4 CROONIAN LECTURES 



materialism, and it may be marked as the 

 transition or Newtonian stage. 



The third stage rests solely on the advance 

 of natural knowledge, and is characterised by 

 the complete union or perfect inseparability 

 between the ideas of ponderable matter and 

 force. This may be called materialism, if, in 

 the definition of matter, the definition of force 

 is included ; or it may be called spiritualism, 

 if, in the definition of spirit, the definition of 

 matter is contained. This stage, in which our 

 ideas of ponderable matter and force are in- 

 separably united, may be distinguished as the 

 modern stage. 



The first or primitive stage is that of com- 

 plete separation between the ideas of matter 

 and force. 



Before bringing to your notice some of the 

 records of this stage which exist, it is desirable 

 that you should for a moment consider what the 

 earliest ideas of matter and force were likely 

 to be when no knowledge of science existed. 



The further we go back, the more we must 

 expect ideas of force and matter to be formed 

 on superficial likenesses and distinctions. Scien- 



