266 SENSATION AND THE SENSIFEROUS ORGANS. 



fies 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 per- 

 sists, 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 possi- 

 bility, be devoid of foundation. For odours, like other 

 sensations, may arise from the occurrence of the appro- 

 priate molecular changes in the nerve or in the senso- 

 rium, 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 ob- 

 ject as their cause ; but the belief thus generated is a delu- 

 sion. And, if beliefs are properly termed " testimonies 

 of consciousness," 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 emitting 

 particles which give rise to a mode of motion in the 

 sense organ. The sense organ, again, is only a mediate 

 cause by reason of its producing a molecular change in 



