100 INDUCTION. 



For example, I might infer that there are probably 

 inhabitants in the moon, because there are inhabitants 

 on the earth, in the sea, and in the air : and this is 

 the evidence of analogy. The circumstance of having 

 inhabitants is here assumed not to be an ultimate 

 property, but (as it is reasonable to suppose) a conse- 

 quence of other properties; and depending, therefore, 

 in the case of our earth, upon some of its properties 

 as a portion of the universe, but upon which of those 

 properties we know not. Now, the moon resembles 

 the earth in being a solid, opaque, nearly spherical 

 substance ; containing active volcanoes ; receiving heat 

 and light from the sun, in about the same quantity as 

 our earth ; revolving on its axis ; whose materials gra- 

 vitate, and which obeys all the various laws resulting 

 from that property. And I think no one will deny 

 that if this were all that was known of the moon, the 

 existence of inhabitants in that luminary would derive 

 from these various resemblances to the earth, a greater 

 degree of probability than it would otherwise have: 

 although the amount of the augmentation it would be 

 ridiculous to attempt to estimate. 



If, however, every resemblance proved between B 

 and A, in any point not known to be immaterial with 

 respect to m, forms some additional reason for pre- 

 suming that B has the attribute m ; it is clear, e con- 



bustible ingredient. Experiment having subsequently shown that 

 in both instances he guessed right, the prophecy is considered to 

 have done great honour to his scientific sagacity; but it is to this 

 day uncertain whether the praise was merited; whether the guess 

 was, in truth, what there are so many examples of in the history of 

 science, a far-sighted anticipation of a law afterwards to be dis- 

 covered. The progress of science has not hitherto shown ground 

 for believing that there is any real connexion between combusti- 

 jrility and a high refracting power. 



