THE SCIENTIFIC LAW 99 



description — it is simply a briefer, more accurate, and 

 more wide-embracing statement. The one can just as 

 fitly as the other be termed a natural law. 



The law of gravitation is a brief description of Jiow 

 every particle of matter in the universe is altering its 

 motion with reference to every other particle. It does 

 not tell us why particles thus move ; it does not tell us 

 why the earth describes a certain curve round the sun. 

 It simply resumes, in a few brief words, the relationships 

 observed between a vast range of phenomena. It econo- 

 mises thought by stating in conceptual shorthand that 

 routine of our perceptions which forms for us the universe 

 of gravitating matter. 



We have in the law of gravitation an excellent 

 example of a scientific law. We see in its evolution 

 the continual struggles of the human mind to reach a 

 more and more comprehensive and exact formula, and 

 at last Newton reaches one so simple and so wide- 

 embracing that many have thought nothing further can 

 be achieved in this direction. " Here," says Paul du 

 Bois-Reymond, " is the limit to our possible knowledge." 

 If the reader once grasps the characteristics of this law 

 of Newton's he will understand the nature of all scientific 

 law. Men study a range of facts — in the case of nature 

 the material contents of their perceptive faculty — they 

 classify and analyse, they discover relationships and 

 sequences, and then they describe in the simplest possible 

 terms the widest possible range of phenomena. How 

 idle is it, then, to speak of the law of gravitation, or 

 indeed of any scientific law, as ruling nature. Such laws 

 simply describe, they never explain the routine of our 

 perceptions, the sense -impressions we project into an 

 "outside world." 



The scientific law, while thus the product of a rational 

 analysis of facts, is always liable to be replaced by a 

 wider generalisation. Such replacement of one formula 

 by another is indeed the regular course of scientific pro- 

 gress. The only final test we have of the truth of any 

 law, of the sufficiency of its description, the only proof 



