THE PERCEPTION OF SPACE. 221 



Let us begin the long and rather tedious inquiry by the 

 most important case. Physiologists have long sought for 



spect to the self of the looker" (p. 345). But what constitutes the localiza- 

 tion of the Kernpunkt itself at any given time, except ' Experience,' i.e., 

 higher cerebral and intellectual processes, involving memory, Hering does 

 not seek to define. 



Stumpf, the other sensationalist writer who has best realized the diffi- 

 culties of the problem, thinks that the primitive sensation of distance 

 must have an immediate physical antecedent, either in the shape of "an 

 organic alteration accompanying the process of accommodation, or else 

 given directly in the specific energy of the optic nerve." In contrast i^ith 

 Hering, however, he thinks that it is the absolute distance of the spot 

 fixated which is thus primitively, immediately, and physiologically given, 

 and not the relative distances of other things about this spot. These, he 

 thinks, are originally seen in what, broadly speaking, may be termed one 

 plane with it. Whether the distance of this plane, considered as a phe- 

 nomenon of our primitive sensibility, be an invariable datum, or su3cepti- 

 ble of fiuctuatiou, he does not, if I understand him rightlj^, undertake 

 dogmatically to decide, but inclines to the former view. For him then, 

 as for Hering, higher cerebral processes of association, under the name of 

 ' Experience,' are the authors of fully one-half part of the distance-percep- 

 tions which we at any given time maj' have. 



Hering's and Stumpf's theories are reported for the English reader by 

 Mr. Sully (in Mind, in. pp. 172-6). Mr. Abbott, in his Sight and Touch 

 (pp. 96-8), gives a theory which is to me so obscure that I only refer the 

 reader to its place, adding that it -seems to make of distance a fixed func- 

 tion of retinal sensation as modified by focal adjustment. Besides these 

 three authors I am ignorant of any, except Pan um, who may have attempt- 

 ed to define distance as in any degree an immediate sensation. And with 

 them the direct sensational share is reduced to a very small proportional 

 part, in our completed distance-judgments. 



Profes.sor Lipps, in his singularly acute Psychologische Studien (p. 69 

 ff.),argues, as Ferrier, in his review of Berkeley (Philosophical Remains, ii. 

 330 H.), had argued before him, that it is loqicnlly impossible we should 

 perceive the distance of an^^hing from the eye by sight: iov ?,seen distance 

 can only be between seen termini ; and one of the termini, in the case of dis- 

 tance from the eye, is the eye itself, which is not seen. Similarly of the 

 distance of two points behind each other : the near one 7«(^es the far one, 

 no space is seen between them. For the space between two objects to be 

 seen, both must appear beside each other, then the space in ({ueslion will be 

 visible. On no other condition is its visibility possible. The conclu.sion is 

 that things can properly be seen only in what Lipps calls a surface, and 

 that our knowledge of the third dimension must needs be conceptual, not 

 sensational or visually intuitive. 



But no arguments in the world can prove a feeling which actually 

 exists to be impossible. The feeling of depth or distance, of farness or 

 awayness, does actually exist as a fact of our visual sensibilit}'. All that 

 Professor Lipps's reasonings prove concerning it is that it is not linear ia 



