OF NATURAL PHILOSOPHY. 91 



gation of matter resolves itself into the general 

 question, What will be the behaviour of material 

 particles under the mutual action of opposing 

 forces capable of counterbalancing each other? 

 and the answer to this question can be no other 

 than the announcement of the law of equilibrium, 

 whatever law that may be. 



(82.) With regard to the cause of sensation, it 

 must be regarded as much more obscure ,than that 

 of motion, inasmuch as we have no conscious know- 

 ledge of it, i. e. we have no power, by any act of 

 our minds and will, to call up a sensation. It is 

 true, we are not destitute of an approach to it, 

 since, by an effort of memory and imagination, we can 

 produce in our minds an impression, or idea, of a 

 sensation which, in peculiar cases, may even ap- 

 proach in vividness to actual reality. In dreams, too, 

 and, in some cases of disordered nerves, we have 

 sensations without objects. But if force, as a cause 

 of motion, is obscure to us, even while we are in the 

 act of exercising it, how much more so is this 

 other cause, whose exercise we can only imitate 

 imperfectly by any voluntary act, and of whose 

 purely internal action we are only fully conscious 

 when in a state that incapacitates us from reasoning, 

 and almost from observation ! 



(83.) Dismissing, then, as beyond our reach, the 

 enquiry into causes, we must be content at present 

 to concentrate' our attention on the laws which pre- 

 vail among phenomena, and which seem to be their 

 immediate results. From the instance we have just 

 given, we may perceive that every enquiry into the 

 intimate nature of a complex phenomenon branches 



