MIND IN EVOLUTION 515 



inference ', some working with ideas. It is reflective and 

 inferential, as contrasted with instinctive and intuitive. 



When the Greek eagle lets a tortoise fall from a height 

 on the rocks below so that its strong carapace is broken, 

 when beavers cut a canal right through an island in a big 

 river a task not practically justified till completed, when 

 a collie dog at the bidding of a few sounds and signs 

 accomplishes a really difficult thing in the way of sheep- 

 driving, it is probable that we have to do with intelligent 

 behaviour. 



We have seen that, at various lower levels of behaviour, 

 the perfecting role of practice is recognisable, and this is 

 the case also at the level of intelligence. We are familiar 

 ' with the individual habituation of exercises which originally 

 required attentive selection and detailed control. Certain 

 structural changes in the nervous system come about as the 

 result of frequent performance, and what was at first la- 

 boured becomes very automatic or so facilitated up to a 

 certain point that the mind is free to attend to finishing 

 touches. It is not known that the results of individual 

 habituation can be entailed in a representative way on the 

 offspring. 



(i) The climax is the rational conduct occasionally ex- 

 hibited by Man. We cannot describe such conduct without 

 using general terms ; it involves experimenting with ideas, 

 conceptual as distinguished from perceptual inference; it 

 is controlled with reference to an ideal or conceived purpose. 

 Man has his reflexes and a little instinctive behaviour; 

 most of his activity is either intelligent, or was originally 

 intelligent, but has become habitual ; the point is that, if 

 occasion arise, Man may instantaneously pass from a lower 

 level to that of rational conduct. 



