MATTER AND FOKCE AS CAUSES. 253 



matter, teaches us that matter, as a cause, has matter for its 

 effect ; but we are equally justified in saying that to force as 

 cause, corresponds force as effect. Since c=e, and e=c, it 

 is unnatural to call one term of an equation a force, and the 

 other an effect of force or phenomenon, and to attach differ- 

 ent notions to the expressions Force and Phenomenon. In 

 brief, then, if the cause is matter, the effect is matter ; if the 

 cause is a force, the effect is also a force. 



A cause which brings about the raising of a weight is a 

 force ; its effect (the raised weight) is, accordingly, equally a 

 force ; or, expressing this relation in a more general form, 

 separation in space of ponderable objects is a force ; since this 

 force causes the fall of bodies, we call it falling force. Fall- 

 ing force and fall, or, more generally still, falling force and 

 motion, are forces which are related to each other as cause 

 and effect forces which are convertible one into the other 

 two different forms of one and the same object. For exam- 

 ple, a weight resting on the ground is not a force : it is neither 

 the cause of motion, nor of the lifting of another weight ; it 

 becomes so, however, in proportion as it is raised above the 

 ground : the cause the distance between a weight and the 

 earth and the effect the quantity of motion produced beai 

 to each other, as we learn from mechanics, a constant rela- 

 tion. 



Gravity being regarded as the cause of the falling of bod- 

 ies, a gravitating force is spoken of, and so the notions of 

 property and of force are confounded with each other : pre- 

 cisely that which is the essential attribute of every force 

 the union of indestructibility with convertibility is wanting 

 in every property : between a property and a force, between 

 gravity and motion, it is therefore impossible to establish the 

 equation required for a rightly-conceived causal relation. If 

 gravity be called a force, a cause is supposed which produces 

 effects without itself diminishing, and incorrect conceptions 

 of the causal connections of things are thereby fostered. In 



