496 SCIENTIFIC THOUGHT. 



all liberated them from the trammels of an antiquated 

 and misleading terminology ; and secondly, it impressed 

 them with the necessity of giving an answer to the 

 question how the multiplicity of sensations or the flow 

 of ideas was held together in the unity of an inner 

 existence. Thus it is a characteristic of all psycho- 

 physical writers who have come under the influence 

 of Herbart, that however much they may be occupied 

 with detailed description of physiological processes, with 

 the analysis of sensations or the dissection of the data 

 of experience, they never lose sight of the underlying 

 mental unity which is the central phenomenon of psy- 

 chology and of psycho-physics, just as it must be the 

 central problem of biology to arrive at some definition 

 of life. Had the investigations of psycho-physical pheno- 

 mena remained where Weber or even Helmholtz left 

 them, we should have brilliant chapters on the phenomena 

 of touch, of seeing, hearing, and other processes where 

 the outer and inner worlds come into contact, but no 

 attempt to sum up these brilliant contributions in a 

 connected view of the inner and higher life the most 

 remarkable and unique phenomenon in nature. It seems 



Unity of 



mental life, to me that, in Germany at least, it is through Herbart, 

 more than through any other thinker, that we have 

 been preserved from a threatening disintegration of 

 psychological research. It is the more necessary to 

 recognise this, as most of those writers who at one 

 time came greatly under Herbart's influence have found 

 it necessary, after having become thoroughly saturated 

 with this one great truth in his philosophy, to abandon 

 almost the whole of the more detailed expositions con- 



