ii 4 PSYCHO-PHYSICAL METHOD 



physical and the psychical, were in no way connected or 

 related. 



But, although science treated them as unrelated, it had 

 long been clear to all men that the two orders of events, 

 the physical and the psychical, are in some way intimately 

 related. Nothing is more certain or more obvious. A 

 solid body strikes sharply against your hand and you 

 at once experience pain, a ray of sunlight falls on your 

 face and you at once experience sensations of light and 

 warmth, or you feel hungry and at once stretch out your 

 hand to take food, you feel pain or discomfort and you 

 at once move your limbs in order to get rid of it. We 

 observe, in fact, a constant concurrence or concomitance of 

 events of the two orders, the physical and the psychical, 

 and this constant concomitance leads even the most 

 unreflecting man to assume some orderly relation between 

 them. 



The fact of the 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 the psychical worlds, remained a subject 

 of speculation only until long after the scientific method 

 had been applied with success to each of these realms 

 independently. In fact, it was not until the middle of 

 the nineteenth century 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 psychical and the physical. 



This step was taken, and this new branch of science 

 was founded, by Gustav Theodor Fechner, Professor of 



