X. 



DEDUCTION. ANTICIPATION. 



A VERY few negative instances have been 

 ** given to show the importance of theory 

 for accurate observation. They illustrate how 

 the absence of theory led to the oversight or 

 neglect of facts which later, under the sway 

 of theory, have become important. Darwin's 

 works are full of instances in which he was led 

 by his theory to anticipate the facts of nature. 

 It was inevitable that, having so early dis- 

 covered the theories which covered the whole 

 territory in which he worked, he should be 

 guided by them in the search for facts, and 

 that his work should thenceforth be deductive 

 in its character. Examples of this character- 

 istic method range from the great deductions 

 which led to nearly all his important special 

 investigations, and which illustrate the sweep- 

 ing consequences of his general theories, to the 

 little deductive details which show how swift 

 and accurate his prevision became even in the 

 matter of minute consequences of these theories. 



