EXPLANATION OF LAWS. 337 



§ 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 Avhich connects any two links, not proximate, in a chain of causa- 

 tion, is resolved into the laws which connect each with the intermediate 

 links. Both of these are cases of resolving one law into tAvo 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 gen- 

 eral supposition, consisting of what all those classes of cases have in com- 

 mon. We may here remark that this last operation involves none of the 

 uncertainties attendant on induction by the Method of Agreement, since we 

 need not suppose the result to be extended by way of inference to any new class 

 of cases different from those by the comparison 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 certain, in other words, more universally true 

 than themselves ; they are, in fact, proved not to be themselves laws of na- 

 ture, 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. N"o 

 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 exception 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 un- 

 known, 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 

 mystery for another ; and does nothing to render the general course of na- 

 ture other than mysterious : we can no more assign a lohy for the moi-e 

 extensive laws than for the partial ones. The explanation may substitute 

 a mystery which has become familiar, and has grown to seem not mysteri- 

 ous, for one which is still strange. And this is the meaning of explanation, 

 in common pai'lance. But the process with which we are here concerned 

 often does the very contrary : it resolves 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 tendency 

 of all particles of matter toward one another. It must be kept constantly 

 in view, therefore, that in science, those who speak of explaining any phe- 

 nomenon mean (or should mean) pointing out not some more familiar, but 

 merely some more general, phenomenon, oi which it is a partial exemplifica- 

 tion ; or some laws of causation which produce it by their joint or succes- 

 sive action, and from which, therefore, its conditions may be determined 

 deductively. Every such operation brings us a step nearer toward answer- 

 ing the question which was stated in a previous chapter as comprehending 

 the whole problem of the investigation of natui'e, viz. : what ai-e the fewest 

 assumptions, which being granted, the order of nature as it exists would 

 be the result? What are the fewest general propositions from which all 

 the uniformities existing in nature could be deduced ? 



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