ON THE PSYCHO-PHYSICAL VIEW OF NATURE. 469 



this section of scientific thought under the general term 

 of Psycho - physics. 1 It refers to the borderland or 

 common ground where physical and mental or psychical 

 phenomena meet or interact. 



Although the term psycho-physics is quite modern, the 

 idea of a special science dealing with the relations of 

 mind and body, or of the physical and mental life of the 

 human organism, has been prominently before the scien- 

 tific world ever since Cabanis published his celebrated 

 ' Eapports du Physique et du Moral de 1'Homme/ in 

 which the well-known passage occurs which has been 

 frequently repeated, modified, and quoted with varying 

 approval or reproach : 2 "In order to arrive at a correct 



4. 



Psycho- 



1 The term was first used by 

 G. T. Fechner in the well-known 

 work bearing this title, of which I 

 shall have more to say in the course 

 of the chapter. This work, deal- 

 ing mainly with a certain numerical 

 relation, narrowed the term down 

 to a special investigation, whereas 

 the larger problem, the study of 

 the interaction of mind and body 

 by the methods of the exact 

 sciences, was variously designated 

 as physiological psychology, mental 

 physiology, psycho - physiology or 

 physiology of the soul. As there 

 is a tendency to regard physiology 

 more and more as the physics of 

 the living organism, it is evident 

 that physics is the larger term ; and 

 in dealing with the relations of the 

 physical and the psychical in the 

 widest sense, the term psycho- 

 physics seems the more appropriate. 



2 ' CEuvres completes ' de Cabanis 

 (1834), vol. iii. p. 159. The simile 

 has attained a sort of historical 

 celebrity through the drastic ver- 

 sion which was given to it by Karl 

 Vogt in his ' Physiologische Briefe ' 

 (1847), p. 206, where, with a 



distinct intention of rousing an 

 aesthetic disapproval, he compares 

 the function of the brain with the 

 secretion of bile by the liver and 

 of urine by the kidneys. This 

 dictum, which he repeated in his 

 controversy with Rudolf Wagner, 

 led in the middle of the century, 

 as Du Bois-Reymond tells us, to a 

 kind of systematic championship of 

 the soul, the comparison with the 

 kidneys being looked on as a 

 degrading offence. " Physiology, 

 however, has no knowledge of such 

 grades of dignity. As a scientific 

 problem the secretion of the 

 kidneys is to her of the same 

 dignity as the investigation of the 

 eye or the heart or any other so- 

 called noble organ." Vogt used 

 the simile as an illustration of his 

 purely materialistic view. Lange 

 (' Hist, of Materialism," vol. ii. 

 p. 242) shows that with Cabanis 

 the dictum is by no means bound 

 up with such a view, as he really 

 was a pantheist. The mistake, 

 says Du Bois-Reymond, does not 

 lie in the comparison, but in the 

 implied suggestion, that psychical 



