IX. 



DEDUCTION. -EXPLANATION OF KNOWN FACTS. 



IMPORTANCE OF THEORY TO GOOD 



OBSERVATION. 



DARWIN fell upon the true cause of the 

 modification of species so early, that the 

 greater number of his special investigations 

 took on a deductive cast. 1 His reflections upon 

 the known facts and principles of biology took 

 the form of efforts to explain them as deduc- 

 tions from his theory; and many of his new 

 discoveries were foreseen as consequences of 

 it. Hence the inductive process does not play 

 so important a part in his work as does the 

 inverse process of deduction. 



It will not be necessary to dwell long upon 

 his success in giving the proper theoretical ex- 

 planations to already known facts and empirical 

 laws. It had required centuries of painstaking 

 research and numberless efforts at classification 

 before anything like a natural classification was 



1 See the Chapter on the Logical History of the Principle 

 of Natural Selection,/^/, p. 212. 



