108 MENTAL EVOLUTION IN ANIMALS. 



"^ tlie nervous system is not prophetic. It informs us of what 

 is its actual state at the moment, not what the after-effects of 

 that state will be. If we take sugar of lead, we receive at 

 first a pleasant sensation of sweetness, because the immediate 

 effect upon the nerves of taste is that of a healthy stimu- 

 lation. Later on, when the poison begins to work, we are 

 conscious of a painful sensation of griping, because the nerves 

 of the intestines are tlien being actually disintegrated by the 

 direct or indirect action of the irritant." 



Now if the doctrine before us is found to apply generally 

 f; to all cases of Pleasure and of Pain, the implication is suffi- 

 \ ciently apparent; Pleasures and Pains must have been 

 evolved as the subjective accompaniment of processes which 

 are respectively beneficial or injurious to the organism, and 

 so evolved for the purpose or to the end that the organism 

 should seek the one and shun the other. Or, to quote 

 Mr. Spencer, " if we substitute for the word Pleasure the 

 equivalent phrase — a feeling which we seek to bring into 

 consciousness and retain there, and if we substitute for the 

 word Pain the equivalent phrase — a feeling which we seek to 

 get out of consciousness and to keep out; we see at once 

 that, if the states of consciousness which a creature endeavours 

 to maintain are the correlatives of injurious actions, and if 

 the states of consciousness which it endeavours to expel are 

 the correlatives of beneficial actions, it must quickly disappear 

 through persistence in the injurious and avoidance of the 

 beneficial. In other words, those races of beings only can 

 have survived in which, on the average, agreeable or desired 

 feelings went along with activities conducive to the mainten- 

 ance of life, while disagreeable and habitually-avoided feelings 

 went along with activities directly or indirectly destructive of 

 life, and there must ever have been, otlier things equal, the 

 most numerous and long-continued survivals among races in 

 which these adjustments of feelings to actions were the best, 

 tending ever to bring about perfect adjustments. 



" If we except the human race and some of the highest 

 allied races, in which foresight of distant consequences intro- 

 duces a complicating element, it is undeniable that every 

 animal habitually persists in each act which gives j)leasure, 

 so long as it does so, and desists from each act which gives 

 pain. It is manifest that, for creatures of low intelligence, 

 there can be no other guidance." 



