304 ON SENSATION AND THE UNITY OF 



object is reproduced in the sensorium; exactly as 

 the diaphragm of a telephone reproduces the mode 

 of motion taken up at its receiving end. In other 

 words, the secondary "intentional species" may 

 be, as the Schoolmen thought the primary one 

 was, the last link between matter and mind. 



None the less, however, does it remain true that 

 no .similarity exists, nor indeed is conceivable, 

 between the cause of the sensation and the sensa- 

 tion. Attend as closely to the sensations of 

 muskiness, or any other odour, as we will, no trace 

 of extension, resistance, or motion is discernible in 

 them. They have no attribute in common with 

 those which we ascribe to matter; they are, in the 

 strictest sense of the words, immaterial entities. 



Thus, the most elementary study of sensation 

 justifies Descartes' position, that we know more of 

 mind than we do of body; that the immaterial 

 world is a firmer reality than the material. For 

 the sensation " muskiness " is known immediately. 

 So long as it persists, it is a part of what we call 

 our thinking selves, and its existence lies beyond 

 the possibility of doubt. The knowledge of an 

 objective or material cause of the sensation, on 

 the other hand, is mediate; it is a belief as con- 

 tradistinguished from an intuition; and it is a 

 belief which, in any given instance of sensation, 

 may, by possibility, be devoid of foundation. For 

 odours, like other sensations, may arise from the 

 occurrence of the appropriate molecular changes 



