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we possess, aud the errors may nearly all be traced to 

 one of three sources, viz. : (i) I^ove of the marvellous ; 

 (2) Confounding inferences or explanations of facts 

 with the facts themselves ; and (3) Failure to recognise 

 the proportion which must exist between the proba- 

 bility of an occurrence and the kind of evidence which 

 is required to establish it. These defects are not only 

 the cause of the errors to which I have alluded, but lie 

 at the root of most of the superstitions and quackeries 

 in the world ; I will give one or two instances in illus- 

 tration and support of this statement. A good many 

 years ago I picked up a book on animal intelligence 

 by a distinguished scientific author, I will not mention 

 names as I am only mentioning the matter as an 

 illustration, and have not got the book to refer to. In 

 the preface the author deprecated the fact that we 

 depended for our accounts of animal intelligence on 

 unscientific people who were not accustomed to weigh 

 evidence, and led one to anticipate very diff'erent results 

 now that the subject had fallen into competent hands 

 and that all the information would be carefully investi- 

 gated and might be implicitly relied on. Turning over 

 the leaves I found the story of a cat which used to 

 scatter bread crumbs in a garden, and then lie in wait 

 and pounce on the birds which had been attracted by 

 its ingenious artifice. This interesting occurrence had 

 not been actually observed by the author himself, 

 which was a great pity, but he gave it as authenticated 

 by a thoroughly reliable witness. I went on and pre- 

 sently came to an account of a horse which belonged 

 to the author (as well as the story). This animal used 

 to draw the slide of a corn shoot when it wanted a feed 

 of corn and open a window by pulling a cord 07i hot 



