Preface 



explanatory formula derived from an exhaustive study 

 of the simpler, and so onwards from the base to the 

 summit. 



The second starts from the principle that for any 

 given order of facts there can be no true explanation 

 which is not capable of application to all the facts of 

 that order. This method seeks first for an explanation 

 capable of covering the most complex phenomena; and 

 this being easily extended a fortiori, to the simpler and 

 lower ones, will necessarily be conformable to all the 

 available data. 



This method thus proceeds from the summit to 

 the base. 



It frequently happens, we must concede, that the 

 second method ends in an impossibility. It will do 

 so whenever the data of fact are insufficient. It must 

 then be admitted to be inapplicable, and should be 

 held in reserve, disregarding minor points in which 

 it may be satisfactory, such details being necessarily 

 inadequate as a basis of reasoning since they refer to 

 only one aspect of the problem. 



Of these two methods, the former being primarily 

 analytic, pertains to pure science. The second, primarily 

 synthetic, pertains to pure philosophy. 



Now when questions arise which pertain both to 

 philosophy and to science, it is necessary to consider 

 which of these two methods should be adopted. 



Once a general truth has been established it matters 

 little whether the explanation of different phenomena 

 leading to a known conclusion starts from the base or 

 the summit; the line of synthesis being known, it is 

 not possible to stray. But when the task before us is 

 to ascertain truth and to establish a synthesis, it becomes 

 necessary to choose and to consider with care which 

 method is likely to prove the more sure and fruitful 

 of results. The first method is the one almost exclusively 

 employed as the foundation for current theories. Its 



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