PSYCHO-PHYSICAL METHOD 115 



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 depen- 

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

 between the bodily and the mental, the physical and 

 the psychical worlds.' Fechner, who first used the . 

 name psycho-physics and who is justly called the father 

 of the science, was led to undertake its foundation by 

 the desire to establish by the scientific method on an 

 empirical basis a certain view of the relation of the 

 physical to the psychical world, a view which he had 

 long held as an essential part of a speculative philo- 

 sophical system. 



Putting aside the extreme idealists, who would resolve 

 the physical universe that each man seems to see about 

 him into a construction of the mind that has no existence 

 save in the mind, we may recognize two great and 

 opposed doctrines of the relation of the physical to 

 the psychical. These two took definite form in the 

 seventeenth century, in the hands of Descartes and of 

 Spinoza respectively. Descartes's doctrine was dualistic. 

 He held that there are two fundamental substances or 

 enduring realities, matter and spirit, or extended sub- 

 stance and thinking substance that the two worlds 

 constituted of these two substances are for the most 

 part independent of one another, but that they come 

 together, have points of contact or interaction, in the 

 brains of men, this interaction giving rise to the conscious 

 life of man. 



Spinoza's doctrine, on the other hand, was monistic. 

 He taught that there is only one enduring substance 

 or ground of all appearances, and that this is revealed 



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