446 The Theory of Aether and Electrons in the 



Of the events with which Natural Philosophy is concerned, 

 each is perceived to happen at some definite location at some 

 definite moment. When a material object has been observed 

 to occupy a certain position at a certain instant, the same 

 object may again be observed at a subsequent instant ; but it 

 is impossible to determine whether the object is or is not in 

 the same position, since there is no obvious means of preserving 

 the identity of any location from one moment to another. 

 The physicist, however, finds it convenient to construct a 

 framework of axes in space and time for the purpose of fitting 

 his experiences into an orderly arrangement ; and the ques- 

 tion at issue is whether experience furnishes the means of 

 determining a framework completely and uniquely by 

 absolute properties, or whether the selection inevitably rests 

 on arbitrary choice and accidental circumstance. 



In attempting to answer this question, it may first be 

 observed that the choice is always made so as to simplify 

 the description of natural phenomena as much as possible ; 

 thus, the variable which is to measure time is so chosen that 

 its increment in the interval between any two consecutive 

 beats of a pendulum is the same as its increment in the interval 

 between any other two consecutive beats. If the selection of 

 the four variables (x, y, z y t) is well made, it should be possible 

 to express the laws of nature by statements of a simple character, 

 e.g., that a body isolated from the influence of external agents 

 moves through equal intervals of space in equal intervals of 

 time. 



Accepting, then, the principle that the framework of axes 

 is to be chosen so as to furnish the simplest possible expression 

 of the natural laws, it becomes of importance to determine 

 which of the natural laws are entitled, by reason of their 

 primary importance, to receive the greatest consideration. 



Now many indications point to the probability that the 

 various types of forces which are observed in ponderable 

 bodies forces of cohesion, of chemical union, and so forth 

 are ultimately electric in their nature. Such an assumption 



