168 EVOLUTION AND MAN S PLACE IN NATURE 



No true scientific advance can be made by reason 

 ing conducted on these lines. There are two theories 

 included, one of which must be abandoned if the other 

 is to be vindicated. If the object is to show that 

 there is no fundamental difference between man and 

 the higher mammals in their mental faculties/ it 

 seems implied that there is a fundamental difference 

 between man and the lower mammals, else there is no 

 need for drawing the line. On the other hand, if 

 mental powers are to be attributed to animals very 

 low in the scale/ we need some better understanding 

 of what is mental. Is there no fundamental differ 

 ence between man and such animals in their mental 

 faculties ? If there be none, the whole range of the 

 scale is before us, and the evidence must be stated 

 much more effectively than has yet been done. The 

 facts to be attributed to the sensori-motor system in 

 fishes, amphibians, and insects must be distinguished 

 from those facts in their life which are attributed 

 to mental faculties. No biologist has attempted this 

 needful distinction. If only we begin with fishes and 

 amphibians, and thence move downwards, the hope 

 lessness of the claim becomes manifest. This arises 

 from the impossibility of claiming, for animals lowest in 

 the scale, anything higher than powers of sensibility. 



If there were any considerable consensus of opinion 

 among scientific men, attributing intelligence to 

 animals very low in the scale, it would be inconsistent 

 to concentrate on exclusive references such as those 

 by which Darwin defined his object in the chapter on 

 the mental powers of man and the lower animals. The 

 definition of intelligence must be explicit, if any scien 

 tific conclusion is to be reached as to its appearance. 



