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 

 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 Mliller's Physiology and through 

 Herbart's Psychology : the latter seems to have had 



1 See the closing words of the homophonic music, the modern 



13th chapter of Helmholtz's work : world in harmonic music. But it 

 " As the fundamental principle for i is evident that this is merely an 

 the development of the European i sesthetical principle, not a natural 



tonal system, we shall assume that law. The correctness of this prin- 



the whole mass of tones and the ciple cannot be established a priori. 



connection of harmonics must stand It must be tested by its results. 



in a close and always distinctly The origin of such sesthetical prin- 



perceptible relationship to some ciples should not be ascribed to a 



arbitrarily selected tonic, and that natural necessity. They are the 



the mass of tone which forms the inventions of genius, as we pre- 



whole composition must be de- viously endeavoured to illustrate 



veloped from this tonic, and inu.-t by a reference to the principles of 



finally return to it. The ancient architectural style." 

 world developed this principle in 



