VI POSSIBILITIES AND IMPOSSIBILITIES 205 



expectations, based upon careful observations of 

 past events, are, as a rule, trustworthy. We 

 should be foolish indeed not to follow the only guide 

 we have through life. But, for all that, our highest 

 and surest generalisations remain on the level of 

 justifiable expectations ; that is, very high proba- 

 bilities. For my part, I am unable to conceive of an 

 intelligence shaped on the model of that of man, 

 however superior it might be, which could be any 

 better off than our own in this respect ; that is, 

 which could possess logically justifiable grounds 

 for certainty about the constancy of the order of 

 things, and therefore be in a position to declare 

 that such and such events are impossible. Some 

 of the old mythologies recognised this clearly 

 enough. Beyond and above Zeus and Odin, there 

 lay the unknown and inscrutable Fate which, one 

 day or other, would ^crumple up them and the 

 world they ruled to give place to a new order of 

 things. 



I sincerely hope that I shall not be accused of 

 Pyrrhonism, or of any desire to weaken the foun- 

 dations of rational certainty. I have merely 

 desired to point out that rational certainty is one 

 thing, and talk about " impossibilities," or " viola- 

 tion of natural laws," another. Rational certainty 

 rests upon two grounds the one that the evidence 

 in favour of a given statement is as good -as it can 

 be ; the other that such evidence is plainly insuffi- 

 cient. In the foimer case, the statement is to be 



