X.] SENSATION AND THE SENSIFEROUS ORGANS. 259 



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 sensa- 

 tion " 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 contradistinguished 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 in 

 the nerve or in the sensorium, by the operation of a 

 cause distinct from the affection of the sense organ by 

 an odorous body. Such "subjective" sensations are 

 as real existences as any others, and as distinctly 

 suggest an external odorous object as their cause ; but 

 the belief thus generated is a delusion. And, if 

 beliefs are properly termed " testimonies of conscious- 

 ness," then undoubtedly the testimony of consciousness 

 may be, and often is, untrustworthy. 



Another very important consideration arises out of 

 the facts as they are now known. That which, in the 

 absence of a knowledge of the physiology of sensation, 

 we call the cause of the smell, and term the odorous 

 object, is only such, mediately, by reason of its emit- 

 ting particles which give rise to a mode of motion in 



