Art. I. — On Force. 

 By F. J. PiRANi, M.A. 



[Read 12th April, 1877.] 



The nature of our conception of Force and of Force itself, 

 if there be any such thing, have been the matter of frequent 

 discussion ; but the various questions raised cannot be said 

 to have received answers which are universally accepted as 

 satisfactory. 



Why does a stone fall to the ground if unsupported ? 

 It is stated in explanation of this phenomenon that the 

 stone is attracted by the earth, or that the earth exerts 

 a force upon it. What do we mean in the first place 

 by saying that a force is exerted upon the stone ; and 

 secondly, by saying that that force is exerted by the earth ? 

 Had we said that the motion of the stone was due to a force 

 exerted by John Smith, the meaning of such a statement is 

 plain enough — that a certain state or act of John Smith's 

 mind, such as we call an effort, pull, or force, preceded and 

 was the cause of the motion. Do we mean, then, in the 

 former case, that a similar state of consciousness, a similar 

 effort or pull, was antecedent to the motion of the stone ? 

 and if so, do we imagine the earth to be a being capable of 

 exerting such pulls ? As a matter of analytical convenience 

 it is doubtless extremely useful to imagine inanimate bodies 

 'as exerting efforts to move each other about, similar to the 

 forces which each man knows that he exerts himself, and 

 which he believes to be exerted by other human beings ; but 

 do they really do so ? I follow the system of philosophy 

 which Mr. G. H. Lewes is now expounding, so far at all 

 events as to reply that we have no means of ascertaining 

 whether they really do or not ; that the idea of forces sup- 

 posed to be exerted by inanimate bodies is a metempirical 

 concept, indispensable perhaps for purposes of calculation, 

 but resembhng subsidiary unknowns introduced in the 

 course of solving a mathematical problem^ which disappear 

 in the final result. 



The effects of which the forces are supposed to be the 



