414 THE POPULAR SCIENCE MONTHLY. 



conjure meaning out of facts by pretending to put an explanation 

 upon them, that we will not ascribe the critical mood of the last gen- 

 eration to mere revulsion from the profuse hypotheses of the period 

 when Chemistry promised to reveal the secret constitution of Nature ; 

 but, clearly, after a time of discovery and accumulation of facts, there 

 comes the necessity for arrangement, classification, method, and the 

 logician takes the place of the discoverer. To this work the genera- 

 tion of 1820-1850 set itself in no scholastic spirit, and one of its first 

 achievements in the new field was Herschel's picturesque and elevated 

 " Discourse." ^ Ardent and imaginative as is that fine essay, it is 

 nevertheless essentially logical. Four of his nine " rules of philoso- 

 phizing" were converted by Mill into the experimental methods, and 

 thus made a part of the logic of proof ; his conception of a law is pre- 

 dominantly that of a generalization which seems to imply no inductive 

 leap ; and he appears to look for the openings to future discovery in 

 the purely analytic direction of finding some more general laws of 

 which the laws already discovered are teases. So faithfully did the 

 work embody the tendencies of the period that its phraseology at once 

 became classic, and its ideas of cause and law the commonplaces of 

 science. They certainly formed a large portion of the mental pabu- 

 lum of Mill, and are reflected, though with infinite widening and clari- 

 fication, in the " System of Logic." We have already said that his 

 four "methods" were but four of Herschel's "rules;" Herschel's "pre- 

 sumed permanence of the great laws of Nature " appears in Mill as 

 the statement that " the uniformity of the course of Nature is the ulti- 

 mate major premise in all cases of induction," and the relations of in- 

 duction and deduction, the value and test of hypotheses, the nature of 

 empirical laws, and the analysis of cause — are all striking aper^us 

 which Mill pursued to their limits on every side, and thus was able to 

 give to the exposition of them systematic completeness. All these 

 conceptions, as being important parts of the logic of science, belong 

 equally to the logic of psychology, and, if their statement in reference 

 to mental science is due to Mill, the statement of them in reference to 

 science generally is due to Herschel. But we are here more concerned 

 to point out that the scientific conditions laid down by Mill as defin- 

 ing the logical status of psychology belong to the type of physical 

 investigations of which Herschel was an 'Carly representative. The 

 definition of science as having for its subject " uniformities," the de- 

 scription of the independence of a science as arising out of the irre- 

 ducibility of its laws to other laws, and the exposition of the limits 

 ot scientific inquiry — all find th«r prototypes in the " Discourse." 

 Here again, therefore, the advance in Psychology, though only logi- 

 cal, had its initiative in the physical sciences. 



The rate of change quickens as the type of social structure rises, 

 and the progress made by Psychology within the present generation 

 ^ " Preliminary Discourse on the Study of Natural Philosophy," 1830. 



