26 ORIGIN OF PHYSICAL CONCEPTS 



by spatial representations. These must be derived 

 from touch. What, then, can be the spatial repre- 

 sentations which arise from touch ? The blind, he 

 says, are often asked, How do you figure to your- 

 self such and such an object, a chair, a table, a 

 triangle ? M. Villey quotes Diderot as affirming 

 that the blind cannot imagine. According to 

 Diderot, images require colour, and colour being 

 totally wanting to the blind the nature of their 

 imagination was to him inconceivable. The 

 common opinion, says M. Villey, is entirely with 

 Diderot. It does not believe that the blind can 

 have images of the objects around him. The 

 photographic apparatus is awanting and the photo- 

 graph cannot therefore be there. 



Diderot was a sensationalist. For this school, 

 as Villey remarks, V image est le decalque de la sensa- 

 tion, and he refers not merely to Condillac the 

 friend of Diderot but to his continuator Taine 

 whose dictum we have already quoted. 



Diderot attempts to solve the problem by main- 

 taining that tactual sensations occupy an extended 

 space which the blind in thought can add to or 

 contract, and in this way equip himself with spatial 

 conceptions. 



There would, on this view, as M. Villey remarks, 

 be a complete heterogeneity between the imagina- 



