616 Causes and Course of Organic Evolution 



natural for creatures to behave in this way that the existence 

 of any problem here is usually unsuspected; but this is the prob- 

 lem which confronts us when we endeavor to obtain a clear 

 understanding of the way in which intelligence develops out 

 of instinct." 



In next paragraph he then says: *'In the pleasure-pain re- 

 sponse we have two problems of a quite different nature — (1) the 

 problem of how behavior is modified by its results, and (2) the 

 problem of. why pleasure is associated with certain physio- 

 logical activities, such as securing movements; and pain with 

 others, such as avoiding movements. The latter prohlem is one 

 whose solution appears hopeless. [Ital. writer.] 



"Why then should pleasure be connected with one kind of 

 activity and pain with another.^ Why not just the reverse.^ 

 This problem is, I believe, insoluble, because it is a question 

 of the physical and the psychical." 



To all of the above, the writer would say that every cogitic — 

 like every cognitic and biotic — act represents a microchemical 

 change due to a definite expenditure of cogitic energy on a 

 definite micro-chemical substance. When such change works 

 in harmonious and rhythmic physical or chemical relation with 

 most or all of the other microchemical constituents of the 

 animal, satisfaction — as a result of most component stimuli 

 being in rhythmic harmony — or even pleasure — as a result of 

 complete harmonic rhythm — is the result. So pleasure might 

 be defined as: the harmonious and rhythmic agreement, in their 

 energized motion, of all molecular compounds of an animal, ivhen 

 these compounds are acted on by one or more stimuli.*' Pain 

 then is: the inharmonious relation in the energized motion of 

 definite molecular compounds, that compose the tissues of any 

 organism. 



Numerous illustrative examples of both from the human 

 organism might be given. Thus when a ripe pear or plum is 

 eaten the sweet taste to most is chemically satisfying to the 

 molecules of the taste sense endings, the soft mucilaginous sub- 

 stance starts another satisfying response, the contained sugar, 

 acid, and mucilage are all chemically satisfying to the fer- 



