ii8 THE LIMITATIONS OF SCIENCE 



thetical method is generally applicable it is necessary 

 to explain gravitational action also as due to some 

 form of motion; Laplace has shown that the motion 

 involved requires a velocity many times that of light. 



Our most fundamental perception of an external 

 universe seems attainable from our sense perception of 

 force. The muscular sense of effort is apparently the 

 simplest and most general mechanical notion we have, 

 and in the opinion of the masters of the science our 

 idea of force is adequate to serve as the basis of so 

 exact a science as physics. Yet, when we attempt to 

 make force serve as a fundamental measure of phe- 

 nomena, we have found, since the time of Newton, that 

 it is not so convenient as mass and acceleration. Mo- 

 tion is further divisible into a measurement of length 

 and time. It is therefore customary to reduce all our 

 complex observations into combinations of the funda- 

 mental units of mass, length, and time instead of force. 

 The idea of force being thus associated in our minds as 

 an attribute of matter, we postulate the objective 

 reality and conservation of matter and assume the 

 fundamental attribute of matter to be its mass or 

 inertia. M. Hannequin expresses this idea clearly 

 when he says that nothing in a mechanical sense exists 

 except masses in motion. 



We shall next assume length, mass, and time to be 

 the fundamental units of measure. These quantities 

 are continuous or, at least, are indefinitely divisible. 



