282 PSYCHOLOGY. 



fore we can only apprehend it at all by having unconsciously 

 summed these up in our head. It is the old idea of our 

 actual knowledge being drawn out from a pre-existent 

 potentiality, an idea which, whatever worth it may meta- 

 physically possess, does no good in psychology. 



My own sensationalistic account has derived most aid 

 and comfort from the writings of Hering, A. W. Volkmann, 

 Stumpf, Leconte, and Schuu. All these authors allow 

 ample scope to that Experience which Berkeley's genius 

 saw to be a present factor in all our visual acts. But they 

 give Experience some grist to grind, which the soi-distant 

 ' empiristic ' school forgets to do. Stumpf seems to me the 

 most philosophical and profound of all these writers ; and 

 I owe him much. I should doubtless have owed almost as 

 much to Mr. James Ward, had his article on Psychology in 

 the Encyclo]3?edia Britannica appeared before my own 

 thouglits were written down. The literature of the question 

 is in all languages very voluminous. I content myself with, 

 referring to the bibliography in Helmholtz's and Aubert's 

 works on Physiological Optics for the visual part of the 

 subject, and with naming in a note the ablest works in the 

 English tongue which have treated of the subject in a gen- 

 eral way.* 



* G. Berkeley : Essay towards a new Theory of Vision ; Samuel Bailey r 

 A Review of Berkeley's Theory of Visiou (1842) ; J. S. Mill's Review of 

 Bailey, in his Dissertations and Disquisitions, vol. ii ; Jas. Ferrier : Re- 

 view of Bailey, in 'Philosophical Remains,' vol. ii ; A. Bain : Senses and 

 Intellect, 'Intellect,' chap, i ; H. Spencer: Principles of Psj^hology, pt. 

 VI. chaps. XIV, XVI ; J. S. Mill : Examination of Hamilton, chap, xiii 

 (the best statement of the so-called English empiricist position) ; T. K. 

 Abbott : Sight and Touch, 1861 (the first English book to go at all mi- 

 nutely inio facts ; Mr. Abbott maintaining retinal sensations to be originally 

 of space in three dimensions) ; A. C. Eraser : Review of Abbott, in North 

 British Review for Aug. 1864 ; another review in Macmillan's Magazine, 

 Aug. 1866 ; J. Sully : Outlines of Psychology, chap, vr ; J. Ward : En- 

 cyclop. Britannica, 9th Ed., article ' Psychology,' pp. 53-5 ; J. E. Walter; 

 The Perception of Space and Matter (1879) —I may also refer to a ' discus- 

 sion ' between Prof. G. Croom Robertson, Mr. J. Ward, and the present 

 writer, in Mind, vol. xiii. — The present chapter is only the tilling out with 

 detail of an article entitled 'The Spatial Quale,' which appeared in the 

 Journal of Speculative Philosophy for January 1879 (xiii. 64). 



