THE PERCEPTION OF SPACE. 157 



And now let us revert to the query propounded a. 

 moment since : Can these differences of mere quality in feeling^ 

 varying accoirling to locality yet having each sensibly and in- 

 trinsically and by itself nothing to do ivith position, constitute 

 the ^susceptibilities'' ice mentioned, the conditions of being per- 

 ceived in position, of the localities to ivhich they belong ? The 

 numbers on a row of houses, the initial letters of a set of; 

 words, have no intrinsic kinship with points of space, and 

 yet they are the conditions of our knowledge of where any 

 house is in the row, or any word in the dictionary. Can the 

 modifications of feeling in question be tags or labels of this 

 kind which in no wise originally reveal the position of the 

 spot to which they are attached, but guide us to it by what 

 Berkeley would call a ' customary tie ' ? Many authors have 

 unhesitatingly replied in the affirmative ; Lotze, who in his. 

 Medizinische Psychologie* first described the sensations in. 

 this way, designating them, thus conceived, as local-signs. 

 This term has obtained wide currency in Germany, and in 

 speaking of the ' local-sign theoky ' hereafter, I shall always 

 mean the theory ivhich denies that there can he in a sensation any 

 element of actual locality, of inherent spatial order, any tone as 



schen- u. Thierseele, i. 214) called attention to the changes of colorsensibllity- 

 which the retina displays as the image of the colored object passes f roni the 

 fovea to the periphery. The color alters and becomes darker, and the 

 change is more rapid in certain directions than in others. This alteration 

 in general, however, is one of which, as such, we are wholly unconscious. 

 We see the sky as bright blue all over, the modifications of the blue sensa- 

 tion being interpreted by us, not as differences in the objective color, but 

 as distinctions in its locality. Lotze (Medizinische Psychologic, 333. 355), ori 

 the other hand, has pointed out the peculiar tendency which each particu- 

 lar point of the retina has to call forth that movement of the eyeball which 

 will carry the image of the exciting object from the point in question to 

 the fovea. With each separate tendency to movement (as with each actual 

 movement) we may suppose a peculiar modification of sensibility to be 

 conjoined. This modification would constitute the peculiar local tingeing 

 of the image by each point. See also Sully's Psychology, pp. 118-121. 

 Prof. B. Erdman has quite lately (Vierteljahrsschrift f. wiss. Phil., x. 

 324-9) denied the existence of all evidence for such immanent qvalia of 

 feeling characterizing each locality. Acute as his remarks are, they quite 

 fail to convince me. On the skin the qvalia are evident, 1 should .say- 

 Where, as on the retina, they are less so (Kries and Auerbach), this may- 

 well be a mere difficulty of discrimination not yet educated to the 

 analysis. 



* 1852, p. 331. 



