DEGREES OF INTELLIGENCE. 



epochs of Descartes and Buffon,* the question of the instinct and 

 intelligence of animals was discussed in the spirit of the ancient 

 philosophy on purely metaphysical grounds. It was with Buffon, and 

 soon afterwards with Leroy, that it began to be placed upon the basis 

 of observation and induction ; but the first philosopher who reduced 

 it to a definite form and supported his reasoning by observations 

 systematically pursued was Frederick Cuvier. He proposed to de- 

 termine the limits of the intelligence of different species ; those which 

 separate intelligence generally from instinct ; and those in fine by 

 which human intelligence is distinguished from that of inferior 

 animals. These three points being once established, the long vexed 

 question of animal intelligence was presented under a new aspect. 



10. When Descartes and Buffon refused intelligence to animals, 

 they did so because they could not accord to them the same 

 faculty of intelligence which characterises the human race. Their 

 error therefore arose from not perceiving or not defining the limit 

 which separates human from animal intelligence. 



When Condillac and Leroy, on the contrary, falling into the 

 other extreme, accorded to animals the most elevated intellectual 

 powers, they did so because they overlooked the distinction 

 between instinct and intelligence. When they ascribed to intelli- 

 gence acts which were prompted by instinct, and therefore executed 

 with a perfection which, if they were the result of intelligence, 

 would require a very elevated degree of that faculty, they were 

 forced to admit in animals the possession of powers in some re- 

 spects even more elevated than those of the human race. 



11. The first observations of Frederick Cuvier indicated the 

 various degrees of intelligence in the different orders of mammifers. 

 Thus he found the highest development of that faculty in the 

 Quadrumana, at the head of which stand the chimpanzee and 

 ourang-outang. The second rank was assigned to the Carnivora, at 

 the head of which was placed the dog. The P achy dor mata stand 

 next, with the horse and the elephant at their head ; the two 

 lowest ranks consisting of the Ruminants and Rodents. 



12. Now it is important to remark that this classification of 

 mammifers according to their relative intelligence, based upon the 

 direct observation of their manners and habits, is found to be in 

 complete accordance with their cerebral development ; the organs 

 of the brain, which in man have been ascertained as being those 

 on which the intellectual functions depend, existing in a less and 

 less state of development as we descend from the Quadrumana 

 to the Carnivora, from the latter to the Pachydermata, and from 

 these successively to the Ruminants and Rodents. 



* Descartes published his "Discours sur la Methode" in 1637 ; and 

 Buffon published the "Discours sur la Nature des Animaux" in 1753. 



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