CHAP, vi INSTINCT 67 



soon as it was seen that instinct, like other animal functions, 

 rested upon conditions many of which can be assigned, that 

 it does not spring into existence all at once in full per- 

 fection, but is subject, like other features of organic life, 

 to growth and change and possibly to decay, that it is not 

 always perfect or unerring, that no impassable gulf severs 

 it from intelligence, but rather that intelligence first arises 

 within the sphere of instinct when instinct was thus 

 brought into relation with more commonplace facts, the 

 awe and mystery surrounding it were dissolved, and the 

 central feature of animal psychology became susceptible of 

 scientific treatment. No one supposes that all instincts 

 are explained, or are easy to understand in the present 

 state of our knowledge. The central conception of instinct 

 itself is not as clearly defined as might be desired. But , 

 instinct is no longer a mysterious faculty which may at/ 

 once be set down as a sufficient explanation of anything inl 

 the behaviour of animals that we do not understand.^ 

 Instinctj:annot do anything and everything. It has limits 

 even if we have difficulties in drawing them with precision. 

 And secondly, its territory is not apart, but strictly con- 

 tinuous with other powers of organised beings. Instinct 

 in short is a product of evolution. It presides at a certain 

 phase, and has, all in due order, its beginning, its rise, its 

 culmination, and its decline. 



To give the full proof of what I have said would be 

 merely to repeat or summarise the works of authors far 

 more competent to deal with the matter than myself. I 

 may merely advert briefly to the abundant evidence showing 

 that instinct is not always perfect in its working ; that it 

 does not proceed on an unchangeable model ; that it is on 

 occasion applied mistakenly, uselessly and injuriously ; that 

 it is often incomplete at birth, and requires development ; 

 and that, at any rate among the higher animals, it is so 

 interwoven with intelligence that the two factors become 

 exceedingly difficult to disentangle. 



Nothing seems more instinctive than the impulse of the 

 young mammal to suck its mother's breast. Undoubtedly 

 there is an innate tendency to suck, and an impulse to suck 

 the breast. But there is no unerring inward guide leading 



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