228 THE METHOD OF DARWIN. 



could never have been detected by their direct 

 study." Writing of the celestial motions as 

 an illustration, he continued, "How could we 

 ever have ascertained the combination of forces 

 on which the motions of the earth and planets 

 are dependent by merely comparing the orbits 

 or velocities of different planets or the different 

 velocities and positions of the same planet ? " 



Darwin himself did not discover the cause by 

 the direct study of the effects ; but his efforts 

 to reach a cause inductively gave him such an 

 insight into variations and adaptations that he 

 could prosecute vigorously the other two steps, 

 deduction and verification, when once the cause 

 was given. What Mill said of celestial motions 

 could be almost literally quoted of adaptations. 

 It would hardly be going beyond the facts to 

 say that the history of theories proves that 

 usually not even preliminary hypotheses con- 

 cerning causes are worked out directly from an 

 analysis of effects; but the causes are usually 

 caught in action during the effort to discover 

 them inductively, or are reached in a round- 

 about way. 



