134 INTRODUCTION TO SCIENCE 



of simplification, and that is true. "Heat** 

 and "Light" have yielded to simplifying analysis; 

 perhaps "Chemical Affinity" is at present yield- 

 ing; perhaps the physicist may some day discover 

 the true inwardness of Gravitation, and be able 

 to tell us what really happens in the invisible 

 world when the apple falls in the orchard. It is 

 the aim of Science to reduce the number of abso- 

 lutely necessary concepts, but it does not in so 

 doing make those that remain any simpler. 

 "Matter" and "Energy" or other terms of the 

 same order of magnitude are always, as it were, 

 expanding as others are forced into them, and 

 remain as fundamental terms which are not self- 

 explanatory. 



Taking "matter," for instance, which has 

 seemed to some the most trustworthy bedrock 

 on which to base their theoretical reconstruction 

 of the world, what a visionary thing it has become 

 in the hands of modern physics. The founders 

 f the molecular theory laid down the idea that 

 each kind of matter has its characteristic kind of 

 particle; Dalton showed that we must think of 

 tiiese molecules as built up of atoms; modern 

 work is suggesting that there may be a common 

 basis for matter of all kinds, as if the different 

 kinds of atoms consisted of different numbers of 

 smaller corpuscles of the same kind. These are 

 tke negatively electrified particles the corpuscles 



