TEE VALUE OF SCIENCE 525 



It is, moreover, unimportant; it suffices to remark that there is a 

 law, and that this law, true or false, does not reduce to a tautology. 



Will it be said that if we do not know on the earth a body which 

 does not fuse at 44° while having all the other properties of phos- 

 phorus, we can not know whether it does not exist on other planets? 

 Doubtless that may be maintained, and it would then be inferred that 

 the law in question, which may serve as a rule of action to us who 

 inhabit the earth, has yet no general value from the point of view 

 of knowledge, and owes its interest only to the chance which has placed 

 us on this globe. This is possible, but, if it were so, the law would be 

 valueless, not because it reduced to a convention, but because it would 

 be false. 



The same is true in what concerns the fall of bodies. It would 

 do me no good to have given the name of free fall to falls which 

 happen in conformity with Galileo's law, if I did not know that else- 

 where, in such circumstances, the fall will be probably free or approxi- 

 mately free. That then is a law which may be true or false, but 

 which does not reduce to a convention. 



Suppose the astronomers discover that the stars do not exactly obey 

 Newton's law. They will have the choice between two attitudes; they 

 may say that gravitation does not vary exactly as the inverse of the 

 square of the distance, or else they may say that gravitation is not 

 the only force which acts on the stars and that there is in addition a 

 different sort of force. 



In the second case, Newton's law will be considered as the definition 

 of gravitation. This will be the nominalist attitude. The choice 

 between the two attitudes is free, and is made from considerations of 

 convenience, though these considerations are most often so strong that 

 there remains practically little of this freedom. 



We can break up this proposition : (1) The stars obey Newton's law, 

 into two others; (2) gravitation obeys Newton's law; (3) gravitation 

 is the only force acting on the stars. In this case proposition (2) 

 is no longer anything but a definition and is beyond the test of experi- 

 ment; but then it will be on proposition (3) that this check can be 

 exercised. This is indeed necessary, since the resulting proposition 

 (1) predicts verifiable facts in the rough. 



It is thanks to these artifices that by an unconscious nominalism 

 the scientists have elevated above the laws what they call principles. 

 When a law has received a sufficient confirmation from experiment, 

 we may adopt two attitudes : either we may leave this law in the fray ; 

 it will then remain subjected to an incessant revision, which without 

 any doubt will end by demonstrating that it is only approximative. 

 Or else we may elevate it into a principle by adopting conventions 

 such that the proposition may be certainly true. For that the pro- 



