OBJECTS.] INTRODUCTORY. 67 



47. Suppositions or Hypotheses ; their 

 Uses and their Value. 



When our means of observation of any natural fact 

 fail to carry us beyond a certain point, it is perfectly 

 legitimate, and often extremely useful, to make a sup- 

 position as to what we should see, if we could carry 

 direct observation a step further. A supposition of 

 this kind is what is called a hypothesis, and the 

 value of any hypothesis depends upon the extent to 

 which reasoning upon the assumption that it is true, 

 enables us to explain or account for the phenomena 

 with which it is concerned. 



Thus, if a person is standing close behind you, and 

 you suddenly feel a blow on your back, you have 

 no direct evidence of the cause of the blow; and 

 if you two were alone, you could not possibly obtain 

 any; but you immediately suppose that this person 

 has struck you. Now that is a hypothesis, and it is 

 a legitimate hypothesis, first, because it explains the 

 fact ; and secondly, because no other explanation is 

 probable ; probable meaning in accordance with the 

 ordinary course of nature. If your companion 

 declared that you fancied you felt a blow, or that 

 some invisible spirit struck you, you would probably 

 decline to accept his explanation of the fact. You 

 would say that both the hypotheses by which he 

 professed to explain the phenomenon were extremely 

 improbable ; or in other words, that in the ordinary 

 course of nature fancies of this kind do not occur, 

 nor spirits strike blows. In fact, his hypotheses would 

 be illegitimate, and yours would be legitimate; and, 

 in all probability, you would act upon your own. 

 In daily life, nine-tenths of our actions are based 



