THE PERCEPTION OF SPACE. 277 



ous feelings combine. If we simply suppose that luminous sensations 

 per se feel extensive, our supposition is shattered by that influence of 

 movement in vision which is so clearly to be traced in many normal 

 errors in the measurement of the field of view. If we assume, on the 

 other hand, that the movements and their feelings are alone possessed 

 of the extensive quality, we make an unjustified hypothesis, for the 

 phenomena compel us, it is true, to accord an influence to movement, 

 but give us no right to call the retinal sensations indifferent, for there 

 are no visual ideas without retinal sensations. If then we wish rigor- 

 ously to express the given facts, we can ascribe a spatial constitution 

 only to combinations of retinal sensations with those of movement." 



Thus Wundt, dividing theories into ' nativistic ' and 

 * genetic,' calls his own a genetic theory. To distinguish it 

 from other theories of the same class, he names it a ' theory 

 of complex local signs.' 



" It supposes two systems of local signs, whose relations — taking the 

 eye as an example — we may think as . . . the measuring of the mani- 

 fold local-sign system of the retina by the simple local-sign system of 

 the movements. In its psychological nature this is a process of associa- 

 tive synthesis : it consists in the fusion of both groups of sensations 

 into a product, whose elementary components are no longer separable 

 from each other in idea. In melting wholly away into the product 

 which they create they become consciously undistinguishable, and the 

 mind apprehends only their resultant, the intuition of space. Thus 

 there obtains a certain analogy between this psj'chic synthesis and that 

 chemical synthesis which out of simple bodies generates a compound 

 that appears to our immediate perception as a homogeneous whole with 

 new properties." 



Now let no modest reader think that if this sounds ob- 

 scure to him it is because he does not know the full con- 

 text ; and that if a wise professor like Wundt can talk so 

 fluently and plausibly about ' combination ' and ' psychic 

 synthesis,' it must surely be because those words convey a 

 so much greater fulness of positive meaning to the scholar- 

 ly than to the unlearned mind. Keallj'' it is quite the re- 

 verse ; all the virtue of the phrase lies in its mere sound 

 and skin. Learning does but make one the more sensible of 

 its inward unintelligibility. Wundt's ' theory ' is the flim- 

 siest thing in the world. It starts by an untrue assump- 

 tion, and then corrects it by an unmeaning phrase. Retinal 

 sensations are spatial ; and were they not, no amount of 

 'synthesis' with equally spaceless motor sensations could 



