550 INDUCTION. 



further observation detects an intermediate link ; a 

 fact caused by the antecedent, and in its turn causing 

 the consequent; so that the cause at first assigned is 

 but the remote cause, operating through the inter- 

 mediate phenomenon. A seemed the cause of C, but 

 it subsequently appeared that A was only the cause 

 of B, and that it is B which was the cause of C. For 

 example : mankind were aware that the act of touch- 

 ing an outward object caused a sensation. It was, 

 however, at last discovered, that after we have touched 

 the object, and before we experience the sensation, 

 some change takes place in a kind of thread called a 

 nerve, which extends from our outward organs to the 

 brain. Touching the object, therefore, is only the 

 remote cause of our sensation ; that is, not the cause, 

 properly speaking, but the cause of the cause ; the 

 real cause of the sensation is the change in the state 

 of the nerve. Future experience may not only give 

 us more knowledge than we now have of the particular 

 nature of this change, but may also interpolate another 

 link : between the contact (for example) of the object 

 with our outward organs, and the production of the 

 change of state in the nerve, there may take place some 

 electric phenomenon. Hitherto, however, no such 

 intermediate agency has been discovered ; and the 

 touch of the object must be considered, provisionally 

 at least, as the proximate cause of the affection of 

 the nerve. The sequence, therefore, of a sensation of 

 touch upon contact with an object, is ascertained not 

 to be an ultimate law ; is resolved, as the phrase is, 

 into two other laws, the law, that contact with an 

 object produces an affection of the nerve ; and the 

 law, that an affection of the nerve produces sensa- 

 tion. 



To take another example : the more powerful acids 



