80 The Outline of Science 



Animal Intelligence 



The higher reaches fif the inclined plane of behaviour show 

 intelligence in the strict sense. They include those kinds of be- 

 haviour which cannot be described without the suggestion that 

 the animal makes some sort of perceptual inference, not only 

 profiting by experience but learning by ideas. Such intelligent 

 actions show great individual variability; they are plastic and 

 adjustable in a manner rarely hinted at in connection with in- 

 stincts where routine cannot be departed from without the crea- 

 ture being nonplussed; they are not bound up with particular 

 circumstances as instinctive actions are, but imply an appreciative 

 Awareness of relations. 



When there is an experimenting with general ideas, when 

 there is conceptual as contrasted with perceptual inference, we 

 speak of Reason, but there is no evidence of this below the level 

 of man. It is not, indeed, always that we can credit man with 

 rational conduct, but he has the possibility of it ever within his 

 reach. 



Animal instinct and intelligence will be illustrated in another 

 part of this work. We are here concerned simply with the general 

 question of the evolution of behaviour. There is a main line of 

 tentative experimental behaviour both below and above the level 

 of intelligence, and it has been part of the tactics of evolution to 

 bring about the hereditary enregistration of capacities of effective 

 response, the advantages being that the answers come more 

 rapidly and that the creature is left free, if it chooses, for higher 

 adventures. 



There is no doubt as to the big fact that in the course 

 of evolution animals have shown an increasing complexity 

 and masterfulness of behaviour, that they have become at once 

 more controlled and more definitely free agents, and that the 

 inner aspect of the behaviour experimenting, learning, think- 

 ing, feeling, and willing has come to count for more and 

 more. 



