ai2 POPULAR SCIENCE MONTHLY. 



more than psychology can overlook the results established by biological 

 research. 



This becomes more evident in view of the fact that both mental and 

 .bodily life may and too often does vary from the course of normal 

 development. Those modifications which, either suddenly or gradually, 

 .reduce the mind to chaos, have in the past been studied chiefly on their 

 practical side. They possess none the less an interest for psychology. 

 By contrast at least they throw light on the normal activities of mind. 



It should be noted, however, that in mental pathology as in psycho- 

 2>hysics and in the study of normal development, comparison is simply 

 .a means of getting new information concerning those processes which 

 .appear in the normal individual consciousness. To render this informa- 

 tion available and to coordinate the multitude of facts which it con- 

 tains or suggests, some sort of theory is necessary; and there is no 

 lack of theorizing in modern psychology. 



Owing, perhaps, to the predominance of comparative methods, the 

 theory of psycho-physical parallelism is just now in vogue. It is 

 .agreed, in general, that mental processes and physical processes take 

 place simultaneously, and to this extent the one series may be said to 

 parallel the other. But beyond this, discussion is rife and the end is 

 not yet. If, on the more orthodox view, it is claimed that the two 

 .series are merely parallel, i. e.y without any causal nexus, it is urged on 

 the other hand, especially in these latter times, that there must be 

 interaction, mind producing effects in the organism and vice versa. 

 While, again, it is maintained that the conscious processes have causal 

 relations of their own — a specific psychical causality ; it is also asserted 

 that the causal relation exists for the physical processes only, and that 

 mind gets its connectedness as an accompaniment of the bodily series. 



The final adjustment of these claims may depend, in a measure, 

 upon the eventual acceptance or rejection of the hypothesis, now favor- 

 ably regarded, that every conscious state has for its organic basis the 

 passage from centripetal effects in the brain to centrifugal effects, and 

 consequently has its efferent or motor phase as well as its afferent or 

 sensory phase. This hypothesis, however, leaves untouched the inquiry 

 as to the precise way in which mind acts on body and body on mind. 

 The latter problem, in fact, is essentially metaphysical. It points at 

 once to the remoter region in which epistemology and criticism hold 

 •sway. 



More than any other science, psychology finds itself obliged to 

 -canvass its results in the light of philosophy. Of late the statement has 

 heen made quite frankly that the way to psychology has its starting- 

 point in philosophy. Be this as it may, psychology is, for the time 

 Deing, at the stage of self-examination, taking an account of its titles 

 vto existence as a science. Not that it doubts of its proper object; 



