THE EXPLANATION OF LAWS 85 



developing our view further, it will be well to examine 

 the matter from another point of view. 



DIFFERENCE BETWEEN THEORIES AND LAWS 



It was stated before that it has been usually held that 

 the explanation of laws consists in showing that they are 

 particular examples of more general laws. If this view 

 were applied to the example under discussion, it might 

 be urged that the dynamical theory explains the properties 

 of gases because it shows that they are particular 

 examples of the laws of dynamics ; the properties of 

 gases are explained because they are shown to be the 

 consequences of the subjection of the molecules, of which 

 :ases consist, to the general laws of all moving bodies. 

 it might be said, is the clearest possible instance of 

 explanation by generalization, a simple extension of the 

 process involved in the discovery of laws. 



But, against this view, it must be pointed out that the 



most important feature of the theory is not that it states 



that molecules are subject to dynamical laws, but that 



which states that there are such things as molecules, and 



that gases are made up of them. It is that feature of the 



h makes it a real explanation. Now this 



fie theory is not a particular instance of any more 



general law ; indeed it is not a law or anything that could 



be an instance of a law. For it is not, according to the 



I down in Chapter II, part of the proper 



:natter on which scicinv builds its foundations. 



ings which we can see or i\v! ; tlu-v 



Mot, like the ordinary material bodies to which the 



wii to apply, objects di- 

 to direct percept inn. We only know i 



actually observe are gases, vary- 

 and it is only by these 

 pect the 



