210 DOCTRINE OF EVOLUTION 



cell and sense-cell reflexes, an intelligent response is 

 quite as machine-like as any and all of its elements. A 

 difference in degree of complexity and extent is the only 

 thing that places intelligence apart from instinct and 

 reflex action, for the units are the same in all cases, 

 so far as science knows. 

 \ The apes are of the greatest value in providing the 

 transition from the grade of intelligence to the human 

 level where reason is found. Whether or not a chim- 

 panzee can reason at all is less important than the fact 

 that its total ''mental" powers are lower than those 

 of man, and higher than those of inferior mammalia. 

 Apes are far more susceptible to training than cats and 

 dogs, because their improved nervous mechanism en- 

 ables them to establish a psychological sequence with 

 greater facility. If we are to judge by the facts at hand, 

 these creatures possess a low order of mentality, like, 

 but by no means equivalent to, that of man. 



At the end of the comparative scale, we reach the 

 human mind which is characterized by its ability to 

 perceive and recognize far wider relations than those 

 which are involved in intelligence. Human conscious- 

 ness is the stream of thoughts and feelings which con- 

 stitute the immediate contents of mind. In our own 

 case, we know both the activities we perform and some 

 of the internal phenomena with which such activities 

 are connected. Then we are impelled to compare the 

 objective phenomena of action with the behavior of 

 other men and of lower organisms, and if their behavior 

 does not coincide with our own we are justified in believ- 

 ing that its direction lacks some of the elements we know 

 about in our own case. This is the method of compar- 



