88 



HABIT AND INTELLIGENCE. 



[chap. 



Life works 

 through 

 the chemi- 

 cal forces, 



as an en- 

 gineer 

 through a 

 machine. 



The vital 

 principle, 



defined. 



Origin of 

 life a ques- 



I have expressed my opinion, that it is in the nature of 

 things impossible for the most characteristically vital pro- 

 ducts to be formed by any inorganic chemistry. I believe 

 they are formed by the action of the ordinary chemical 

 forces, modified and as it were guided by that of the vital 

 principle. Life, or the vital principle, works not by op- 

 posing nor by suspending the action of the physical and 

 chemical forces ; on the contrary, it works through them. 

 The relation of life to the lower forces may be compared, 

 remotely but truly, to the relation of the mechanical 

 engineer to the steam-driven machinery that he constructs 

 and keeps at work; he does not set aside the properties 

 of iron and the force of steam, but he avails himself of 

 them, and works through them to the production of effects 

 which the iron and the steam could not have produced 

 of themselves. 



But even if it could be shown that the chemical actions 

 that go on in the organism are no other than what can be 

 imitated in the laboratory, it would still be certain that 

 life is not a mere resultant from any physical and chemical 

 forces, and that consequently there must be a distinct vital 

 principle. By this expression I only mean that unknown 

 and undiscoverable something, which the properties of 

 mere matter will not account for, and which constitutes 

 the differentia of living beings. To deny the existence of 

 a distinct vital principle, in this sense, is not so much 

 untrue as unmeaning. The formation of organic com- 

 pounds is the lowest of organic functions, and is indeed 

 characteristic of vegetables rather than of animals ; above 

 it are the functions of organization, instinct, feeling, and 

 thought, which could not conceivably be resultants from 

 the ordinary properties of matter. 



But we must carefully guard against the error of setting 

 up conceivableness or inconceivableness as a test of truth 

 in questions of fact ; and we must be equally careful not 

 to make any assertion as to matter of fact, in the disguise 

 of the definition of a term. Notwithstanding what I have 

 said in the last paragraph, I freely admit that all questions 

 concerning the origin of life are questions of fact, and 



