intellectual species. The opinion, too, that the mind, the 

 moi, can perceive nothing but the alterations of the sensorium, or as 

 Cuvier has it, the modifications of the central masses of the medul- 

 lary system, is likewise unsupported by adequate proofs. Such 

 alterations are indubitably the immediate objects of perception to 

 the mind, and through their medium, however inexplicable it may 

 be, the mind discerns external objects, and is irresistibly impelled 

 by a primary law of its nature to believe in their external exist- 

 ence. 



We may further observe that the language employed in the above 

 passage is very loose. What is meant by the image of a sensation? 

 and by the image being produced by an acquired perception ? 



The conditions of perception are a percipient faculty, a senso- 

 rium, a nervous uninterrupted chain of communication, and external 

 organs ; all these conditions are essential to the perception of 

 material objects. An impression is first made on the external 

 organs of sense, and is communicated by the nervous chain acting 

 as a conductor to the sensorium, when a twofold perception is 

 acquired by the mind ; the first is that of a certain modification 

 which the sensorium has undergone, through the agency of the 

 nervous conductor, which modification conjoined with percep- 



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