METHOD OF DISCOVERY. 63 



same experience shows that no other animal but man 

 at present wears shoes with hob-nails in them such 

 as would produce the marks in the gravel. I do not 

 know, even if we could discover any of those " missing 

 links" that are talked about, that they would help 

 us to any other conclusion ! At any rate the law 

 which states our present experience is strong enough 

 for my present purpose. You next reach the con- 

 clusion, that as these kinds of marks have not 

 been left by any other animals than men, or are 

 liable to be formed in any other way than by a man's 

 hand and shoe, the marks in question have been 

 formed by a man in that way. You have, further, a 

 general law, founded on observation and experience, 

 and that, too, is, I am sorry to say, a very universal 

 and unimpeachable one, — that some men are thieves ; 

 and you assume at once from all these premisses — and 

 that is what constitutes your hypothesis — that the 

 man who made the marks outside and on the window- 

 sill, opened the window, got into the room, and 

 stole your tea-pot and spoons. You have now arrived 

 at a Vera Causa ; — you have assumed a Cause which 

 it is plain is competent to produce all the phenomena 

 you have observed. You can explain all these pheno- 

 mena only by the hypothesis of a thief. But that is 

 a hypothetical conclusion, of the justice of which you 

 have no absolute proof at all; it is only rendered 

 highly probable by a series of inductive and deductive 

 reasonings. 



I suppose your first action, assuming that you are 

 a man of ordinary common sense, and that you have 



