PRINCIPLES OF SCIENCE, 5 



own facts, and their own principles. The con- 

 duct of those who take false analogies for the 

 explanation of the same phenomena, or the 

 principles of dissimilar sciences, to account for 

 the effects produced in those to which they 

 have no relation, cannot be too strongly repro- 

 bated and condemned. 



If the mere capacity appertaining to different 

 species of common matter, or even the chemi- 

 cal power which it may be supposed to pos- 

 sess, were employed, as it too often is, to ac- 

 count for the cause of vitality ; if the principles 

 of hydraulics were employed to account for the 

 motion of the fluids in the animated system ; 

 or those of pneumatics for the process of respi- 

 ration ; in short, if the principles of chemical 

 science were advanced to prove the nature of 

 vital action in general, and of ratiocination in 

 particular ; facts, or principles, such as these, 

 would unquestionably be false. The same 

 conclusions may be drawn if the principle of 

 vitality in plants were adduced to prove the 

 principle of instinct in brutes ; or the principle 

 of instinct in brutes employed to ascertain the 

 nature of intellect in man. These facts having 

 no reference whatever to the particular subject 

 which they were intended to demonstrate, and 

 being, in themselves, inefficient and defective to 

 prove the conclusion, must ever be considered 

 as false. The principle of intellect in man can- 



