SCIENCE.] INTRODUCTORY. 13 



unsupported ; it is a law of nature that, under or- 

 dinary conditions, lead is soft and heavy, while flint 

 is hard and brittle ; because experience shows us that 

 heavy things always do fall if they are unsupported, 

 that, under ordinary conditions, lead is always soft 

 and that flint is always hard. 



In fact, everything that we know about the powers 

 and properties of natural objects and about the order 

 of nature may properly be termed a law of nature. 

 But it is desirable to remember that which is very 

 often forgotten, that the laws of nature are not the 

 causes of the order of nature, but only our way of 

 stating as much as we have made out of that order. 

 Stones do not fall to the ground in consequence of 

 the law just stated, as people sometimes carelessly 

 say ; but the law is a way of asserting that which in- 

 variably happens when heavy bodies at the surface of 

 the earth, stones among the rest, are free to move. 



The laws of nature are, in fact, in this respect, similar 

 to the laws which men make for the guidance of their 

 conduct towards one another. There are laws about 

 the payment of taxes, and there are laws against 

 stealing or murder. But the law is not the cause of a 

 man's paying his taxes, nor is it the cause of his 

 abstaining from theft and murder. The law is simply 

 a statement of what will happen to a man if he does 

 not pay his taxes, and if he commits theft or murder ; 

 and the cause of his paying his taxes, or abstaining 

 from crime (in the absence of any better motive) is the 

 fear of consequences which is the effect of his belief 

 in that statement. A law of man tells what we may 

 expect society will do under certain circumstances; 

 and a law of nature tells us what we may expect 



