The Science of the Mind 547 



physiological concomitants, it is clear that these physiological 

 concomitants, namely the molecular changes in the nerve-centre, 

 would, if completely ascertained, afford an accurate index of the 

 mental processes." 



But no one has ever shown what the chemical or mechanical 

 changes are by which thought and feeling are produced. Mech- 

 anism, as applied to mind, remains a mere hypothesis, an 

 hypothesis, it may be added, to which philosophy gives no support. 



Another view is that mind is a separate existence. The rela- 

 tion of the mind to body is, on this view, frequently held to be one 

 of parallelism: the two series, mental and physical, are indepen- 

 dent of each other, each runs its own course, "as two railway trains 

 running side by side on a double track, or two rays of light pro- 

 jected towards the same infinitely distant point, run parallel with 

 one another in time and space." There is no cross effect from one 

 to the other; each is a closed system, with its own laws. When 

 consistently held, this view does not carry us much farther than 

 the first view; each point in the mental series must have its 

 counterpart in the physical series; the laws that are established 

 for the physical must also account for the psychical events. 



A third view is Animism, the Soul-theory, the belief that there 

 is an individual mind in each living animal body; that be- 

 tween the mind and its organism a vital relationship holds; that 

 the life processes are both mental and physical ; that the directing 

 force in evolution is to be found in the minds of the individual 

 organisms, the urge of feeling in the lower, the increasing 

 strength of emotion and will, with the widening scope of interest 

 and of thought, in the higher organisms. Many arguments can 

 be brought forward both for and against this theory, but we can- 

 not discuss these here. 



There has also been much discussion of what is called The 

 Two-Aspect Theory, to which biological facts incline many in- 

 quirers. The theory assumes a psycho-physical being a reality 

 which we know under two aspects; 



