PESSIMISM AND POSITIVE SCIENCE. 221 



act accordingly. This is the case too with the practical 

 inventor, with the physician who deals with our bodily 

 disorders, as well as with the political reformer who 

 attempts to cure the social maladies. The physician 

 requires only to know the laws of the human body, 

 the causes of diseases and their remedies, without 

 raising the question of what is " vitality " in itself, or 

 what is the ultimate cause of life ; the inventor of the 

 steam-engine required only, in addition to his own 

 inventive genius, a knowledge of the laws of heat, of 

 motion, of the propulsive power of steam, without once 

 being required to raise the inquiry whether heat, and 

 steam, and motion were anything in themselves other 

 than their phenomenal appearances, or whether a hidden 

 reality or entity lay under or behind them, what was the 

 real nature of heat, or how it could possibly transmute 

 itself into motion, questions which, however absorbing 

 and interesting to the metaphysician, would be entirely 

 irrelevant from the point of view of the inventor 

 who conceived, or of the engineer who constructed, the 

 machine. In all cases, however the metaphysical ques- 

 tions be answered, or whether they be answered at all, 

 concerns not the man of practice. In all the practical 

 arts, in all the sciences that relate to practice, for the 

 prudent conduct of life, for the moral conduct of life, as 

 weU as for all purposes of scientific, that is, of real and 

 possible, explanation of Nature, man requires nothing 

 more than the knowledge of phenomena and their in- 

 variable successions and coexistences ; while for the 

 effectual discovery of these laws of phenomena amidst 

 the complexity and obscurity of their involved circum- 

 stances, he requires only that positive inductive method 

 of interrogating Nature first conceived and pointed out 

 by Bacon, which has since been so successfully applied in 



