154 PSYCHOLOGY. 



contrasted in quality. If our two excited points awaken 

 identical qualities of sensation, they must, perforce, appear 

 to the mind as one ; and, not distinguished at all, they are, 

 a fortiori, not localized apart. Spots four centimetres dis- 

 tant on the back have no qualitative contrast at all, and fuse 

 into a single sensation. Points less than three thousandths 

 of a millimetre apart awaken on the retina sensations so 

 contrasted that we apprehend them immediately as two. 

 Now these unlikenesses which arise so slowly when we pass 

 from one point to another in the back, so much faster on 

 the tongue and finger-tips, but with such inconceivable 

 rapidity on the retina, what are they ? Can we discover 

 anything about their intrinsic nature ? 



The most natural and immediate answer to make is that 

 they are unlikeness of place pure and simple. In the words 

 of a German physiologist,* to whom psychophysics owes 

 much : 



" The sensations are from the outset {von vornherein) localized. . . . 

 Every sensation as such is from the very beginning affected with the 

 spatial quality, so that this quality is nothing like an external attribute 

 coming to the sensation from a higher faculty, but must be regarded as 

 something immanently residing in the sensation itself." 



And yet the moment we reflect on this answer an insu- 

 perable logical difiiculty seems to present itself. No single 

 quale of sensation can, by itself, amount to a consciousness 

 of position. Suppose no feeling but that of a single point 

 ever to be awakened. Could that possibly be the feeling 

 of any special ivliereyiess or tliereness ? Certainly not. Only 

 ivJien a second point is felt to arise can the first one acquire 

 a determination of up, doivn, right or left, and these determina- 

 tions are all relative to that second point. Each point, so far as 

 it is placed, is then only by virtue of what it is not, namely, 

 by virtue of another point. This is as much as to say that 

 position has nothing intrinsic about it ; and that, although a 

 feeling of absolute bigness may, a feeling of place cannot^ 

 possibly form an immaTwnt element in any single isolated sensa- 

 tion. The very writer we have quoted has given heed to 

 this objection, for he continues (p. 335) by saying that the 



* Vierordt, Grundriss der Physiologie, 5te Auflage (1877), pp. 326, 436. 



