THE EXPLANATION OF LAWS 107 



from these in one all-important feature ; it is the fairy 

 tale which appeals to every one, and the fairy tale which 

 nature has agreed to accept. It is not you and I and the 

 man round the corner who find that the conception of 

 iron makes the world intelligible, while the people in the 

 next street do not ; in this matter every single living being 

 in the world (so far as we can ascertain his opinion) 

 agrees with us ; they all accept our fairy tale and agree 

 that it makes the world intelligible. And nature accepts 

 it too ; the law that there is iron enables us to predict, 

 and nature always agrees with our predictions. There 

 is no other fairy tale like this ; there is none that denies 

 that there is iron, a substance with invariably associated 

 properties, which is acceptable to every one and which 

 predicts truly. It is just because our fairy tale is capable of 

 the universal agreement which we discussed in Chapter II 

 that we distinguish it from all other fairy tales and 

 call it solid fact. Nevertheless the fact remains that its 

 value for us is that of other fairy tales, namely that it 

 makes the world intelligible. 



And now let us turn again to theories. Here, it is true, 

 we cannot apply directly the criterion of universal assent. 

 There is actually much more difference of opinion concern- 

 ing the value of theories than there is concerning the value 

 of laws ; and it is impossible to force an agreement as it 

 can be forced in the case of laws. And while that 

 difference of opinion persists we must freely admit that 

 the theory has no more claim on our attention than any 

 other ; it is a fairy tale which may be true, but which is 

 not known to be true. But in process of time the 

 difference of opinion is always resolved ; it vanishes 

 ultimately because one of the alternative theories is 

 found to predict true laws and the others are not. It is 

 for this reason that prediction by theories is so 

 fundamentally important ; it enables us to distinguish 

 between theories and to separate from among our fairy 



