SCIENCE AND PHILOSOPHY 159 



relation has therefore always been recognized 

 since men first began to reflect. But the nature 

 of this relation that so clearly obtains between the 

 physical and psychical worlds remained a sub- 

 ject of speculation only until long after the scien- 

 tific method has been applied with success to 

 each of these realms independently. In fact, it 

 was not until the middle of the nineteenth cen- 

 tury that the scientific method was brought to 

 bear upon the problem of the nature of this 

 relation; and it was this, the application of the 

 scientific method to this problem, that led to 

 the development of that youngest branch of 

 science known as psycho-physics. 



"For psycho-physics may be broadly defined 

 as the application of the scientific method to the 

 investigation of the relation between the psy- 

 chical and the physical. This step was taken, and 

 this new branch of Science was founded, by 

 Gustav Theodor Fechner, Professor of Physics 

 at Leipzig, with full consciousness of the nature 

 and importance of the step. In his celebrated 

 work, Elemente der Psycho-physik, published in 

 1860, Fechner says: 'By psycho-physics is to be 

 understood an exact study of the functional 

 relations, or relations of dependence, between 

 body and soul, or, in more general terms, between 

 the bodily and the mental, the physical and the 

 psychical worlds." (See MacDougall: "Psycho- 



