IB PRINCIPLES OF SCIENCE. 



philosophy which continues to prevail at 

 day. I have, perhaps, dwelt longer on this 

 subject than was necessary ; I was, however, 

 led to it in consequence of the complete igno- 

 rance which it appeared to be involved in, by 

 those who ought, from their situation, to have 

 been better instructed and informed ; the idea 

 of false facts was not only decried by them, 

 but even attempted to be ridiculed. 



Having endeavoured to show what true prin- 

 ciples are, and what false principles are not ; 

 I shall now proceed to point out the errors of 

 taking false analogies as principles of science,. 

 Wherever a uniformity of nature and of cha- 

 racter exists between different bodies, analogy 

 becomes a legitimate source of induction; it is 

 from the analogy which subsists between the 

 phenomena of life and health, of disease and 

 death in plants, that these may often be em- 

 ployed to illustrate the correspondent changes 

 which take place in brutes, as well as in the 

 human species. Analogy becomes also a legi- 

 timate source of induction, when a similarity of 

 nature exists between bodies whose functions 

 are the same, however dissimilar they may be 

 in structure and appearance. By analogy we 

 predicate the same attributes to thegills of fish, 

 as we do to the lungs of the mammalia ; to the 

 ovaries of a sprat or of a whale, as to the ova- 

 ries of a rabbit, or of an elephant. And, it is 



