THE PERCEPTION OF SIGHT. 311 



do so by looking as that major proposition states. This 

 perception of what I am doing is my minor proposition, 

 and the ' conclusion^ is that the object I am looking for 

 will be found at the spot in question. 



Suppose that I employ the same way of looking, but look 

 into a stereoscope. I am now aware that there is no real 

 object before me at the spot I am looking at ; but I have the 

 same sensible impression as if one were there ; and yet I 

 am unable to describe this impression to myself or others, 

 or to characterise it otherwise than as ' the same impression 

 which would arise in the normal method of observation, if 

 an object were really there.' It is important to notice this. 

 No doubt the physiologist can describe the impression 

 in other ways, by the direction of the eyes, the position 

 of the retinal images, and so on ; but there is no other 

 way of directly defining and characterising the sensation 

 which we experience. Thus we may recognise it as an 

 illusion, but yet we cannot get rid of the sensation of this 

 illusion ; for we cannot extinguish our remembrance of 

 its normal signification, even when we know that in the 

 case before us this does not apply — just as little as we 

 are able to drive out of the mind the meaning of a 

 word in our mother tongue, when it is employed as a 

 sign for an entirely different purpose. 



These conclusions in the domain of our sensible per- 

 ceptions appear as inevitable as one of the forces of 

 nature, and hence their results seem to be directly ap- 

 prehended, without any effort on our part ; but this 

 does not distinguish them from logical and conscious 

 conclusions, or at least from those which really deserve 

 the name. All that we can do by voluntary and con- 

 scious effort, in order to come to a conclusion, is, after 

 all, only to supply complete materials for constructing the 

 necessary premisses. As soon as this is done, the conclu- 

 sion forces itself upon us. Those conclusions which (it is 



