24 o HERMANN VON HELMHOLTZ 



ments are a priori easier than others is conceivable ; this may 

 be the case with the eye-movements also. But to speak of 

 compulsion in these instances is beside the mark. All that 

 I desire is proof that there is a natural disposition in favour of 

 these movements. 



' With all this confounded trafficking in hypotheses about 

 invisible nervous associations, with all manner of inconceivable 

 properties, which have checked the progress of the physiology of 

 the central nervous system for so many }^ears, I do believe it 

 to be most important to open people's eyes to the number of 

 superfluous hypotheses which they are making, and would 

 rather exaggerate the opposite view, if need be, than proceed 

 along these false lines. Reflex motion may at present be 

 defined as everything in physiology which we can't explain. 

 These are the disadvantages of an exaggerated materialistic 

 metaphysic, from which people must be brought back to facts/ 



Precisely because Helmholtz wanted to weaken the objections 

 raised to his hypothesis on account of the existence of sensory 

 illusions, he laid down as a rule in all illusions, that we always 

 think we see such objects before us as would have to be 

 present in order to bring about the same retinal images under 

 normal conditions of observation ; and he chose the name of 

 unconscious inference for these processes, in which words are 

 replaced by sensations and memory images, although these 

 involve the same intellectual activity as the ordinary inferences. 

 Even the supporters of the nativistic theory must, he insists, 

 admit that the peculiar completeness and refinement of sensory 

 intuition depend upon experience. 



When Helmholtz was pursuing his acoustic researches upon 

 the aesthetic side of sensations of tone, he proved that the 

 forms of musical configuration depend more strictly than in the 

 case of any other art upon the nature and idiosyncracies of our 

 sensations. And in the lectures which he gave at Berlin, 

 Dusseldorf, and Cologne, 1871-1873, on The Relation of Optics 

 to Painting, he succeeded in establishing for painting (in 

 which the nature of the material to be employed and of the 

 objects to be represented have far more influence, though here 

 too the specific sensibility of the visual organ is not without 

 significance) that it is not only profitable for physiological 

 optics that attentive consideration should be given to the works 



