THE EVOLUTION OF MIND 



cases, moreover, the intervention of conscious 

 attention only impairs the accuracy of adjust- 

 ment. In billiard playing and rifle shooting, the 

 aim is usually impaired if we stop to think about 

 it; and on the piano it is almost impossible to 

 play triple notes with one hand and double notes 

 with the other if we attempt to measure out the 

 time. 



Purely intellectual acts also become to a cer- 

 tain extent automatic with practice, as was in- 

 deed implied in some of the foregoing illustra- 

 tions. Not only the combination of words into 

 a sentence, but the combination of sentences 

 into a proposition, and the combination of pro- 

 positions into a theory, is effected more and 

 more rapidly, until the process hardly attracts 

 the attention. In a complicated exposition like 

 the present, numerous scientific theorems, at 

 first laboriously comprehended one by one, are 

 wrapped up together and thrown into some 

 subordinate clause of a sentence, the total be- 

 ing so obvious as not to withdraw the attention 

 from the main current of thought while writing. 

 In such facts we have a partial explanation of 

 many of the phenomena of what is called un- 

 conscious or " sub-conscious " thinking. And 

 thus, too, are to be explained those sudden 

 flashes of insight, scientific or poetical, which in 

 early times were attributed to inspiration or dic- 

 tation from without. Obviously without a good 

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