lo Psychophysical Evolution 



as such, this is an open question, yet it is a gain of no little 

 importance that such a question may be set aside. The 

 equahty of facts becomes our rule so soon as we make the 

 problem of evolution a psychophysical one. We may 

 legitimately use such a combination of the mental and the 

 purely vital as that cited above — the case of recognition- 

 marks — without stopping to inquire in what sense a 

 mental fact, such as recognition, can have causal value 

 in the determination of purely physical characters in the 

 next generation. That may be discussed in psychology, 

 or in biology, and it must be discussed in genetic phi- 

 losophy ; but in a department in which the psychophysical 

 as such is the type of phenomenon expressly taken up for 

 examination, the divorce of the two, and even the recogni- 

 tion of a duahsm between them, is unwarranted. 



§ 3. Psychophysical Parallelism 



With the general understanding now arrived at, we 

 may take a preliminary survey of the field in the light of 

 certain current hypotheses. Among these is what is 

 known as ' psychophysical parallelism.' 



This principle, as ordinarily stated, supposes a thorough- 

 going concomitance between the two terms of the psycho- 

 physical relation, mind and body. It states the general 

 fact that certain changes in the organic, in those brain 

 and nerve processes with which consciousness is associated, 

 are always accompanied by changes in consciousness, and 

 also, that this last is a statement which can be converted — 

 so that it is also true that all changes in consciousness are 

 accompanied by organic changes, in the brain and nerves.^ 



1 Much embarrassment is likely to arise from confusion of terms, as the 

 problems of psychology and those of biology are brought into closest union. 



