An Introduction to a Biology 



fidence and certainty, and well pleased with himself, 

 and said, " I have now got a theory which fits all 

 the facts," I could think one of two alternative 

 things about him. 



I could think that this man, by a miracle of 

 energy, had become acquainted with all the mani- 

 festations of sex, and that his theory did fit, down 

 to the very smallest undulation, the surface of the 

 phenomenon, as a glove fits a woman's hand. That 

 is to say, I should think that he had made up the 

 deficit in the facts by the discovery of the remainder, 

 and that he was now able to give a theory which fitted 

 exactly, simply because he had now got all the facts 

 at his disposal. 



Or, I could think that he had not made any 

 difference in the stock of facts at his disposal, but had 

 invented a new theory, which fitted the same number 

 of (but probably fewer) facts, only in the sense that 

 a child's hand can be fitted into a steel gauntlet. 

 That is to say, I should think he had made a new 

 theory which really bore very little relation to the 

 facts ; touched them at one or two points but fitted 

 them at none. The theory might be a perfectly 

 consistent one. He would not invent a theory which 

 was not a consistent and organic whole. Indeed it 

 is generally admitted that it is more important that 

 a theory should be consistent with itself than that 

 it should fit the facts closely. For it is considered 

 that the worst thing that can be said against a man 

 who is patiently trying to fit one part of his theory 

 to one set of facts and another part of it to another 

 set, is that the two parts of his theory are not con- 

 sistent with one another. 

 D 33 



