CHAPTER XL 



PHILOSOPHY OF INDUCTIVE INFERENCE. 



WE have inquired into the nature of perfect induction, 

 whereby we pass backwards from certain observed com- 

 binations of events, to the logical conditions governing 

 such combinations. We have also investigated the grounds 

 of that theory of probability, which must be our guide when 

 we leave certainty behind, and dilute knowledge with 

 ignorance. There is now before us the difficult task of 

 endeavouring to decide how, by the aid of that theory, we 

 can ascend from the facts to the laws of nature ; and may 

 then with more or less success anticipate the future 

 course of events. All our knowledge of natural objects 

 must be ultimately derived from observation, and the 

 difficult question arises How can we ever know anything 

 which we have not directly observed through one of our 

 senses, the apertures of the mind ? The utility of reason- 

 ing is to assure ourselves that, at a determinate time and 

 place, or under specified conditions, a certain phenomenon 

 will be observed. When we can use our senses and per- 

 ceive that the phenomenon does occur, reasoning is super- 

 fluous. If the senses cannot be used, because the event 

 is in the future, or out of reach, how can reasoning take 

 their place ? Apparently, at least, we must infer the un- 

 known from the known, and the mind must itself create 

 an addition to the sum of knowledge. But I hold that it 

 is quite impossible to make any real additions to the con- 

 tents of our knowledge, except through new impression^ 

 upon the senses, or upon some seat of feeling. I shall 



