PT. i. Astronomy and Geology compared. 1 



the system of Experimental Philosophy which is 

 coupled with the great name of Bacon as its 

 inventor. Some farther consideration of the nature 

 of these three methods may not be superfluous. 



The first of these, viz. the study of abstract science, 

 is distinguished from the other two by not being 

 dependent upon the evidence of facts. When its 

 principles have been determined, it is only necessary 

 to ascertain that the facts are in accordance with 

 the data required by the conditions of the problem ; 

 the result then follows as a matter of necessity. 

 For example, we are perfectly sure that 2 and 2 

 make 4 ; and although we know nothing of the state 

 of matters or of the conditions which exist in Sirius 

 or the Pleiades, or any other of the constellations, 

 yet we are perfectly certain that 2 and 2 must 

 make 4 there as they make 4 here. We are sure 

 that in no quarter of the universe can 2 and 2 make 

 3, or 5, or 7, or any number but 4 ; and it is not 

 necessary to adduce facts in confirmation of this 

 from any experience of the particular state of things 

 in any of these stars. What is true of this first and 

 simplest in the series of the multiplication table 

 must be true of all the others, though they may not 

 be quite so patent to the eyes ; it is as certain that 



