PROFESSOR IN BERLIN 305 



spiritualist theory, that his Critique of Pure Reason was a per- 

 petual protest against the use of categories of thought beyond 

 the limits of experience, and that he detected a tissue of false 

 conclusions in all metaphysical systems. But inasmuch as 

 Kant regarded the axioms of geometry as derived from pure 

 transcendental intuition, pure a priori intuition had become the 

 refuge of metaphysicians, and the expression of this theory in 

 physiology is the nativist theory. Hence comes the great im- 

 portance of experiment, to resolve the pure or empirical con- 

 cepts, the axioms of geometry, the fundamental laws of mechanics, 

 or the modes of visual perception, into their rational elements. 

 He warns the younger men of science not to be led away by 

 the fact that all sects of metaphysicians are up in arms against 

 it, ' since these investigations put the axe to what seems to be 

 the strongest support still left to their claims/ Materialism to 

 Helmholtz is, equally, a metaphysical hypothesis, which may 

 sometimes have proved profitable to the natural sciences, but 

 can, as a dogma, be as great a hindrance to the progress of 

 knowledge. 



' Memory, experience, practice, are also facts, the laws of 

 which can be investigated, and which cannot be decreed away, 

 even if they are not to be smoothly and simply referred to the 

 known laws of excitation and conductivity in nerve fibres, 

 however pretty a playground for fancy may be afforded by the 

 ramification of the ganglion processes and nervous connexions 

 in the brain/ 



Helmholtz was shaken and wearied in mind and body by the 

 death of his daughter Kathe, and his incessant scientific work ; 

 he also felt many worries brought on him by envy and malice 

 more keenly than of yore. His wife, who was at that time 

 with her children on the Starnberger See, was his comforter 

 in the best sense : 



1 1 sit and dream for hours, and think of you, my dear, and 

 wish you were here and free from all miseries. Nature is a 

 great teacher, even in matters in which she has otherwise 

 little enough to do. She brings out the relative value of things 

 so plainly/ 



In the above lecture he had cautioned his pupils : ' One word 

 more. I would not have you think my point of view affected by 

 my personal experience. That any one, holding such opinions 



