288 PSYCHOLOGY. 



other optical sensations now absent, but wliich the present 

 sensations suggest. 



What, for example, is the slant-legged cross which we 

 think we see on the wall when we project the rectangular 

 after-image high up towards our right or left (Figs. 58 and 

 59) ? Is it not in very sooth a retinal sensation itself ? An 

 imagined sensation, not a felt one, it is true, but none the 

 less essentially and originally sensational or retinal for that, 

 — the sensation, namely, which we should receive if a ' real ' 

 slant-legged cross stood on the wall in front of us and threw 

 its image on our e3'e. That image is not the one our retina 

 now holds. Our retina now holds the image which a cross 

 of square shape throws when in front, but which a cross of 

 the slant-legged pattern wonid throw, provided it were 

 actually on the wall in the distant place at which we look. 

 Call this actual retinal image the ' square ' image. The 

 square image is then one of the innumerable images the 

 slant-legged cross can throw. Why should another one, 

 and that an absent one, of those innumerable images be 

 picked out to represent exclusively the slant-legged cross's 

 ' true ' shape ? Why should that absent and imagined 

 slant-legged image displace the present and felt square 

 image from our mind? Why, when the objective cross 

 gives us so many shapes, as it varies its position, should we 

 think we feel the true shape only when the cross is directly 

 in front? And when that question is answered, how can 

 the absent and represented feeling of a slant-legged figure 

 so successfully intrude itself into the place of a presented 

 square one ? 



Before answering either question, let us be doubly sure 

 about our facts, and see how true it is that in our dealings 

 ivith objects we ahoays do pick out one of the visual images they 

 yield, to constitute the real form or size. 



The matter of size has been already touched upon, so 

 that no more need be said of it here. As regards shape, 

 almost all the retinal shapes that objects throw are perspec- 

 tive ' distortions.' Square table-tops constantly present two 

 acute and two obtuse angles ; circles drawn on our wall- 

 papers, our carpets, or on sheets of paper, usually show like 

 ellipses ; parallels approach as they recede ; human bodies 



