52 PHYSIOLOGY. 



in like manner, take place from the different condition of the 

 nervous extremities, without any acrid matter applied. An- 

 other case which might be referred to this head, is that of the 

 amputated limb, where the sensation is referred to a place which 

 no longer exists ; and all the other instances where sensations 

 are referred to other places than those upon which the impres- 

 sion is made. (See LX.) 



" 2. With regard to the second head of the errors of sense 

 where the supposition of the external existence is well-founded, 

 but we judge of it otherwise than it really is if we admit the 

 philosophy of Bishop Berkley, we say, that the whole of the 

 supposition of external existence is purely ideal, that it is an 

 operation of the mind, and that the supposition of body is alto- 

 gether false. But even the sceptics, who do not carry matters 

 so far, allege that we have no certainty that, in any one 

 case, we do perceive external things such as they really are. 

 We can condescend upon many instances of our mistaking in 

 this respect, from which we might extend the possibility to the 

 whole. But we are not to be disturbed in the least by any subtle- 

 ties of this sort ; it is enough that we unavoidably suppose 

 and conclude the existence of body, and that we do distinguish 

 it in different cases by our different senses. This is the una- 

 voidable practice of the human mind ; and it is enough to say 

 that our perceptions are erroneous, where we perceive objects at 

 one time in a different manner from what we do at almost every 

 other, or where the perceptions of one sense do not correspond 

 to those of another. Thus, if I see a rod bent when im- 

 mersed in water, but upon applying my hand I feel it straight, 

 I know that my perception of its being crooked was erroneous. 

 In like manner, when the perception of a single man is dif- 

 ferent from that of a great number of others, this is called a 

 false judgment with regard to real objects. We may observe, 

 that the sceptics are almost quite in the right, when they ob- 

 serve that very constantly we make a false judgment in es- 

 tablishing the force of external impressions. In XLIII. I 

 was at pains to explain this matter, that our perceptions are 

 merely of the relative force. When these are as usual, our judg- 

 ment may be said to be as it ought to be in directing what 

 relates to our bodies ; but, in another respect, our sense is er- 





