238 HERMANN VON HELMHOLTZ 



established harmony and Locke's sensualism, and to which 

 Kant gave a decided turn in favour of the former doctrine '. 



Even at this time, and far more forcibly later, Helmholtz 

 declares himself in opposition to Kant, who affirmed that the 

 law of causation, as well as the intuition of time, and of tri- 

 dimensional space with its geometrical axioms, were of tran- 

 scendental origin, a priori ideas, innate in us. At the same 

 time Helmholtz was fully aware that his empiricist theory was, 

 and would remain, no more than a hypothesis. He believed, 

 however, that hypotheses are essential to action, and that every 

 man must choose for himself according to his own ethical or 

 aesthetic sense ; experiment alone, in which ' the chain of 

 causes runs through our self-consciousness ', can be regarded 

 critically, while observation, a process that ensues without our 

 connivance, may be modified by physical and psychical causes. 

 He was well aware that his hypothesis would meet with much 

 contradiction, and was not surprised when du Bois wrote to 

 him on April 28, 1868 : 



' The great objection to the strict empiricist attitude always 

 seems to me to be that it ought to be possible to carry it 

 through consistently, which, as you yourself admit, is not the 

 case ; for if it is innate in the calf to go after the smell of the 

 udder, why should not all its faculties be innate? It appears 

 to me that so much nativism which one cannot get rid of is 

 still left, that a handful more or less does not much matter. In 

 regard to motion, for example, there are countless complicated 

 cases in which we cannot get rid of it. You will say that one 

 can at least try to limit it as far as possible, and that I do not 

 deny. I must confess that on these points my craving for 

 causality is capable of greater resignation than yours.' 



Helmholtz subsequently answered all these objections in his 

 lecture ' On the Facts of Perception ', as follows : 



' To a great number of physiologists, whose views we might 

 term nativistic, in contrast to the empiricist which I have 

 myself endeavoured to defend, the conception of an acquired 

 knowledge of the field of vision appears untenable, because 

 they do not clearly realize what is so plain in the case of 

 speech, namely, how much the accumulated impressions of 

 memory can do. A number of different experiments have 

 accordingly been made with the intention of referring at 



