CHAPTER L 



THE EELATIVITY OF KNOWLEDGE. 



When we contemplate any portion of matter, such as a 

 cubical block of metal or wood, it appears to our senses to be 

 perfectly solid. No breach of continuity appearing anywhere 

 among the aggregate of visual and tactual perceptions which 

 its presence awakens in us, we are unable to restrain ourselves 

 from imagining that its parts are everywhere in actual contact 

 with each other. Nevertheless, a brief analysis of this opinion 

 will suffice to show that it cannot be maintained without 

 landing us in manifest absurdity. We need only recollect 

 that every portion of matter is compressible, — may be made 

 to occupy less space than before, — and that compressibility, 

 implying the closer approach of the constituent particles of 

 the body, is utterly out of the question, unless empty space 

 exists between these particles. We are therefore obliged to 

 admit that the molecules of which perceptible matter is com- 

 posed, are not in immediate contact, but are separated from 

 each other by enveloping tracts of unoccupied space. 



But no sooner do we seek refuge in this assumption than 

 we are again met by difficulties no less insuperable than the 

 one just noticed. The form of our experience of all objects 

 compels us to postulate that cohesive or gravitative forces 

 are continually urging the particles of matter toward closer 



B 2 



