92 SCIENTIFIC INVESTIGATION 



are most presumptuous. You admit that all these oc- 

 currences took place when you were fast asleep, at a 

 time when you could not possibly have known anything 

 about what was taking place. How do you know that 

 the laws of Nature are not suspended during the night ? 

 It may be that there has been some kind of super- 

 natural interference in this case." In point of fact, he 

 declares that your hypothesis is one of which you cannot 

 at all demonstrate the truth, and that you are by no 

 means sure that the laws of Nature are the same when 

 you are asleep as when you are awake. 



Well, now, you cannot at the moment answer that 

 kind of reasoning. You feel that your worthy friend 

 has you somewhat at a disadvantage. You will feel 

 perfectly convinced in your own mind, however, that 

 you are quite right, and you say to him, "My good 

 friend, I can only be guided by the natural probabilities 

 of the case, and if you will be kind enough to stand 

 aside and permit me to pass, I will go and fetch the 

 police." Well, we will suppose that your journey is 

 successful, and that by good luck you meet with a 

 policeman; that eventually the burglar is found with 

 your property on his person, and the marks correspond 

 to his hand and to his boots. Probably any jury would 

 consider those facts a very good experimental verifica- 

 tion of your hypothesis, touching the cause of the ab- 

 normal phenomena observed in your parlor, and would 

 act accordingly. 



Now, in this supposititious case, I have taken phe- 

 nomena of a very common kind, in order that you 

 might see what are the different steps in an ordinary 

 process of reasoning, if you will only take the trouble to 

 analyse it carefully. All the operations I have described, 

 you will see, are involved in the mind of any man of 



