ON THE PSYCHO-PHYSICAL VIEW OF NATURE. 491 



these Helmholtz is led into aesthetical and psychological 

 discussions, clearly distinguishing between such principles 

 as are inherent in natural, physical, and physiological 

 relations, and such others as depend on the inventions of 

 genius and the gradual changes brought about by exter- 

 nal requirements and ingrained by habit and education. 1 

 The physiology of seeing had yet more remarkable 

 consequences for the history of Thought. We may say 

 that through Helmholtz's analysis of the formation of 

 our space perceptions by the eye in connection with the 

 tactile and muscular senses, psychology and metaphysics 

 were brought into immediate contact with physics and 

 physiology. It is here that Helmholtz takes up an IT. 



Helmholtz 



entirely different, and, previously, isolated line of reason- and Kant, 

 ing, which centres in Kant's theory of space and time as 

 innate forms of perception the so-called subjectivity or 

 ideality of time and space. The studies of this subject 

 had been somewhat prepared by the writings of Herbart 

 and Lotze. The teachings of Kant have had an influence 

 in the direction indicated through two distinct channels, 

 through Johannes Miiller's Physiology and through 

 Herbart's Psychology : the latter seems to have had 



1 See the closing words of the 

 13th chapter of Helmholtz's work : 

 " As the fundamental principle for 

 the clevelopement of the European 

 tonal system, we shall assume that 

 the whole mass of tones and the 

 connection of harmonics must stand 

 in a close and always distinctly 

 perceptible relationship to some 

 arbitrarily selected tonic, and that 

 the mass of tone which forms the 

 whole composition must be de- 

 veloped from this tonic, and must 

 finally return to it. The ancient 

 world developed this principle in 



homophonic music, the modern 

 world in harmonic music. But it 

 is evident that this is merely an 

 acsthetical principle, not a natural 

 law. The correctness of this prin- 

 ciple cannot be established a priori. 

 It must be tested by its results. 

 The origin of such testhetical prin- 

 ciples should not be ascribed to a 

 natural necessity. They are the 

 inventions of genius, as we pre- 

 viously endeavoured to illustrate 

 by a reference to the principles of 

 architectural style." 



