SENSATION AND SENSIFEROUS ORGANS. 95 



but those of smell and hearing, we should be unable to conceive a ma- 

 terial substance. We might have a conception of time, but could have 

 none of extension, or of resistance, or of motion. And without the 

 three latter conceptions no idea of matter could be formed. Our whole 

 knowledge would be limited to that of a shifting succession of immate- 

 rial phenomena. But, if an immaterial substance may exist, it may 

 have any conceivable properties ; and sensation may be one of them. 

 All these propositions may be affirmed with complete dialectic safety, 

 inasmuch as they can not possibly be disproved ; but neither can a par- 

 ticle of demonstrative evidence be offered in favor of them. 



As regards the second hypothesis, it certainly is not inconceivable, 

 and therefore it may be true, that sensation is the direct effect of certain 

 kinds of bodily motion. It is just as easy to suppose this as to suppose, 

 on. the former hypothesis, that bodily motion affects an immaterial sub- 

 stance. But neither is it susceptible of proof. 



And, as to the third hypothesis, since the logic of induction is in no 

 case competent to prove that events apparently standing in the relation 

 of cause and effect may not both be effects of a common cause that 

 also is as safe from refutation, if as incapable of demonstration, as the 

 other two. 



In my own opinion, neither of these speculations can be regarded 

 seriously as anything but a more or less convenient working hypothesis. 

 But, if I must choose among them, I take the " law of parcimony " for 

 my guide, and select the simplest namely, that the sensation is the 

 direct effect of the mode of motion of the sensorium. It may justly be 

 said that this is not the slightest explanation of sensation ; but then 

 am I really any the wiser, if I say that a sensation is an activity (of 

 which I know nothing) of a substance of mind (of which also I know 

 nothing) ? Or, if I say that the Deity causes the sensation to arise in 

 my mind immediately after he has caused the particles of the sensorium 

 to move in a certain way, is anything gained ? In truth, a sensation, 

 as we have already seen, is an intuition a part of immediate knowl- 

 edge. As such it is an ultimate fact and inexplicable ; and all that we 

 can hope to find out about it, and that indeed is worth finding out, is 

 its relation to other natural facts. That relation appears to me to be 

 sufficiently expressed, for all practical purposes, by saying that sensa- 

 tion is the invariable consequent of certain changes in the sensorium 

 or, in other words, that, so far as we know, the change in the sensorium 

 is the cause of the sensation. 



I permit myself to imagine that the untutored, if noble, savage of 

 common sense who has been misled into reading thus far by the hope 

 of getting positive solid information about sensation, giving way to not 

 unnatural irritation, may here interpellate : " The upshot of all this 

 long disquisition is, that we are profoundly ignorant. We knew that 

 to begin with, and you have merely furnished another example of the 

 emptiness and uselessness of metaphysics." But I venture to reply, 



