p<^ 



INDUCTION. 



ally to the lot of a different set of 

 persons from those who studied ter- 

 restrial phenomena, and had, indeed, 

 been a matter of great interest at a 

 time when the idea of explaining 

 celestial facts by terrestrial laws was 

 looked upon as the confounding of an 

 indefeasible distinction. When, how- 

 ever, the celestial motions were ac- 

 curately ascertained, and the deduc- 

 tive processes performed, from which 

 it appeared that their laws and those 

 of terrestrial gravity corresponded, 

 those celestial observations became a 

 Bet of instances which exactly elimin- 

 ated the circumstance of proximity to 

 the earth, and proved that in the 

 original case, that of terrestrial ob- 

 jects, it was not the earth, as such, 

 that caused the motion or the pres- 

 sure, but the circumstance common 

 to that case with the celestial in- 

 stances, namely, the presence of some 

 great body within certain limits of 

 distance. 



§ 6. There are, then, three modes 

 of explaining laws of causation, or, 

 which is the same thing, resolving 

 them into other laws. First, when 

 the law of an effect of combined 

 causes is resolved into the separate 

 laws of the causes, together with the 

 fact of their combination. Secondly, 

 when the law which connects any two 

 links, not proximate, in a chain of 

 causation, is resolved into the laws 

 which connect each with the inter- 

 mediate links. Both of these are 

 cases of resolving one law into two 

 or more ; in the third, two or more 

 are resolved into one : when, after 

 the law has been shown to hold good 

 in several different classes of cases, 

 we decide that what is true in each 

 of these classes of cases is true under 

 some more general supposition, con- 

 sisting of what all those classes of 

 cases have in common. We may 

 here remark that this last operation 

 involves none of the uncertainties at- 

 tendant on induction by the Method 

 of Agreement, since we need not sup- 

 pose the result to be extended by way 



of inference to any new class of cases 

 different from those by the compari- 

 son of which it was engendered. 



In all these three processes, laws 

 are, as we have seen, resolved into 

 laws more general than themselves ; 

 laws extending to all the cases which 

 the former extended to, and others 

 besides. In the first two modes they 

 are also resolved into laws more cer- 

 tain, in other words, more universally 

 true than themselves ; they are, in 

 fact, proved not to be themselves 

 laws of nature, the character of which 

 is to be universally true, but results 

 of laws of nature, which may be only 

 true conditionally, and for the most 

 part. No difference of this sort exists 

 in the third case, since here the 

 partial laws are, in fact, the very 

 same law as the general one, and any 

 exception to them would be an excep- 

 tion to it too. 



By all the three processes, the 

 range of deductive science is extended; 

 since the laws, thus resolved, may be 

 thenceforth deduced demonstratively 

 from the laws into which they are 

 resolved. As already remarked, the 

 same deductive process which proves 

 a law or fact of causation if unknown, 

 serves to explain it when known. 



The word explanation is here used 

 in its philosophical sense. What is 

 called explaining one law of nature by 

 another, is but substituting one mys- 

 tery for another, and does nothing 

 to render the general coiirse of nature 

 other than mysterious : we can no 

 more assign a why for the most exten- 

 sive laws than for the partial ones. 

 The explanation may substitute a 

 mystery which has become familiar, 

 and has grown to seem not mysterious, 

 for one which is still strange. And 

 this is the meaning of explanation, in 

 common parlance. But the process 

 with which we are here concerned 

 often does the very contrary : it re- 

 solves a phenomenon with which we 

 are familiar into one of which we 

 previously knew little or nothing ; as 

 when the common fact of the fall of 

 heavy bodies was resolved into the 



